Download The role of OP insecticides in long-term declines of collembola and

DEPARTMENT for ENVIRONMENT, FOOD and RURAL AFFAIRS
Research and Development
CSG 15
Final Project Report
(Not to be used for LINK projects)
Two hard copies of this form should be returned to:
Research Policy and International Division, Final Reports Unit
DEFRA, Area 301
Cromwell House, Dean Stanley Street, London, SW1P 3JH.
An electronic version should be e-mailed to [email protected]
Project title
The role of OP insecticides in long-term declines of Collembola and the
importance of buffer zones for recovery
DEFRA project code
PN0934
Contractor organisation
and location
School of Biological Sciences (Dr G.K. Frampton)
University of Southampton
Bassett Crescent East
Southampton SO16 7PX
Total DEFRA project costs
Project start date
£ 117,786
01/07/00
Project end date
31/07/02
Executive summary (maximum 2 sides A4)
Key findings of the project
(1) Exclusion of an organophosphate insecticide (chlorpyrifos) from the outermost 6m edges of winter
wheat and/or grass crops was generally sufficient to protect non-target arthropods in the unsprayed
crop edges from effects of the insecticide. This applied both to a single chlorpyrifos application
monitored during one season and, with one exception, to repeated applications monitored over six
years.
(2) The exception was that when chlorpyrifos was first applied to a field that had not received insecticides
previously, springtail abundance at the unsprayed field edge declined temporarily. This was particularly
noticeable for Entomobrya multifasciata. However, subsequent annually-repeated chlorpyrifos
applications did not thereafter appreciably affect arthropods in the unsprayed field edge.
(3) The springtail Entomobrya nicoleti was eliminated from a field by chlorpyrifos applications but
monitoring revealed that populations in the unsprayed field edges were not adversely affected, either in
the short term or long term. The hypothesis that lack of recovery in the sprayed area of the field was
caused by adverse effects of chlorpyrifos on potential recolonists at the field edge therefore is not
supported.
(4) Protecting springtail communities in unsprayed crop edges appears ineffective as a means of assisting
the recovery of the species most vulnerable to organophosphate insecticides within sprayed areas. In a
winter wheat crop, counts of some Entomobryidae and Isotomidae, which had been reduced to near
zero by a chlorpyrifos application in early June, exhibited no evidence of recovery by the end of the
CSG 15 (Rev. 6/02)
1
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
study at crop harvest in August. This was despite the continued presence of the same species at high
abundance in an unsprayed crop edge at 10m distance away.
(5) Manipulation of the connectivity between a chlorpyrifos-sprayed wheat crop, unsprayed crop edge and
field boundary (hedgerow) using exclusion barriers provided evidence that the hedgerow may have had
a stronger influence than the unsprayed crop edge on the abundance and diversity of arthropods in the
sprayed area of crop. This suggests that the value of unsprayed crop edges in assisting recolonisation
of sprayed areas by non-target arthropods could depend strongly upon the type of field boundary
against which an unsprayed crop edge is sited.
Background and objectives
During the SCARAB Project (1990-1997), a pesticide regime that included organophosphate (OP) insecticides
was applied to an arable field under a grass and wheat rotation (Field 5, ADAS Drayton). Compared to a
reference area with lower pesticide inputs, the OP-based pesticide regime led to a long-term decline in the
abundance of Collembola (springtails), including the complete disappearance of the species Entomobrya
nicoleti. Monitoring up to 1999, four years after the last OP insecticide application, provided evidence of
varying degrees of recovery for different springtail species but not for E. nicoleti.
The objectives of this project are: (1) To determine whether use of OP insecticides has caused local extinction
of E. nicoleti in an arable field and its margins. Specifically, to test the hypothesis that lack of recovery in the
field may be explained by adverse effects of the pesticide regime on potential recolonists at the field edge. (2)
To determine whether use of OP insecticides, which had a substantial impact on field arthropod communities
during 1991 to 1997, negatively affected the springtail community of unsprayed 6m-wide buffer zones adjacent
to a hedgerow. (3) To investigate whether hedgerows and buffer zones are important as sources of springtail
recolonisation following OP insecticide use in arable fields. Following a DEFRA project review, this third
objective was broadened to include a wider variety of invertebrates.
Methods and principal findings
Objective 1
Suction samples were taken from Field 5 and its edges during 2000 to confirm whether any springtail recovery
had taken place and to test the hypothesis that the lack of recovery of E. nicoleti could be explained by a longterm impact of the pesticide regime on potential recolonists at the field edge (which was protected during all
insecticide applications by a 6m-wide unsprayed zone). When added to previous work, this monitoring
provided an eleventh consecutive year of arthropod data in Field 5.
Despite a change of field management to short-rotation willow coppice in 2000, high counts of E. nicoleti were
present in the field edges. The hypothesis that long-term use of OP insecticides had adversely affected the
abundance of potential recolonists therefore was rejected. A small number of individuals of E. nicoleti was also
found in the field, for the first time since 1995, although counts were substantially lower than those obtained
before the OP-based pesticide regime was applied.
Objective 2
Six years’ archived pitfall trap samples from the SCARAB Project were examined to determine counts and
distributions of arthropods in the crop edges of Field 5, adjacent to areas of the field that had received either
the OP-based pesticide regime or a lower intensity of pesticide inputs that excluded insecticides. This was to
investigate whether the substantial long-term impact of pesticide use on arthropods in the field during 1991 to
1997 also affected arthropods at the field edges.
The substantial, long-term declines of collembolan catches in the field were not duplicated at the field edge,
although a transient decline in collembolan abundance and species number at the field edge occurred
immediately after the first OP insecticide application during 1991. Despite being eliminated from the sprayed
area of the field, E. nicoleti populations were found to have persisted at the field edge.
CSG 15 (Rev. 6/02)
2
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
The combined findings from Objectives 1 and 2 indicate that major, long-term effects of broad-spectrum
insecticide use in the sprayed area of the field did not penetrate to the insecticide-free buffer-protected field
boundary. However, protection of field-edge collembolan populations appears to be ineffective as a means of
facilitating the recovery of the most vulnerable species within the sprayed area.
Objective 3
To investigate the importance of an insecticide-free crop edge as a source of arthropod recovery in the
adjacent sprayed crop, replicated barrier treatments were used to manipulate connectivity between the
sprayed crop, unsprayed edge and field boundary (hedgerow) in a winter wheat field in Hampshire in 2001.
The OP insecticide chorpyrifos was applied to the field in early June but was withheld from 6m-wide unsprayed
crop edges. Pesticide deposition was estimated using water-and-oil-sensitive targets placed in the sprayed
area and crop edges.
Ground-active arthropods were monitored using suction samples (12 dates) and pitfall traps (10 dates)
between late May and crop harvest (mid-August). Assessments of predation using artificial prey baits were
also carried out (9 dates). Samples were collected from replicated sections of the sprayed area that were
either isolated from the unsprayed crop edge, connected only to the unsprayed edge, or connected to both the
unsprayed edge and hedgerow. Additional samples were collected from within the unsprayed crop edge and
from sprayed and unsprayed locations in the centre of the field.
Samples taken from sprayed and unsprayed areas of the field indicated that the chlorpyrifos application had
affected non-target arthropods in the sprayed area as would be expected. Substantially lower arthropod counts
persisted in the sprayed area throughout the study, without evidence of recovery at crop harvest. Very little
chlorpyrifos deposition occurred in the unsprayed crop edges, and none was recorded 3m or more from the
sprayed area.
Suction and pitfall catches yielded higher arthropod counts in the sprayed area of crop connected both to the
unsprayed edge and hedgerow (‘fully-connected’), than in sprayed areas that were connected only to the
unsprayed edge (‘unsprayed-only’) or that were isolated from both the unsprayed edge and the hedgerow
(‘not-connected’). In all cases, where differences among the connectivity treatments were statistically
significant, catches were highest in the ‘fully-connected’ treatment; there were no consistent differences
between the ‘unsprayed only’ and ‘not connected’ treatments. Despite the relatively small spatial scale of the
study, three species of ground beetle, Agonum dorsale, Harpalus rufipes and Pterostichus madidus, were
significantly more abundant in ‘fully connected’ treatment on one or more sampling occasions, providing
evidence that the hedgerow influenced their recolonisation of the sprayed area to a greater extent than the
unsprayed crop edge.
The predation rate, assessed by the loss (i.e. removal by predators) of artificial prey baits, was significantly
higher in the ‘fully-connected’ area of sprayed crop than in the ‘not-connected’ area on one sampling date at
the end of the sampling period but did not differ significantly between the other treatments. There was a
tendency for springtails and pitfall-sampled ground beetles to be more abundant in the ‘fully-connected’
treatment, with no evidence of an inverse relationship between catches of springtails and their predators.
Possible explanations are discussed.
Following the insecticide application, overall arthropod suction catches in the sprayed crop area remained
significantly lower than those in the unsprayed crop edge until crop harvest in August, despite a distance of
only 10m between the sampling locations in the unsprayed edge and sprayed area.
CSG 15 (Rev. 6/02)
3
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Scientific report (maximum 20 sides A4)
Introduction
In regulatory risk assessment, an assumption is made that unsprayed crop edges are an important source of
recolonisation by non-target arthropods following pesticide applications (e.g. Forster & Rothert 1998). A recent
review found very little evidence to support this assumption, as the majority of studies of unsprayed crop
edges have so far have investigated their impact on invertebrates within crop edges rather than in the adjacent
sprayed part of the crop (DEFRA Project PN0939). There is evidence that some springtails and aphids recover
initially in the centre of sprayed areas, possibly as a result of the delayed arrival of their predators (Duffield &
Aebischer 1994) whereas other springtail species appear capable of movement inward from crop edges, at
least following disturbances such as tillage (Alvarez et al. 2000).
The MAFF SCARAB Project clearly demonstrated the long-term impact of organophosphate (OP) insecticide
use on arthropods in the field (Frampton 2001a; 2002). A pesticide regime containing OP insecticides (‘current
farm practice’, CFP) was compared with a regime of lower pesticide inputs (reduced input approach, RIA) that
avoided insecticides. These regimes were not replicated but comparison with baseline data and a novel spatial
switching of the regimes in 1997 provided unequivocal evidence that changes in arthropod abundance were
directly related to pesticide use (Frampton 2000a; 2001a). The CFP regime was applied initially to the west
half of Field 5 (ADAS Drayton) during 1991 to 1996 and then in spring 1997 it was switched to the east half of
the field, with a corresponding change of the RIA regime. The springtail Entomobrya nicoleti disappeared from
the west half of the field in 1991, then also from the east half of the field in spring 1997, without recovery in
either half having occurred by summer 1999 (Frampton 2000a). Abundance of other springtails, e.g.
Lepidocyrtus spp., also declined markedly, initially in the west and later in the east half of the field, coinciding
with the spatial changes in the pesticide regimes. This project investigated in Objective 1 whether springtail
recovery in the field had occurred by summer 2000 and whether populations of E. nicoleti were present at the
field edges. The latter is of interest because, if field-edge populations are a source of field recolonists,
penetration of effects of pesticides to the field edge could explain the poor recovery of some species in the
field. During all insecticide applications the outermost 6m of the field remained insecticide-free. Objective 2
investigated long-term changes in field-edge springtail communities adjacent to the CFP and RIA treated
areas of Field 5 during 1991 to 1996, to provide a test of the protective value of such unsprayed crop edges
against a regime of pesticide use that has been clearly demonstrated to be capable of causing major effects in
the field. These first two objectives were carried out using samples from Field 5 (new and archived,
respectively). Objective 3 involved an independent study in a field of winter wheat in Hampshire during 2001.
Manipulation of connectivity between the sprayed crop, unsprayed crop edges and adjacent hedgerows was
used to investigate the importance of the unsprayed edges and hedgerows as sources of arthropod
recolonisation of the sprayed area. Detailed accounts of the methods and results for objectives 1 and 2 are
given in an interim report on PN0934 Objective 1 (Frampton 2000b) and interim reports on Objective 2
(Frampton 2001b, c); the findings of objective 2 have also been published (Frampton 2002). Accordingly, brief
summary accounts are given below for Objectives 1 and 2, while Objective 3 is reported in detail.
Objective 1
1.1 Methods and Materials
On one date each in May, June and July 2000, D-vac suction samples were collected by staff at ADAS
Drayton from areas of Field 5 that corresponded to the former RIA and CFP pesticide regimes. Samples were
also collected adjacent to the field boundary bordering each half of the field. Full details of the study site, field
boundaries, husbandry and sampling protocol are given in an interim report on PN0934 Objective 1 (Frampton
2000b). Management of Field 5 during 2000 departed markedly from its previous arable/grass cropping; the
field was in its first year of short-rotation willow coppice. Power-harrowing had taken place during March 2000
but an uncultivated 6m-wide grass strip was left around the field perimeter. During the sampling period only
herbicides were applied to the cultivated area; these applications did not differ between the two halves of the
field.
CSG 15 (Rev. 6/02)
4
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
1.2 Results
Suction samples were processed at Southampton University; detailed results are given in the interim project
report on PN0934 Objective 1 (Frampton 2000b). The main finding was that counts of Entomobrya nicoleti at
the field edge in the uncultivated strip exceeded those found anywhere in the field on any of the previous
sampling dates during 1990-2000. Geometric mean counts were below 5 per 0.46m2 sample in the field but
ranged from 45 to 105 per 0.46m2 in the field edges (the difference between field and edges being significant
based on 95% CI ranges). There was no difference in the counts of E. nicoleti between the east and west
halves of the cultivated area, which had previously received the differing CFP and RIA pesticide regimes, or
between the east and west field edges. However the very low catches provide evidence of only marginal
recovery compared to suction catches obtained previously in the field (Frampton 2000a). A significant negative
correlation was found between the abundance of E. nicoleti and the congeneric E. multifasciata (Pearson
coefficient -0.8; P<0.0001), with the latter species being more abundant in the field than at the field edge.
Other collembolan groups (Lepidocyrtus spp., Orchesella villosa) that had previously been adversely affected
by the CFP pesticide regime also had higher abundance in the field than at the field edges.
1.3 Key conclusions
High counts of E. nicoleti at the edges of Field 5 show that the species was not adversely affected in the long
term by previous pesticide use under the CFP regime. The hypothesis that lack of recovery was caused by
lack of potential recolonists at the field edge therefore has to be rejected. The first records of E. nicoleti in the
cultivated area of the field since spring 1997 suggest that recolonisation had started, but counts remained
markedly lower than those that could be considered to represent full recovery. Other Collembola (e.g.
Lepidocyrtus spp.) were captured in numbers comparable with those seen prior to CFP pesticide use,
suggesting that, for these, full recovery had occurred.
Objective 2
2.1 Methods and Materials
The principle aim of this objective was to investigate whether leaving a 6m-wide unsprayed crop edge during
insecticide applications in Field 5 protected field-edge springtails from the known adverse effects of the CFP
pesticide regime in the sprayed area over a 6-year period (i.e. during administration of Field 5 within the
SCARAB Project; Frampton 2001d). A detailed account of the methods, results and conclusions has been
published, including a full description of the sampling protocol and all relevant pesticide applications (Frampton
2002). Accordingly, a brief overview is given here.
During the SCARAB Project, pitfall samples were collected at 0m, 10m, 75m and 150m into the CFP and RIA
areas of Field 5, where 0m represents samples adjacent to the field boundary. D-vac suction samples were
collected between 25m and 150m from the field boundary. As field-edge suction samples were not available,
pitfall samples collected from the field edge (0m) and field (75m) locations in the CFP and RIA areas of Field 5
were compared with suction catches obtained from the field to establish the reliability of using pitfall catches as
an estimate of collembolan abundance. Samples were taken on at least three dates in each year during 1990
(pre-treatment) and 1991-1996 (contrasting RIA and CFP pesticide regimes).
2.2 Results
A total of 25 pitfall sampling dates’ catches was examined, yielding 61,172 springtails. Other arthropods were
also identified and counted. The key finding was that although the initial imposition of the CFP regime in Field
5 in January 1991 had an initial negative impact on springtail abundance and diversity in field-edge samples,
for most species the long-term adverse effect of the CFP regime in the field did not extend to populations at
the field edge. In particular, E. nicoleti, which had disappeared from the CFP area of the field, was present
both in RIA and CFP field-edge samples in all years. Catches of Lepidocyrtus spp., which had also markedly
declined in the CFP area of the field, were similar for CFP and RIA field-edge samples, without any evidence
of a long-term impact of the CFP regime at the field edge. The strongest evidence for an effect of the CFP
CSG 15 (Rev. 6/02)
5
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
regime penetrating to the field edge was for Entomobrya multifasciata. This species was initially abundant but
declined to low counts in the CFP area of the field after the CFP regime was applied in January 1991
(Frampton 1997). Field-edge catches showed a similar pattern during 1991 to 1994, with zero counts in the
CFP edge until 1994, although counts at the RIA field edge were also low (usually < 10 per 0.46m2 sample).
The lack of catches of E. multifasciata at the CFP field edge persisted until 1994, after which catches at CFP
and RIA field edges were similar (Frampton 2001b). Results of multivariate (PRC) analyses of the collembolan
community responses support the conclusion that the CFP regime caused initial adverse effects on relative
abundance at the field edge but, for the community as a whole, these did not persist in the long term
(Frampton 2002). Comparison of pitfall and suction catches yielded remarkably similar patterns of counts and
species composition, suggesting that the pitfall catches gave an accurate indication of overall changes in
springtail abundance at the field edge.
2.3 Discussion and key conclusions
The field-edge springtail community did not escape adverse effects of the CFP pesticide regime, but effects
were clearly less pronounced than in the field. The most noticeable impact at the field edge was immediately
following implementation of the CFP regime in 1991. A lack of previous pesticide use for several years before
the CFP regime was applied (Young et al. 2001) might have resulted in a relatively stable arthropod
community, comprising species intolerant of disturbance (E. nicoleti as an example). The pesticide regimes
and cropping system in Field 5 are not typical of arable fields, but provide an intensive management regime
whose known, substantial, impact on field arthropod communities gives a valuable yardstick against which to
compare effects at the field edge. The fact that species very sensitive to OP insecticide use were not
substantially affected by the CFP regime at the field edge suggests either that the exclusion of all insecticide
applications from within 6m of the crop edge had an important protective role, or that ecological attributes of
field-edge populations reduce their long-term vulnerability (or a combination of the two). The latter might
include, for instance, protection from exposure by structurally diverse field-boundary vegetation. The findings
reported here support those from Objective 1 in confirming that E. nicoleti was present in the crop edge
despite disappearing from the CFP part of the field. They also confirm that field-edge populations of E. nicoleti
and some other springtail species do not appear to be effective as sources of recolonisation of OP-insecticide
sprayed areas.
Objective 3
3.1 Background
A recent review (DEFRA Project PN0939) found a lack of evidence on whether unsprayed crop edges assist
invertebrate recovery and the maintenance of biodiversity in pesticide-sprayed areas of crops. In particular,
there have been no robust studies on the impact of excluding individual insecticide products from crop edges.
The first two objectives of PN0934 confirmed that field-edge springtail populations may not be effective as
sources of population recovery in pesticide-sprayed areas, although there appears to be considerable interspecies variability both in initial effects and in subsequent recovery processes. It remains unclear whether
springtail recolonisation occurs from field edges and, if so, whether leaving crop edges unsprayed could assist
the process. Alvarez et al. (2000) demonstrated that isolating a spring barley crop from a hedgerow using
barriers caused statistically significant changes in the abundance of several surface-active springtail species
up to 30m into the crop, suggesting that colonisation of the field early in the season might occur by immigration
from the hedgerow. However, their work did not involve pesticides, and the influence of other factors such as
an indirect impact of predator exclusion could not be ruled out. Duffield & Aebischer (1994) showed that after a
dimethoate spray, recovery of some springtails commenced at the centre of the sprayed area, presumably as
a result of the delayed reinvasion of their macroarthropod predators. Another source of springtail recovery
might involve wind dispersal (Dunger et al. 2002), although this has not been investigated in agricultural
habitats.
The aim of this third objective of PN0934 was to investigate whether an unsprayed crop edge influences
populations of springtails in the sprayed area after a broad-spectrum insecticide application. Following a
DEFRA review of the project objectives, the sampling programme was broadened to include other
CSG 15 (Rev. 6/02)
6
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
invertebrates. Chlorpyrifos was chosen in view of its wide spectrum of activity against non-target arthropods,
especially springtails. If suitable spatial and temporal scales of monitoring are chosen it should be possible to
observe recovery in progress and determine whether an unsprayed crop edge contributes to the recovery
process. One option would be to monitor invertebrates in transects across sprayed fields that contain sprayed
and unsprayed crop edges. However, previous experience in which individual fields were used as replicate
monitoring units found substantial variation in springtail abundance and species composition among the fields,
even though they were contiguous, on the same soil type, shared boundaries, and had almost identical
cropping and agronomy histories (Frampton, 1999). To minimise such spatial and temporal ‘noise’, the design
chosen for the study aimed to enable relatively intensive spatial and temporal monitoring to be carried out at
relatively small spatial and temporal scales, within one field during one crop season. Replicated barrier
treatments were used to manipulate the connectivity of the sprayed crop area with an unsprayed crop edge
and adjacent field boundary; the barriers were used to overcome the problem of edge effects caused by the
movement of invertebrates. Such barriers have been shown to be effective at excluding ground-active
arthropods such as ground beetles, spiders (Holland 1998) and springtails (Gravesen & Toft 1987; Mebes &
Filser 1997) from experimental areas.
3.2 Methods and Materials
Study site. The work was carried out in summer 2001 in an 8ha field of winter wheat cv Maris Widgeon on the
Leckford Estate in Hampshire (51o7’N 1o2’W). The field was surrounded on all sides by a mature hedgerow. It
was selected in view of its homogeneity of crop cover and the relative uniformity of its boundary in terms of
physical and botanical structure. A section of the field edge was randomly selected for study, within which
three barrier treatments were each replicated four times, by assigning each treatment once (pseudo-randomly)
within each of four blocks. Two of the blocks were sited on one (south-east) edge of the field, with the
remaining two on an adjacent, perpendicular (north-west) edge. The orientations of the two edges were NWSE and SW-NE respectively. The south-east edge of the field bordered an a-8ha field of herbage seed (cv
Ronja) and the north-west edge bordered an orchard.
Connectivity treatments. Polythene exclusion barriers suspended on ropes strung between wooden posts
were erected in the field on 23 May. The barriers extended ca 30cm below ground and 90cm above. The
barriers were arranged spatially so as to provide the three experimental treatments (Fig. 1): (i) Barrier 6m from
the crop edge, parallel to hedgerow, to isolate the sprayed area of crop from a 6m-wide unsprayed crop edge;
(ii) Barrier adjacent, and parallel, to the hedgerow to provide connectivity between the sprayed area and
unsprayed crop edge, but no connectivity with the hedgerow; and (iii) No barrier – to provide full connectivity
between sprayed crop, unsprayed crop edge and hedgerow. These treatments are designated, respectively,
C0 (no connectivity), C1 (connectivity with unsprayed edge) and C2 (connectivity with unsprayed edge and
hedgerow). Each barrier was 12 m wide, with adjacent barrier treatments separated by barriers running
perpendicular to the hedgerow up to 20 m into the crop (Fig. 1). In this study design, the connectivity
treatments, but not the insecticide spray, were replicated. This overcomes the problem of chemical drift
affecting adjacent treatment units, as may have happened in other work (e.g. PS0918).
CSG 15 (Rev. 6/02)
7
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Fig. 1 . Study design (not to scale)
sampling locations
Connectivity of
sprayed area:
13m
s suction samples (n=4)
p pitfall traps (n=5)
C2
s+p
C1
s+p
barriers
C0
s+p
sprayed
area
6m
3m
unsprayed
crop edge
(Buffer)
s
0m
hedgerow
12m
Invertebrate sampling. Five pitfall traps (white plastic cups,  9cm, depth 15cm) were sited 1-m apart in the
centre of each plot, 13m into the crop from the hedgerow (7m into the sprayed crop area) (Fig. 1). These traps
were operated ‘wet’, i.e. they each contained a ca 5cm depth of water and a drop of household detergent to
break the surface tension. Traps were emptied on a weekly basis from mid-June to mid-August on 10
sampling occasions, giving an almost unbroken trapping sequence from 6 June to 15 August. Suction samples
were at approximately weekly intervals on 12 sampling occasions from 25 May to 14 August (immediately prior
to crop harvest) using a Ryobi machine similar to one described by Macleod et al. (1994). On each occasion,
four samples were taken from random locations within each plot between 2m and 4m from the hedgerow
(‘Buffer’ samples from the unsprayed crop edge) and between 12m and 14m from the hedgerow (C0, C1 and
C2 samples from 6m-8m into the sprayed crop). On each sampling occasion, four randomly-placed suction
samples were also collected ca 80m from the hedgerow in the spayed and unsprayed halves of the field to
confirm effects of the insecticide spray and enable comparisons with field-edge samples. Ryobi suction
sampling followed the same procedure described by Frampton (1999). All samples were taken between crop
plants to avoid the possibility of sampling efficiency being affected by vegetation. The order of sampling plots
was varied between sampling dates to minimise any within-date temporal bias in sample collection. For
preservation, samples were transferred into ca 70% industrial methylated spirit in the field where possible, or
stored in a freezer (suction samples) or cold room (pitfall catches) prior to preservation. All samples collected
on the same date were treated similarly, to avoid handling bias. In addition to arthropod sampling,
assessments were also made of crop growth stage, crop height and vegetation ground cover in the study
plots, and vegetation composition of the hedgerow and its base.
Predation assessments. Freeze-killed pupae of Drosophila melanogaster were obtained from laboratory
cultures and were attached at regular spacing to the rough side of 14cm × 12cm cards of medium-grade wet
and dry abrasive paper using flour and water paste. On most occasions 30 pupae per card were used. Cards
of pupae (usually three per treatment plot) were placed in the field ca 13m from the hedgerow, adjacent to
pitfall traps (see above). The cards were placed with the pupae uppermost, to prevent pupae falling off, and
were shielded from rainfall by 15cm-square metal covers supported ca 3cm above the ground on narrow legs
to permit easy access of arthropods. Predation assessments were made on nine occasions during the
summer, with pupae remaining in the field each time for 24-hour periods. On each occasion the number of
pupae remaining and the number damaged were recorded, as well as any evidence for slug presence. Cards
that had been visited by slugs were excluded from analysis because slugs can remove Drosophila pupae.
Insecticide application and estimation of spray deposition. Chlorpyrifos (480 g l-1 EC) was applied to the
field on 6 June using a Chafer E-Series tractor-drawn sprayer with a 28-m wide boom comprising 56 Teejet
80o flat fan nozzles (XR 80 03) at 0.5m-spacing. A volume rate of 200 l ha-1 was obtained with a boom height
CSG 15 (Rev. 6/02)
8
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
of 46cm, operating pressure of 2 bar and forward speed of 11 km h-1. The 4-ha half of the field containing the
connectivity treatments was sprayed except for the outermost 6m of crop; the remaining 4ha of the field
furthest from the study treatments was not sprayed. The distance between the study plots and unsprayed half
of the field was greater than 150m; half of the field was left unsprayed to permit an (unreplicated) evaluation of
the impact of the chlorprifos application on non-target arthropods at the field centre. The spray application took
place between 1600 and 1630 BST in dry, sunny weather, during which time the screen temperature was 19oC
and the wind was SW to SSW, ca 8-10 km h-1. Immediately prior to the spray application, Teejet water-andoil-sensitive paper strips (2.5 × 7.5 cm) were placed in each of the connectivity treatment plots to enable an
estimate of spray deposition. Strips were placed on the ground and at crop height (0.9m above the ground,
each supported on a wooden stake) at 0m, 3m, 5.5m and 13m from the hedgerow; one strip was used at each
height and distance in each of the 12 study plots (total 96 strips). After the spray application the strips were
allowed to dry and were each wrapped individually in foil to prevent contamination. Droplet deposition on the
strips was measured using image analysis software and deposition rates of chlorpyrifos (μl cm-2) were
estimated using laboratory-prepared calibration curves.
Other pesticide applications. A tank mix of fungicides was applied to the whole field on 11 June and was not
excluded from the edges. This application represented standard agricultural practice and comprised
epoxiconazole + fenpropimorph + kresoxim-methyl and quinoxyfen.
Data analysis. Arthropod counts were analysed using mixed model analyses of variance, with treatment as a
fixed factor and block as random factor. Treatment × block interactions were included in the model. In cases
where the interaction was significant (P<0.05), arthropod counts in the four blocks were examined graphically
to determine whether a consistent pattern of treatment effects was present across all blocks; in cases where
the interaction was clearly caused by one of the three treatments, data were re-analysed with that treatment
excluded. If treatments differed significantly (P<0.05), Tukey HSD multiple comparison tests were used to
identify the significant differences. Data were transformed where necessary prior to analysis to ensure that
they did not deviate significantly from normality and that variances were homogeneous. Usually, a log (x+1)
transformation of the counts, x, was sufficient. For analysis of the proportions of pupae removed in the
predation experiments, the proportions were arcsine-transformed prior to analysis. Community-level analyses
of the arthropod responses to the connectivity treatments were carried out using the multivariate technique
PRC analysis (e.g. van den Brink & Ter Braak 1999). Due to the large number of springtails captured, it was
not possible to accurately identify all specimens. In particular, Isotoma viridis and I. anglicana could not be
separated and reported here as Isotoma ‘viridis group’.
3.3 Results
Chlorpyrifos deposition. Analysis of the water-and-oil-sensitive strips showed that no chlorpyrifos deposition
occurred at 0m and 3m from the hedgerow, either at crop height (0.9m) or on the ground. Estimated deposition
at the edge of the unsprayed crop edge near to the sprayed area (5.5m from the hedgerow) ranged from 0 to
0.24 μl cm-2 on the ground and 0 to 0.25 μl cm-2 at crop height. In the sprayed area, 13m from the hedgerow,
deposition on at crop height (1.57 to 1.97 μl cm-2) was consistently greater than that on the ground (0.59 to
1.02 μl cm-2) (Fig. 2). Deposition did not differ significantly between the three connectivity treatments for any
combination of distance (5.5m or 13m) and height (crop or ground) (in all cases F2, 9 < 0.67, P>0.5). Deposition
5.5m from the hedgerow did, however, vary between the experimental blocks, with little or no chlorpyrifos
reaching the ground in blocks 3 and 4 compared with blocks 1 and 2 (Fig. 2). These two pairs of blocks were
at different field boundaries, aligned perpendicular to one another; the lack of chlorpyrifos reaching the ground
probably reflects an effect of the wind direction, as crop height and growth stage were remarkably uniform
across all blocks.
CSG 15 (Rev. 6/02)
9
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Fig. 2. Chlorpyrifos deposition in the study plots
C h lo r p y r if o s d e p o s it io n a t c r o p h e ig h t ( 0 .9 m )
5 .5 m
fr o m
h e d g e ro w
1 3 m
fr o m
C 0
C 1
h e d g e ro w
2 .0
Estimated
deposition
-2
(μl cm )
1 .5
1 .0
0 .5
0 .0
C 0
C 1
C 2
C 0
Block 1
C 1
C 2
Block 2
fr o m
C 0
h e d g e ro w
C 1
C 2
Block 4
Block 3
C h lo r p y r if o s d e p o s it io n o n t h e
5 .5 m
C 2
g ro u n d
1 3 m
fr o m
C 0
C 1
h e d g e ro w
1 .5
Estimated
deposition
-2
(μl cm )
1 .0
0 .5
0 .0
C 0
C 1
Block 1
C 2
C 0
C 1
C 2
Block 2
Block 3
C 2
C 0
C 1
C 2
Block 4
Suction catches. A total of 119,590 arthropods was captured and identified in the suction samples, of which
98,758 (83%) were springtails (Collembola). Suction catches comprised 8 species of ground beetle
(Carabidae), 3 groups of rove beetle (Staphylinidae), 5 groups of fungus beetles (Lathridiidae), 15 groups of
other beetles (Coleoptera), 4 groups of bugs (Hemiptera), 3 groups of spiders (Araneae), 20 groups of
springtails (Collembola) and 7 other arthropod groups (65 groups monitored in total). Suction catches from the
sprayed and unsprayed areas of the field clearly demonstrate a negative impact of the chlorpyrifos application
on arthropods, without recovery by the end of the monitoring period (Fig. 3). Entomobrya nicoleti, a species of
interest in Objectives 1 and 2 (above), was not present at the Hampshire study site, either in the field or its
edges.
The largest differences in catches were generally the unsprayed crop edge (buffer) and the sprayed area;
differences among the three connectivity treatments were relatively small by comparison (Fig. 4). Three
patterns are recognisable: (1) counts consistently higher in the unsprayed edge (most arthropod groups), (2)
counts not different in the unsprayed edge and the sprayed area (e.g. Araneae), and (3) counts lower in the
unsprayed edge compared to the sprayed area (e.g Carabidae, Corticariinae (Lathridiidae) and Lathridiidae
larvae) (Fig. 4). For many taxonomic groups there were significant interactions between treatment (i.e.
sampling location C0, C1, C2 or Buffer) and block. The statistically significant treatment effects shown in Fig. 4
are those for which the treatment × block interaction was not significant (P>0.05). In all cases where
differences between the connectivity treatments (C0, C1, C2) were significant, the difference involved a higher
catch in the fully-connected treatment (C2). This was also reflected in the taxonomic richness (Fig. 4).
Accumulated summer suction samples for the 11 sampling dates that followed the application of chlorpyrifos
(Fig. 5) showed that the largest overall differences in catches were between the unsprayed crop edge and the
sprayed crop area. For some groups, e.g. the springtails Pseudosinella spp. there was no consistent pattern of
CSG 15 (Rev. 6/02)
10
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
catches between any of the sampling locations (Fig. 5). However, the springtail Orchesella villosa, the total
Collembola and the total arthropods were significantly more abundant over the summer as a whole in the fullyconnected treatment (C2) than in the sprayed area that was isolated from the unsprayed edge  hedgerow
(C0, C1) (Fig. 5). Consistent with the patterns seen on individual sampling dates, the accumulated catches of
some groups were higher in the sprayed crop than in the unsprayed crop edge (Isotomurus spp.,
Staphylinidae, Corticariinae and Lathridiidae larvae), although the difference was statistically significant only
for Corticariinae.
Fig. 3. Suction catches of arthropods in the sprayed and unsprayed areas of the field 80m from the hedgerow.
Arrows indicate timing of the Insecticide application.
Isotoma viridis 'group'
Unsprayed
Lepidocyrtus spp.
Sprayed
300
250
200
200
150
150
100
100
50
50
0
0
Total Collembola
Total arthropod catch
400
500
400
300
300
200
200
100
100
0
0
25
05
CSG 15 (Rev. 6/02)
08
06
12
06
19
06
24
06
29
06
04
07
11
07
16
07
22
07
31
07
25
05
14
08
11
08
06
12
06
19
06
24
06
29
06
04
07
11
07
16
07
22
07
31
07
14
08
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Fig. 4. Suction catches of arthropods in an unsprayed crop edge (Buffer) and at 7m into the sprayed
area under three levels of connectivity with the unsprayed edge (C0, C1, C2; details in text). Arrows
Indicate time of insecticide application. ‘>’ indicates direction of significant differences.
Total Carabidae
Aphididae
C0
C1
C2
C0
Buffer
120
100
80
60
40
20
0
800
* P=0.001
600
Buffer > C0, C1, C2
400
200
0
*
* P=0.041
C2
Buffer
C2 > Buffer
*
*
Delphacidae
C0
120
100
80
60
40
20
0
C1
C1
Corticariinae (Lathridiidae)
C2
+ P=0.013
Buffer
C0
C2
Buffer
150
* 0.008 < P < 0.048
Buffer > C0, C2
C1
* 0.001 < P < 0.05
Buffer > C0, C1, C2
100
C0, C1, C2 > Buffer
50
0
+
*
*
*
C1
C2
*
*
Lathridius spp. (Lathridiidae)
Total Hemiptera
C0
* *
C0
Buffer
C1
C2
Buffer
20
800
* 0.001 < P < 0.004
600
* P=0.01
15
Buffer > C0, C1, C2
Buffer > C0, C1, C2
400
10
200
5
0
0
*
*
*
*
Lathridiidae larvae
Total Staphylinidae
C0
C1
C2
C0
Buffer
C1
C2
250
200
150
+ P=0.001
* P=0.029
200
Buffer
C0, C1, C2 > Buffer
Buffer > C0, C1, C2
150
100
100
50
50
0
0
25
05
CSG 15 (Rev. 6/02)
08
06
12 19 24 29 04 11 16
06 06 06 06 07 07 07
22
07
14
08
31
07
12
25
05
*
+
08 12 19 24 29 04 11 16
06 06 06 06 06 07 07 07
22
07
31
07
14
08
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
Project
title
DEFRA
project code
PN0934
Fig. 4 (continued)
Total Araneae
C0
300
250
200
150
100
50
0
C1
* P=0.001
Lepidocyrtus spp. (Entomobryidae)
C2
Buffer
C0
* P=0.001
2500
Buffer, C2 > C0
C1
C2
Buffer
Buffer > C0, C1, C2
2000
1500
1000
500
0
*
*
Total Symphypleona
C0
C1
Isotoma 'viridis group' (Isotomidae)
C2
Buffer
C0
2500
C1
C2
Buffer
C2
Buffer
1500
2000
* P=0.001
1500
Buffer > C0, C1, C2
C2 > C0
1000
1000
500
500
0
0
*
Total Collembola
C0
C1
Total Catch
C2
Buffer
C0
8000
C1
8000
6000
6000
4000
4000
2000
2000
0
0
Mean number of taxa per sample
C0
* P=0.001
40
C1
C2
Total Catch excluding Collembola
Buffer
C0
1200
1000
800
600
400
200
0
Buffer > C0, C1, C2
30
20
10
+ P=0.001
0
*
25
05
CSG 15 (Rev. 6/02)
C2 > C0, C1
* * * * * *
++
08 12 19 24 29 04 11 16
06 06 06 06 06 07 07 07
22
07
*
*
31
07
14
08
13
C1
C2
Buffer
* P=0.001
Buffer > C0, C1, C2
C2 > C0
*
25
05
08
06
12 19 24 29 04 11 16
06 06 06 06 07 07 07
22
07
31
07
14
08
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Fig. 5. Accumulated summer suction catches of arthropods in an unsprayed crop edge (Buffer) and
at 13m from the hedgerow (7m into the sprayed area) under three levels of connectivity with the
unsprayed edge (C0, C1, C2; details in text). ‘>’ indicates direction of significant differences.
Isotoma 'viridis group' ( Isotomidae) (Log scale)
Orchesella villosa (Entomobryidae) (Log scale)
C0
10000
C1
C2
C0
Buffer
P=0.001 Buffer > C0, C1, C2; C2 > C0, C1
C1
Buffer
P=0.001 Buffer > C0, C1, C2
10000
100
C2
100
1
1
Block1
Block2
Block3
Block4
Block1
Lepidocyrtus spp. (Entomobryidae) (Log scale)
C0
C1
C2
Block2
Buffer
C0
C1
C2
P=0.001 Buffer > C0, C1, C2
100
1
Block3
Block4
Block1
Block2
Pseudosinella spp. (Entomobryidae)
C0
C1
C2
Buffer
P>0.05
800
600
400
200
0
Block2
Block4
Isotomurus spp. (Isotomidae)
10000
Block1
Block3
Block3
Block4
Total Collembola
Buffer
C0
No test (Treatment × Block P=0.001)
3000
2500
2000
1500
1000
500
0
15000
C1
C2
Buffer
P=0.001 Buffer > C0, C1, C2; C2 > C1, C0
10000
5000
0
Block1
Block2
Block3
Block1
Block4
Sm inthurinus spp. (Symphypleona) (Log scale)
C0
C1
C2
Block2
Block3
Block4
Total Collembola excluding Pseudosinella spp.
Buffer
C0
P=0.001 Buffer > C0, C1, C2
C1
C2
Buffer
P=0.001 Buffer > C0, C1, C2
10000
12000
8000
100
4000
1
0
Block1
CSG 15 (Rev. 6/02)
Block2
Block3
Block4
Block1
14
Block2
Block3
Block4
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
Fig. 5 (continued)
Total Staphylinidae
C0
C1
C2
Total Hemiptera
Buffer
C0
P>0.05
200
150
100
50
0
C1
C2
Buffer
P=0.001 Buffer > C0, C1, C2
1500
1000
500
0
Block1
Block2
Block3
Block1
Block4
Block2
C1
C2
C0
Buffer
P=0.01 C2 > Buffer
200
150
100
50
0
Block1
Block2
Block3
C1
C2
Block1
Block4
C1
C2
Block2
Block3
Block4
Total Catch
Buffer
C0
P>0.05
150
Buffer
P>0.05
500
400
300
200
100
0
Total Carabidae
C0
Block4
Linyphiidae + Erigonidae
Corticariinae (Lathridiidae)
C0
Block3
15000
100
10000
50
5000
C1
C2
Buffer
P=0.001 Buffer > C0, C1, C2; C2 > C0, C1
0
0
Block1
Block2
Block3
Block1
Block4
C0
C1
C2
Block3
Block4
Total catch excluding Collembola
Total Coleoptera
500
400
300
200
100
0
Block2
C0
Buffer
P>0.05
C1
C2
Buffer
P=0.01 Buffer > C0, C1
2500
2000
1500
1000
500
0
Block1
CSG 15 (Rev. 6/02)
Block2
Block3
Block1
Block4
15
Block2
Block3
Block4
PN0934
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Pitfall catches. A total of 16,673 arthropods was captured and identified in pitfall traps, comprising 25
species of ground beetle (Carabidae), 9 groups of rove beetle (Staphylinidae), 19 other beetle (Coleoptera)
families and three groups of spiders (Araneae) (56 groups monitored in total). Spiders made up 67% of the
overall catch and beetles 33%. Several groups of arthropods had differences in catches between the
connectivity treatments on individual sampling dates (Fig. 6). These were all ground beetles (Carabidae). In all
cases where the differences were statistically significant, the catches were higher in the sprayed crop area
connected to both the unsprayed edge and hedgerow (C2); there were no consistent differences between
sprayed crop areas fully isolated (C0), or those connected only to the unsprayed edge (C1) (Fig. 6). Some of
the treatment differences shown in Fig. 6 appear substantial, however on most sampling occasions there were
strong spatial interactions, which is why relatively few of the treatment contrasts were significant. Summed
pitfall catches for the 10 sampling dates are presented for each block in Fig. 7 and show the spatial variability
of catches over the summer as a whole. Pterostichus madidus, for instance, was more abundant in blocks 1
and 2 (adjacent to the SE field edge) than in blocks 3 and 4 (adjacent to the NW edge). Nevertheless,
accumulated catches of P. madidus and some other groups exhibited significant effects of the connectivity
treatments. For P. madidus, Harpalus rufipes, the total Carabidae and total Coleoptera there was a clear
pattern of higher catches in the C2 treatment in all blocks (Fig. 7). Not all species were more numerous in
traps in the C2 treatment: catches of Bembidion lampros and Lycosidae were markedly higher in the
unconnected part of the sprayed crop (C0) on some occasions, however these differences were neither
spatially (Fig. 7) nor temporally consistent.
Predation. Predation rates on the first two sampling dates could not be analysed statistically due to an
inadequate number of baited cards, as several cards were discarded due to slug presence. Pupal loss
increased during June and then tended to remain broadly similar for subsequent sampling occasions,
fluctuating between 30-50% of the available pupae (Fig. 8). During August there was a tendency for rates of
pupal loss to be higher where full connectivity was maintained with the unsprayed crop edge and hedgerow
(C2) than where connectivity was not maintained (C0, C1) (Fig. 8). Analysis of the differences among the three
treatments yielded no significant treatment effects. However, on the final sampling occasion (15 August), rates
of pupal loss in C2 were consistently higher than in C0 for all blocks and this difference was statistically
significant if C1 was excluded from the analysis (F1,3=59.8, P=0.004).
3.4 Discussion
Pesticide application. The deposition estimates show that chlorpyrifos did not reach as far as the middle of
the 6m-wide unsprayed crop edge and, in some cases, it did not penetrate as far as 0.5m into the unsprayed
edge. Accordingly, there was a clear contrast in insecticide deposition between the sprayed crop area and the
unsprayed crop edge. The chlorpyrifos application was not replicated but suction catches taken 80m into the
crop clearly demonstrate declines in arthropod abundance following the spray, without obvious recovery during
the study. Fungicide applications made on 11 June were applied to the whole field as standard farm practice
and are typical of pesticide applications made to winter wheat in summer. Their impact on the arthropods
could not be specifically assessed with this study design, but any interaction between the use of chlorpyrifos
and fungicides would have been realistic in scale and do not influence the conclusions of this work.
In the current study, comparisons were not made with chlorpyrifos-sprayed crop edges because much larger
spatial scales of study would have been required, to enable adequate replication and to allow for intertreatment buffer areas (to prevent cross-contamination of treatments by spray drift and/or arthropod
redistribution). Historically, attempts to monitor effects of crop-edge pesticide manipulation on invertebrates in
sprayed areas at realistic spatial scales have tended to run up against three problems: (1) limited replication;
(2) infrequent temporal monitoring; and (3) problems of edge-effects caused by the use of experimental study
units that are too small. Accordingly, very little robust information exists on how crop-edge pesticide
manipulation influences invertebrates in sprayed areas (DEFRA PN0939). Recent work has shown that
intensive within-field monitoring can provide valuable information on arthropod distribution dynamics at spatial
scales relevant to agricultural management practices (Thomas et al. 2002) but available resources rarely
permit such studies to be replicated. Conversely, transect monitoring approaches employing large spatial
scales (e.g. with whole fields as replicates) that have been used to investigate effects of crop-edge pesticide
CSG 15 (Rev. 6/02)
16
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
manipulation have tended to have limited temporal sampling. The problem of insecticide drift between
experimental study areas was avoided in the current work, as the study design did not require replication of
the insecticide application.
Fig. 6. Pitfall catches of arthropods (per 5 traps per 7d) at 13m from the hedgerow (7m into
the sprayed crop area) under three levels of connectivity with the unsprayed crop edge
(C0, C1, C2; details in text). ‘>’ indicates direction of significant differences between treatments
Agonum dorsale
C0
60
C1
C2
*
* P=0.001
40
C2 > C0, C1
20
0
13
20
27
4
10
19
26
1
9
15
Harpalus rufipes
C0
60
C1
C2 > C0, C1
C2
*
+
40
* P=0.045
+ P=0.045
C2 > C1
20
0
13
20
27
4
10
19
26
1
9
15
Pterostichus m adidus
C0
60
C1
C2
* P=0.001
*
C2 > C0, C1
40
20
0
13
20
27
4
10
19
26
1
9
15
Total Carabidae
+
300
C0
C1
* P=0.022 C2 > C0
+ 0.009 < P < 0.013 C2 > C1
C2
200
100
+
*
26
1
X
P=0.022
C2 > C0, C1
X
0
13
20
27
4
10
19
9
15
Total arthropod catch
C0
1000
800
600
400
200
0
C2
* P=0.048
*
13
20
June
CSG 15 (Rev. 6/02)
C1
27
4
10
19
July
26
1
C2 > C1
9
August
17
15
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Fig. 7. Accumulated summer pitfall catches of arthropods at 13m from the hedgerow (7m into the
sprayed crop area) under three levels of connectivity with the unsprayed crop edge (C0, C1, C2;
details in text). ‘>’ indicates the direction of significant differences.
Agonum dorsale
C0
C1
Pterostichus madidus
C2
100
80
30
P>0.05
P=0.012 C2 > C0, C1
60
20
40
10
20
0
0
Block1
Block2
Block3
Block1
Block4
Bembidion lampros
Block2
Block4
Trechus quadristriatus
P>0.05
80
Block3
P>0.05
50
40
60
30
40
20
20
10
0
0
Block1
Block2
Block3
Block4
Block1
Bembidion obtusum
30
300
20
200
10
100
0
0
Block2
Block3
Block4
P=0.002 C2 > C0, C1
400
Block1
Block3
Total Carabidae
P>0.05
40
Block2
Block1
Block4
Block2
Block3
Block4
Mean number of carabid species
(averaged over all sampling dates)
Harpalus rufipes
P=0.043 C2 > C0, C1
P=0.028 C2 > C0, C1
120
100
80
4
3
60
40
20
0
2
1
0
Block1
CSG 15 (Rev. 6/02)
Block2
Block3
Block4
18
Block1
Block2
Block3
Block4
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Fig. 7 (continued)
Total Coleoptera
Chrysomelidae
C0
C1
P=0.015 C2 > C0, C1
C2
600
500
400
300
200
100
0
P>0.05
40
30
20
10
0
Block1
Block2
Block3
Block1
Block4
Cryptophagidae
Block3
Block4
Block3
Block4
Lycosidae
P>0.05
50
Block2
P>0.05
150
40
100
30
20
50
10
0
Block1
Block2
Block3
0
Block4
Block1
Block2
Linyphiidae + Erigonidae
Lathridiidae
P>0.05
P>0.05
1000
80
800
60
600
40
400
20
200
0
0
Block1
Block2
Block3
Block1
Block4
Total Staphylinidae
Block2
Block3
Block4
Total arthropod catch
P>0.05
P>0.05
1000
1600
800
1200
600
800
400
400
200
0
0
Block1
CSG 15 (Rev. 6/02)
Block2
Block3
Block4
19
Block1
Block2
Block3
Block4
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Fig. 8. Predation rates (proportion of artificial prey removed) in insecticide-sprayed crop areas that
differed in their connectivity to an unsprayed crop edge and hedgerow (C0, C1, C2; details in text).
C 0
C 1
C 2
0.6
0.5
Mean proportion
of available
0.4
prey removed
0.3
0.2
0.1
0.0
19
27
5
10
June
19
July
27
3
9
15
August 2001
Study design. The relatively small spatial scale of this study was driven by the initial aim of investigating
whether horizontal movement of springtails occurs from the unsprayed crop edge into the sprayed crop area
following a broad-spectrum insecticide application. Springtail communities are particularly vulnerable to effects
of chlorpyrifos (e.g. Frampton 1997, 1999, 2000a), with little or no recovery observed for some species within
the same crop season, although recovery dynamics seem to vary considerably among species (see Objectives
1 and 2 above). If the source of recovery is at the field edge, frequent (ca weekly) monitoring relatively close to
the field edge should detect any recovery of surface-active springtails that occurs in the sprayed area. The
connectivity treatments employed here were designed to permit determination of the relative importance of the
hedgerow and unsprayed crop edge compared to the field as sources of recovery. The barriered plots used in
the study were open-ended, with free movement of arthropods possible at the end situated in the sprayed crop
(Fig. 1). This was to avoid unequal enclosure sizes that would have affected arthropod community dynamics. If
recovery was entirely from the field, no difference in catches would be expected between the connectivity
treatments. However, if the unsprayed crop edge or hedgerow contributed to recovery, catches would be
expected to vary with the connectivity to the sprayed area.
For springtails that are adversely affected by chlorpyrifos, especially members of the Entomobryidae, it is
reasonable to assume that individuals recolonising from the field edge by cursorial activity would not be able to
disperse from one experimental treatment to another, as barriers extended 20m into the crop. Springtails that
recover in situ in the field (or which are not adversely affected by chlorpyrifos) would not be expected to differ
in their abundance between the connectivity treatments. For species which recover more quickly, frequent
sampling at weekly intervals aimed to ensure that transient differences between the connectivity treatments
should be detectable (increasing the sampling frequency further was not practicable, however).
The extent to which the scale of monitoring would be adequate for detecting effects of the connectivity
treatments on mobile, predatory, arthropods is likely to depend on the species’ life cycle and its unique
patterns of behaviour, coupled with environmental conditions to which it is responding (e.g. availability of prey).
Because of the variability of life cycles and dispersal dynamics among ground beetles (e.g. Holland & Luff
2000; Thomas et al. 2001), designing a study that is scaled appropriately for all species likely to be present
CSG 15 (Rev. 6/02)
20
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
would involve an intensive spatial sampling programme (e.g. Holland et al. 2000; Thomas et al. 2001). For
ground beetles that colonise cropped areas from the field edge, the current study design provided a 14-m
distance into the sprayed area over which the barriers would have prevented dispersal from one connectivity
treatment to another. Further into the sprayed area, mobile species might have been able to move between
the treatments by entering the open (unbarriered) ends of the study plots. If this occurred, it would be expected
to have had a similar influence on catches in the three connectivity treatments, which in the sprayed area
shared the same layout of barriered edges.
A possible criticism of the study design is that arthropod monitoring was carried out only up to 7m into the
sprayed crop area (in order to permit routine crop management operations to continue in the field). The
findings thus do not indicate whether effects of the unsprayed crop edge penetrated to the rest of the sprayed
area. However, suction samples taken 80m from the hedgerow demonstrate clearly that recovery had not
occurred there within the duration of the study, even though other unsprayed edges of the field and the
unsprayed half of the field could in theory have acted as alternative sources of recovery. Furthermore, there
was little evidence for recovery of springtails at 7m into the sprayed area, despite the persistence throughout
the study of high abundance and diversity of springtails and other arthropods monitored at a distance only 10m
away within the unsprayed crop edge.
Effects of the connectivity treatments on ground beetles. Pitfall sampling showed a consistent pattern of
higher catches of the ground beetles Agonum dorsale, Harpalus rufipes and Pterostichus madidus where the
sprayed crop was connected to both the unsprayed edge and hedgerow. For the latter two species this
difference between the connectivity treatments persisted across several sampling occasions. It is notable that
these differences occurred at a relatively small spatial scale of monitoring, given that A. dorsale and P.
madidus are capable of relatively rapid rates of dispersal in arable fields (e.g. Thomas et al. 2002). The
detection of significant treatment effects on such relatively mobile species gives confidence that these ground
beetles were dispersing mainly perpendicular to the field edge rather than into adjacent treatment plots. The
significant differences in ground beetle catches between the treatment contrasts C2 and C1 (which differed
only in hedgerow connectivity) provide evidence that the hedgerow influenced colonisation of the sprayed area
by these ground beetles. However, the hedgerow does not appear to have been the sole source of
colonisation as these ground beetle species were trapped, in lower numbers, in both the treatments that had
no connectivity with the hedgerow (C0 and C1). Isolating the sprayed area from the unsprayed crop edge
made no perceptible difference to the numbers captured in the sprayed area unless the hedgerow was also
isolated. The value of the unsprayed crop edge as a source of colonisation of the sprayed area by these
ground beetle species therefore appears to be influenced strongly by the field boundary against which it is
sited.
The effects of the connectivity treatments on these ground beetles are consistent with their known patterns of
activity and distribution within arable fields. There is evidence that Agonum dorsale exhibits ‘waves’ of spring
dispersal into arable fields from overwintering sites in field boundaries (Coombes & Sotherton 1986; Jensen et
al. 1989). Harpalus rufipes appears to be predominantly associated with field boundaries, where local
aggregations may act as foci for wider distributions in cropped areas (Thomas et al. 2001), although vagility of
H. rufipes appears to be relatively low (Thomas et al. 1997). Pterostichus madidus can occur both at field
edges and also in cropped areas at high activity densities, and large-scale changes in distributions between
adjacent fields have been observed both within and between years (Thomas et al. 2002).
Other species of ground beetle captured in pitfall traps did not exhibit the same pattern of differences between
the connectivity treatments but for these species treatment effects were not statistically significant, principally
as a result of high heterogeneity in trap catches among the four replicate blocks. The pattern of effects
described above for A. dorsale, H. rufipes and P. madidus is typical for the Carabidae as a group and for the
total Coleoptera (Fig. 7).
Effects of the connectivity treatments on springtails and other arthropods. The significant treatment
effects observed for pitfall catches of some beetles (Coleoptera) (see above) give confidence that the study
design is appropriate in scale for monitoring recovery dynamics of springtails, whose rates of recovery
following broad-spectrum organophosphate insecticide applications appear, at least for the most vulnerable
CSG 15 (Rev. 6/02)
21
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
species, to be considerably slower than for macroarthropod groups (e.g. Frampton 2001d). Strictly, the study
design employed here does not distinguish the dispersal component of recovery from other, indirect, effects
such as interaction with predators. In all cases where potential predators of springtails were examined, there
was either no clear difference in predator catches between the connectivity treatments (e.g. as occurred with
spiders), or catches were consistently higher in C2 than the other treatments (as occurred with some ground
beetles). If predation has a strong influence on recovery dynamics, then increased predator catches might be
associated with lower springtail catches. The converse has been demonstrated when predator numbers are
reduced, for example increased abundance of some springtails at the centre of sprayed areas might reflect
reduced predation pressure due to the delayed arrival of recolonising predators (Duffield & Baker 1989;
Duffield & Aebischer 1994). Increased abundance of springtails can also occur when synthetic pyrethroid
insecticides reduce predator abundance (Frampton 1999). In the current study, rather than springtail catches
being lower where predator catches were highest, there was a tendency overall for springtail catches to be
higher in the C2 connectivity treatment than in the other treatments. Abundance of ground beetles was
generally higher in the C2 treatment and there was a significantly higher rate of loss of artificial prey in
treatment C2 on the last sampling date. Possibly, the lack of a clear relationship between springtails, predators
and ‘general’ predation rate as indicated by removal of artificial prey might be explained by: (1) omnivory of the
predators, e.g. Harpalus rufipes is facultatively spermophagous; (2) lack of effects of the connectivity
treatments on spiders, which are numerically important predators of springtails; or (3) the broad-spectrum
effects of chlorpyrifos limiting opportunities for springtail population increases, irrespective of predation
pressure.
For the most abundant springtail groups monitored by suction sampling the pre-insecticide catches were
broadly similar in the unsprayed crop edge and at 7m into the sprayed area but markedly declined in the
sprayed area after the insecticide was applied (Fig. 4). Some individual taxonomic groups exhibited no
evidence of recovery during the study despite high catches being consistently present in the unsprayed edge,
merely 10m away. These results reaffirm the findings from Objectives 1 and 2 (above) that although leaving a
crop edge unsprayed protects arthropods within the edge itself, for the most numerically important groups of
springtails (Lepidocyrtus spp., Isotoma ‘viridis group’), this approach does not assist recovery in the sprayed
area within the same crop season.
As with the pitfall catches of ground beetles, suction catches of arthropods showed significantly higher
abundance in the sprayed area in connectivity treatment C2, i.e. where the unsprayed crop was connected
both to the unsprayed edge and hedgerow, than in the other treatments (C0, C1). This was the case both for
springtails and for non-springtail groups (Fig. 4). Due to spatial variability of the catches, this treatment effect
could not be clearly attributed to any one springtail species, but rather represents an effect of the summed
abundances of several different species. When the accumulated catches for the whole summer were
analysed, however, there was indication that, overall, presence of Orchesella villosa in the sprayed area may
have been influenced by the hedgerow.
Although the majority of arthropods captured by suction sampling were more abundant in the unsprayed crop
edge than the sprayed area after the chlorpyrifos application, there were exceptions. It is notable that
Isotomurus spp. were more abundant in the sprayed area whereas Isotoma ‘viridis group’ (both springtail
family Isotomidae) catches were highest in the unsprayed edge. Within the fungus beetle family Lathridiidae,
Corticariinae were more abundant in the sprayed area whereas Lathridius spp. were more abundant in the
unsprayed edge. There was a tendency, overall, for the small, suction-sampled beetles (Coleoptera) to be
more abundant in the sprayed area, in contrast to the situation with the larger pitfall-sampled ground beetles
which were more abundant in the unsprayed edge. These patterns might reflect a combination of differential
vulnerability to chlorpyrifos as a result of differences in life cycles. Tenerals of Corticariinae were observed in
both the sprayed area and unsprayed edge of the field during July, whereas Lathridius spp. tenerals were only
seen in the unsprayed edge. Newly-emerged adult ground beetles Bembidion obtusum, B. lampros and
Trechus quadristriatus were found in small numbers in the sprayed area, suggesting that for these species and
for the Corticariinae at least part of the population was able to recolonise the sprayed area in situ, their
edaphic larval stages having escaped exposure to chlorpyrifos. For springtails, little is known about their
patterns of exposure, and different life stages (e.g. edaphic vs epigeic) are difficult to determine in the field, so
reasons for the spatial differences between Isotomurus and Isotoma spp. remain unclear.
CSG 15 (Rev. 6/02)
22
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
4. Overall conclusions
Objectives 1, 2 and 3 together provide clear evidence (1) that a 6m-wide unsprayed crop edge can protect
non-target arthropods from adverse effects of individual and repeated insecticide applications; (2) that the
protection of springtails at the crop edge is generally ineffective at assisting the recovery of the most
vulnerable species in the sprayed area; and (3) that the field boundary (in this case a hedgerow) could have
an important influence on the recolonisation of the sprayed area by non-target arthropods. The lack of
springtail recolonisation is of ecological interest because whereas some species susceptible to effects of
chlorpyrifos my be habitat specialists with restricted spatial and/or temporal occurrence (e.g. Entomobrya
nicoleti), others such as Lepidocyrtus and Isotoma spp. are widespread in agricultural land and are evidently
tolerant of other forms of disturbance such as tillage. Lack of recovery among these species appears not to be
related to dispersal, as availability of potential recolonists in the close vicinity apparently is not a limiting factor.
Further studies would be needed to understand the reason(s) for the high vulnerability and poor recovery of
these species.
Acknowledgements
This work was funded by DEFRA. Philip Gould and Eleanor Hendy (Southampton University) assisted with
fieldwork and the identification of arthropods.
References
Alvarez, T., Frampton, G.K. & Goulson, D. (2000). The role of hedgerows in the recolonisation of arable fields
by epigeal Collembola. Pedobiologia 44, 516-526.
Coombes, D.S. & Sotherton, N.W. (1986). The dispersal and distribution of polyphagous predatory Coleoptera
in cereals. Annals of Applied Biology 108, 461-474.
Duffield, S.J. & Baker, S.E. (1989). Spatial and temporal effects of dimethoate use on populations of
Carabidae and their prey in winter wheat. In: Stork, N.E. (ed.) The Role of Ground Beetles in Ecological and
Environmental Studies. Intercept Ltd., Andover. pp. 95-104.
Duffield, S.J. & Aebischer, N.J. (1994). The effect of spatial scale of treatment with dimethoate on invertebrate
population recovery in winter wheat. Journal of Applied Ecology 31, 263-281.
Dunger, W., Schulz, H.-J. & Zimdars, B. (2002). Colonization behaviour of Collembola under different
conditions of dispersal. Pedobiologia 46, 316-327.
Forster, R. & Rothert, H. (1998). The use of field buffer zones as a regulatory measure to reduce the risk to
terrestrial non-target arthropods from pesticide use. Proceedings, 1998 Brighton Crop Protection
Conference – Pests and Diseases. British Crop Protection Council, Farnham. Part 3, pp. 931-938.
Frampton, G.K. (1997). The potential of Collembola as indicators of pesticide usage: evidence and methods from
the UK arable ecosystem. Pedobiologia 41, 179-184.
Frampton, G.K. (1999). Spatial variation in non-target effects of the insecticides chlorpyrifos, cypermethrin and
pirimicarb on Collembola in winter wheat. Pesticide Science 55, 875-886.
Frampton, G.K. (2000a). Recovery responses of soil surface Collembola after spatial and temporal changes in
long-term regimes of pesticide use. Pedobiologia 44, 489-501.
Frampton, G. (2000b). Project PN0934. Interim report on Objective 1: To determine whether use of OP
insecticides has caused local extinction of the collembolan Entomobrya nicoleti in an arable field and its
margins (ADAS Drayton, ‘Field 5’) (project milestone 01/01). Unpublished report. DEFRA / University of
Southampton. 12pp.
Frampton, G.K. (2001a). Large-scale monitoring of non-target pesticide effects on farmland arthropods in
England: The compromise between replication and realism of scale. In: Johnston, J.J. (ed.) Pesticides and
Wildlife. ACS Symposium Series 771. American Chemical Society, Washington DC. pp. 54-67.
Frampton, G. (2001b). Project PN0934. Interim report on Objective 2: To determine whether an unsprayed 6-m
buffer zone protected field margin Collembola from long-term effects of current farm practice pesticide use
in an arable field (ADAS Drayton, ‘Field 5’) (project milestone 02/01). Unpublished report. DEFRA /
University of Southampton. 28pp.
CSG 15 (Rev. 6/02)
23
Project
title
The role of OP insecticides in long-term declines of
Collembola and the importance of buffer zones for recovery
DEFRA
project code
PN0934
Frampton, G. (2001c). Project PN0934. Second interim report on Objective 2: Community-level analysis to
determine whether an unsprayed 6-m buffer zone protected field margin Collembola from long-term effects
of current farm practice pesticide use in an arable field (ADAS Drayton, ‘Field 5’) (project milestone 02/02).
Unpublished report. DEFRA / University of Southampton. 13pp.
Frampton, G. (2001d). The effects of pesticide regimes on non-target arthropods. In: Young, J.E.B., Griffin,
M.J., Alford, D.V. & Ogilvy, S.E. (eds) Reducing agrochemical use on the arable farm. The TALISMAN and
SCARAB projects. DEFRA, London. pp 219-253.
Frampton, G.K. (2002). Long-term impacts of an organophosphate-based regime of pesticides on field and
field-edge Collembola communities. Pest Management Science 58, 991-1001.
Gravesen, E. & Toft, S. (1987). Grass fields as reservoirs for polyphagous predators (Arthropoda) of aphids
(Homopt., Aphididae). Journal of Applied Entomology 104, 461-473.
Holland, J.M. (1998). The effectiveness of exclusion barriers for polyphagous predatory arthropods in wheat.
Bulletin of Entomological Research 88, 305-310.
Holland, J.M. & Luff, M.L. (2000). The effects of agricultural practices on Carabidae in temperate
agroecosystems. Integrated Pest Management Reviews 5, 109-129.
Holland, J.M. Winder, L. & Perry, J.N. (2000). The impact of dimethoate on the spatial distribution of beneficial
arthropods in winter wheat. Annals of Applied Biology 136, 93-105.
Jensen, T.S., Dyring, L., Kristensen, B., Nielsen, B.O. & Rasmussen, E.R. (1989). Spring dispersal and
summer habitat distribution of Agonum dorsale (Coleoptera, Carabidae). Pedobiologia 33, 155-165.
Macleod, A., Wratten, S.D. & Harwood, R.W.J. (1994). The efficiency of a new lightweight suction sampler for
sampling aphids and their predators in arable land. Annals of Applied Biology 124, 11-17.
Mebes, K. H. & Filser, J. (1997). A method for estimating the significance of surface dispersal for population
fluctuations of Collembola in arable land. Pedobiologia 41, 115-122.
Thomas, C.F.G., Green, F. & Marshall, E.J.P. (1997). Distribution, dispersal and population size of the ground
beetles Pterostichus melanarius (Illiger) and Harpalus rufipes (Degeer) (Coleoptera, Carabidae) in field
margin habitats. Biological Agriculture and Horticulture 15, 337-352.
Thomas, C.F.G., Parkinson, L., Griffiths, G.J.K., Frernandez Garcia, A. & Marshall, E.J.P. (2001). Aggregation
and temporal stability of carabid beetle distributions infield and hedgerow habitats. Journal of Applied
Ecology 38, 100-116.
Thomas, C.F.G., Holland, J.M. & Brown, N.J. (2002). The spatial distribution of carabid beetles in agricultural
landscapes. In: Holland, J.M. (ed.) The agroecology of carabid beetles. Intercept Ltd, Andover. pp. 305-344.
van den Brink, P.J. & Ter Braak, C.J.F. (1999). Principal response curves: analysis of time-dependent
multivariate responses of biological community to stress. Environmental Toxicology and Chemistry 18, 138148.
Young, J.E.B., Griffin, M.J., Alford, D.V. & Ogilvy, S.E. (eds) (2001). Reducing agrochemical use on the arable
farm. The TALISMAN and SCARAB projects. DEFRA, London. 416 pp.
CSG 15 (Rev. 6/02)
24