Download control of aphid vector spread of lily symptomless virus and lily

Control of Aphid Vector Spread of Lily Symptomless Virus and Lily
Mottle Virus by Mineral Oil/Insecticide Sprays in Lilium
C.J. Asjes and G.J. Blom-Barnhoorn
Bulb Research Centre
P.O. Box 85
2160 AB Lisse
The Netherlands
Keywords: lily symptomless virus, lily mottle virus, mineral oil, deltamethrin, acephate,
pymetrozine, virus spread.
Abstract
The inhibitory effect of mineral oil, synthetic pyrethroid insecticide,
organophosphorus insecticide and a pyridine azomethine insecticide on the spread of
aphid-borne non-persistently transmitted lily symptomless virus (LSV; carlavirus)
and lily mottle virus (LMoV; potyvirus) in Lilium was studied. The control effect of
spray mixtures of mineral oil (‘Luxan oil H’) and pyrethroid insecticide deltamethrin
(‘Decis’) serially reported about in the past was confirmed. The organophosphorus
insecticide acephate (‘Ypsilon’) and the pyridine azomethine insecticide pymetrozine
(‘Plenum’) applied as single sprays were about half as effective as deltamethrin in the
control of virus spread. The effect of acephate and pymetrozine in mixed sprays with
mineral oil proved to be similar in control efficacy as sprays of mineral oil plus
pyrethroid. The impact of this newly found effect and mode of action of the systemic
insecticides as additive to mineral-oil sprays is discussed.
INTRODUCTION
The control of viruses in Lilium in the Netherlands is mainly concerned with the
prevention of spread of non-persistently aphid-transmitted viruses such as lily
symptomless virus (LSV; carlavirus) and lily mottle virus (LMoV; potyvirus; known up
till 1990s as tulip breaking virus (TBV); Dekker et al., 1993; Derks et al., 1994). Bradley
et al. (1962) reported the inhibition of spread of aphid-borne non-persistently transmitted
plant viruses by oil to cover the leaf surfaces. Mineral oils have been used in lilies in the
Netherlands since the mid 1960s (Asjes, 1976). The synthetic pyrethroid insecticides,
which are effective against both acquisition and inoculation in virus transmission, were
introduced in the early 1980s (Asjes, 1981; Gibson et al., 1982; Rice et al., 1983). The
addition of synthetic pyrethroids to oil allowed the volume of oil to be halved without loss
of efficacy. This practice has been used since the early 1990s (Asjes, 1989; 1991; Asjes
and Blom-Barnhoorn, 1994; Asjes and Blom-Barnhoorn, 2000). Sprays are applied
weekly in May-July to control rapid spread, and fortnightly in August-September to
control the slower spread. They are applied at a pressure of 400 kPa in 400 L of water per
hectare. In this paper data on the efficacy of mineral-oil sprays with other insecticides
than those of the synthetic pyrethroids will be presented.
MATERIAL AND METHODS
Plant Material
Virus-tested lily bulbs (9-10 cm circumference; 100/plot) of cv. Vivaldi (Asiatic
hybrid) were used. ‘Vivaldi’ flowered in the 1st week of July and showed senescence in
late September. Plots in three randomised blocks were planted in late March. Each plot
had two pairs of five rows (18 cm between rows) of virus-tested lilies separated by one
row of LSV+LMoV-infected bulbs of cv. Enchantment (Asiatic hybrid). The trial beds (1
m wide) with the plots were flanked by paths (50 cm) and intermediate beds (1 m) sown
with grass. Dahlias were planted (1 m) between the plots.
Proc. 8th Int. Symp. on Flowerbulbs
Eds. G. Littlejohn et al.
Acta Hort. 570, ISHS 2002
277
Chemicals
The mineral-oil brand used was Luxan oil H (93 % oil; Asjes and BlomBarnhoorn, 2000) furtherly referred to as ‘Luxan’. The synthetic pyrethroid insecticide
was deltamethrin in ‘Decis’ (2.5 % a.i.; 0.0025 % (w/v); 10 g/ha = 400 ml commercial
product). The organophosphorus insecticide was acephate in ‘Ypsilon’ (80 % a.i.; 1 kg/ha
of commercial product). The pyridine azomethine insecticide was pymetrozine in
‘Plenum’ (25WP; 100 g a.i./ha; 0.4 kg/ha of commercial product). In 1998 ‘Plenum’ was
added to the sprays of ‘Decis’ at July 7 and 21, and August 4 and 18 (treatment 4 in Table
2). In 1998 ‘Decis’ was replaced by ‘Plenum’ (treatment 9 in Table 2) at the same dates.
In 1999 the same was done at June 29 and July 13 and 27 in the ‘3x-treatments’
(treatment 5 and 8 in Table 2) and additionally at August 10 in the ‘4x-treatments’
(treatment 9 in Table 2). Brand names will be used in Tables 1 and 2. ‘Ypsilon’ was
kindly supplied by Luxan BV at Elst and ‘Plenum’ by Novartis Agro Benelux BV at
Roosendaal.
Application of Sprays
Emulsions were prepared shortly before use and then applied with a knapsack
sprayer (Birchmeijer Helico nozzles 1.2) at a pressure of 400 kPa and at a volume
equivalent to 400 L/ha. Spraying was carried out in calm weather to minimise spray drift.
The equivalent dosages were 3.1 (0.78 %) and 6.25 L/ha (1.56 %) for Luxan oil H, 400
mL/ha of Decis, 1 Kg and ½ Kg/ha of Ypsilon and 0.4 Kg/ha of Plenum. In the Tables
half volumes and weights will only be mentioned separately. Sprays were applied weekly
in May-July and fortnightly in August-September.
Assessment of Bulb Weight and Virus Infection
The bulbs harvested in October were stored at 0°C till January-February. They
were then washed and dried overnight. The mean weight ratios were calculated as weight
of n-treated bulbs: weight of n-control bulbs x 100. The presence of LSV and LMoV in
each bulb of Vivaldi was assessed by DSA-ELISA (van Schadewijk, 1986). The rates of
infection were calculated for separately infected plants for LSV, LMoV or both. The
percentage of spread reduction was calculated by 100 – (rate of virus infection of treated
plots : rate of virus infection in untreated plots x 100).
RESULTS
Table 1 shows weight ratios, percentages of virus infection and reduction of virus
spread by mineral oil and the insecticides deltamethrin and acephate.
In 1997 and 1998 weight ratios were not significantly different from the data
obtained in the untreated plots, except treatment 4 in 1998. In 1999 the infestation by
Botrytis troubled weight ratios too strongly to indicate a possible yield-reductive effect of
mineral-oil/insecticide sprays. The control by acephate in Ypsilon was less effective than
by deltamethrin in Decis, viz., 20-33 % and 41-51 % reduction of virus spread,
respectively. The level of efficacy of sprays of Luxan oil H plus deltamethrin was similar
to that obtained by Luxan oil H plus acephate. Sprays of Luxan oil H (3.1 l/ha) plus
acephate (1/2 kg/ha) were least effective (treatment 9).
Table 2 shows data on weight ratios, percentages of virus infection and reduction
of virus spread by mineral oil and the insecticides deltamethrin and pymetrozine.
The control by single sprays of Plenum was about half or less effective than that
obtained by Decis. The control by mixed sprays of Luxan oil H plus Decis or Plenum was
similarly effective.
DISCUSSION
Current-season infection by LSV and LMoV of lily cv. Vivaldi did not evidently
affect bulb yields while primary infection of both viruses is traceable from July onwards
(Asjes et al., 2000). The potential reduction of bulb yields may also be due to spray
treatments, for instance by mineral oils (Asjes, 1984). The potential infestation by
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Botrytis near the end of the field season additionally affects bulb yields as became
evident in 1999 when fungicide sprays generally sufficiently effective proved
unsatisfactory. The erratic infestation by the fungus may have affected virus spread only
slightly or rather not at all, as the greater part (85-90 %) of spread per season occurs in
May-July (Asjes et al., 1996; Asjes, 1997; 2000).
The insecticides applied in single sprays were differently effective in the
prevention of virus spread. The pyrethroid deltamethrin confirmed its efficacy as single
spray (Asjes, 1981; 1997). Pymetrozine and acephate were less but still effective under
conditions of high virus infection potential. These data confirmed earlier results on
control by systemically active compounds such as imidacloprid (Asjes et al., 1996) and
aldicarb (Asjes, 1991).
The mode of action of systemic compounds in spread of non-persistently
transmitted viruses is only partially understandable. Pymetrozine interferes with the
feeding of aphids while walking mobility is not affected (Kayser et al., 1994; Fuog et al.,
1996). The aphids are not knocked down on contact but seem to die of starvation
(Harrewijn and Kayser, 1997). The compound does not have a deterrent or antifeedant
action. Pymetrozine does not effectively inhibit virus acquisition, but it reduces
subsequent inoculation of healthy plants (Harrewijn and Piron, 1994). The effect of
pyrethroid insecticide to reduce virus transmission by early flight removal from treated
plants (Gibson et al., 1982; Rice et al., 1983) did not become additionally evident in
mixed sprays of deltamethrin and pymetrozine in 1998 (Table 2: 4 and 5). Possibly the
effect of other systemically active compounds may similarly be due to reduction of
inoculation rather than acquisition. However, data in literature to substantiate this
assumption were not found so far.
The level of control efficacy by pymetrozine and acephate as additive to ‘Luxan
oil H’ was practically similar to that attained by sprays of this brand plus deltamethrin.
The addition of imidacloprid to mineral-oil sprays yielded a similar result in a one-year
trial (unpublished results; 1998).
The newly found effect of other insecticides than synthetic pyrethroids to prevent
spread of non-persistently transmitted viruses in lily may also control occasional resident
aphids in some cultivars, for instance in Oriental hybrids. This is particularly worthwhile
for the control of Aphis gossypii, which species became more prominent in last decades
(Asjes, 1997). Pymetrozine was effective in the control of this species (Kayser et al.,
1994). The build-up of possible resistance to systemically active insecticides may be
controllable by alternative use of pyrethroids and these compounds. The effect of reduced
dosages of acephate and pymetrozine and the long-term efficacy less frequently applied
than weekly must be furtherly investigated.
Literature Cited
Asjes, C.J. 1976. Some developments of the virus pathology in lilies in the Netherlands.
In: Lily Yearbook North American Lily Society 29:120-126.
Asjes, C.J. 1981. Control of stylet-borne virus spread by aphids of tulip breaking virus in
lilies and tulip, and hyacinth mosaic virus in hyacinth by pirimicarb and permethrin
sprays versus mineral-oil sorays. Mededelingen Faculteit Landbouw Wetenschappen
Rijksuniversiteit, Gent, 46/3:1073-1077.
Asjes, C.J. 1984. Control of field spread of tulip breaking virus in Lilium cv. Enchantment
by different brands of mineral oil. Crop Protection 3:111-124.
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Asjes, C.J. 1997. Virus in bloembollen in kaart gebracht. Bloembollencultuur 108 (4):150.
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virus and lily mottle virus in Lilium in the Netherlands. Virus Research: in press.
Asjes, C.J. and Blom-Barnhoorn, G.J. 1994. Air-borne field spread of tulip breaking
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pheromone in the Netherlands. Acta Hort. 377:301-310.
Asjes, C.J. and Blom-Barnhoorn, G.J. 2000. Use of mineral spray oils and pyrethroid
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virus in Lilium (Liliales: Liliaceae). Proceedings International Conference on Sprays
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Asjes, C.J., Blom-Barnhoorn, G.J. and Schadewijk, A.R. van. 2000. Effect of seasonal
detection of lily symptomless virus and lily mottle virus on aphid-borne virus spread
in Lilium in the Netherlands. Proceedings Xth Symposium on Virus Diseases of
Ornamental Plants, USA (May 2000). Acta Hort.: in press.
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Lilium in the Netherlands. Acta Hort. 432:290-297.
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inhibited by oils. Virology 18:327-328.
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S.A. 1993. Characterization of potyviruses from tulip and lily which cause flowerbreaking. Journal General Virology 74:881-887.
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280
Tables
Table 1. Effect of mineral oil and insecticides on the spread of lily symptomless virus
(LSV) and lily mottle virus (LMoV) in lily cv. Vivaldi in 1997-1999.
Treatment
Weight ratio *)
1997 1998 1999
1. Untreated
100
2. Decis
100
3. Ypsilon
100
4. Luxan + Decis
92
5. Luxan + Ypsilon
99
6. Luxan+Ypsilon (½ kg)
7. Luxan(3.1 l)+Decis
8. Luxan(3.1 l)+Ypsilon
9. Luxan(3.1 l)+Ypsilon(½ kg) -
100
95
101
108
105
-
100
96
92
91
89
94
99
81
95
% LSV+LMoV
1997 1998 1999
% spread reduction
1997 1998 1999
56.1
28.6
37.6
7.2
5.0
-
0
49
33
87
91
-
79.1
47.0
63.1
10.6
16.7
-
68.9
33.8
52.1
8.7
6.3
9.4
11.4
13.2
24.5
0
41
20
87
79
-
0
51
24
87
91
86
83
81
64
*) In 1999 bulb weights were variably affected by non-uniform incidence of Botrytis elliptica leaf
infection near the end of the field season.
Table 2. Effect of mineral oil and insecticides on the spread of lily symptomless virus
(LSV) and lily mottle virus (LMoV) in lily cv. Vivaldi in 1998-1999.
Treatment
1. Untreated
2. Decis
3. Plenum
4. Decis/Plenum (4x)
5. Decis/Plenum (3x)
6. Luxan+Decis
7. Luxan+Plenum
8. Luxan+Decis/Plenum (3x)
9. Luxan+Decis/Plenum (4x)
Weight ratio *)
1998
1999
100
95
100
103
108
109
109
100
96
98
91
95
95
87
% LSV+LMoV
1998
1999
79.1
47.1
64.1
45.6
10.6
12.5
11.4
68.9
33.8
43.8
8.7
9.3
6.0
9.4
% spread reduction
1998 1999
0
41
19
42
87
84
86
0
51
36
87
87
91
86
*) Bulb weights were variably affected by the non-uniform incidence of Botrytis infection near
the end of the field season in 1999.
281