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CABI REF- VM10023
Phase 1 Recommendations
March 2008
Improving the management of leaf miner outbreaks on oil palm in
Ghana
D. Djeddour, G. Masters & F. Wäckers
www.cabi.org
KNOWLEDGE FOR LIFE
Executive Summary
Introduction
The CABI E-UK-Lancaster Environment Centre Alliance in Sustainable Agriculture was
contracted by Unilever to carry out a scoping study at their oil palm plantations in Ghana,
with a view to improving the management of leaf miner outbreaks by a) identifying key
components of current management practices and capturing local knowledge through field
visits and interviews with farmers and managers and b) assessing the potential for alternative
practices and their suitability for incorporation into the system as part of a sustainable
Integrated Pest Management strategy.
A full report summary has been produced and accepted by Unilever. The following is a
synthesis of the key areas for work identified during post-visit meetings and discussions held
between the CABI-Lancaster Alliance and Unilever UK.
Based on existing gaps in
knowledge, work modules for improved IPM implementation are recommended and concept
notes outlining objectives, outputs and suggestions for funding sources are supplied in each
case.
Justification and Recommendations
Pest outbreak patterns in tropical plantations have been studied at length by applied
entomologists. The subtle interplay of interactions between age-structured pest populations,
the predators, pathogens and parasitoids which control them, together with the influences of
external factors such as insecticide use and environmental fluctuations all go to provide an
enormous and complex web of interdependent dynamics for research.
A great deal of raw data was obtained on the brief visit to BOPP (Benso Oil Palm Plantation),
TOPP (Twifo Oil Palm Plantation) and their associated outgrower farms and smallholder
cooperatives. These included leafminer numbers in the field over a number of years, figures
on yield and rainfall patterns across the plantations, as well as comprehensive day to day
practical information on management. The visit was instrumental in highlighting the variety
of growing schemes and conditions under which oil palm is grown in Ghana. The larger,
intensive, monocultural nucleus plantations were reportedly more susceptible to significant
leafminer outbreaks compared to the smallholder cooperatives. Furthermore, the much less
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uniform, small-scale outgrower farms which appeared more species rich and diverse were
reported to have only limited outbreaks. These were characterized by a variety of cover/food
crops and understorey plant species, variable oil palm age structures and were maintained to
differing standards. Similarly, the large differences in topography at BOPP (terraced) and
TOPP (uniform, generally flat or gently undulating landscape) produced dichotomies in
aspects of water management, fertilizer use, microclimate, accessibility for effective chemical
and cultural management even for the large plantations. In addition, progeny trials have been
initiated at BOPP and census data is available for these which could provide vital clues to the
variable susceptibility of different palm cultivars.
Isolating the potential trigger mechanisms for the leafminer complex across such a widely
variable ecological, biophysical and biological agroecosystem was clearly beyond the scope
of this first phase. However a number of research needs have been identified which are key
for sustainable and effective management of the leafminer. These can help build on the
information gathered to allow for the optimization of the IPM management scheme already
practiced and provide a better understanding of the invasion dynamics of the leafminer as well
as promote, and help conserve local biodiversity and control agents, which undoubtedly play a
critical role in the crop system. In addition, information on leafminer outbreaks, and
associated impacts on yield and management practices from plantations at GOPDC (Ghana
Oil Palm Development Company), an integrated agro-industrial company specializing in the
organic cultivation of oil palm in Ghana, would be hugely valuable as a comparator
Recommendations
1.
To enhance understanding of the biology, ecology and systematics of the pest
A fundamental requirement for the management of any pest species, is a broad understanding
of its biology and ecology, together with the biotic (predators, parasitoids, entomopathogens,
viruses) and abiotic (rainfall, temperature, topogratphy etc) factors influencing its population
abundance, dynamics and distribution. Various Coelanomenodera spp. have been reported in
the literature as having outbreaks, with C. lameensis and C. minuta believed to be the
synonymised, outbreaking species and C. elaeidis a non outbreaking species.
The
complicated and confused systematics of this leafminer complex need clarification, through
conventional taxonomic and/or molecular characterization which can then be used to inform
field managers and workers enabling the correct identification of the problem species
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involved. The pest ecology, particularly the population dynamics, also needs further detailed
assessment. Previous work needs to be confirmed and built on. Mariau and Lecoustre (2004)
identified a range of biotic mortality factors for C. lameensis in West Africa for example.
Further assessments of the augmentation potential of these together with investigations of the
factors constraining the impact these natural enemies (predators and parasitoids) have on
populations are needed.
2.
To maximize conservation biological control and enhance the effect of under storey
A greatly improved leafminer monitoring system had been implemented and spray thresholds
were respected on the plantations visited.
However, without doubt, communities of
indigenous natural enemies (predators and parasitoids) are disrupted by non selective
insecticides. If populations were allowed to grow and develop a natural dynamic, then , these
natural enemies will play an important part in maintaining leafminer numbers below
economically damaging levels. This balance was clearly better achieved on the smallholder
and outgrower farms but the extent to which they control the leafminer and how this can be
further enhanced by cover crops and epiphytes, needs further research in order to optimize the
control timing and reaction of monitoring teams.
Targeted strategies should be developed that enhance key biological control agents through
the promotion of non-crop vegetation (cover crops in under storey, epiphytes) that provide
insect predators and parasitoids with (extra) floral nectar and alternative prey.
3.
To assess the potential for resistance breeding
Maximum yield progeny trials and work on mother plants is currently underway and have
associated census data. However, no indication or analysis has been carried out with regard to
the susceptibility of cultivars to the leafminer. These data could be collected as part of the
existing trial and included for analysis in the overall review and digitization of all available
hard data. Plant resistance mechanisms are commonly inducible by a range of elicitors. As
part of the susceptibility screening it could be investigated whether leaf miner damage can be
further reduced through resistance induction.
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4.
To assess the biodiversity supported by the different systems
In order to identify any potential drivers and patterns to leafminer outbreaks, a greater
understanding of the surrounding biodiversity within the habitat is needed across the different
growing systems. It is now understood that biodiversity, in terms of what species are present,
in what functional groups and in what abundance, is fundamental in determining how an
ecosystem is structured and functions.
Habitat biodiversity is a fundamental tenant of
ecosystem resistance and resilience to change.
This recommendation examines which
growing system- plantation, outgrower, smallholder or organic- has the greatest biodiversity
and how this compares with native/natural systems. The West African remnant tropical forest
(now largely protected) provides a baseline for comparing the oil palm production systems
against.
Additionally, Ben Phalan (Cambridge University) is conducting a biodiversity
assessment of TOPP and the work recommended here will provide valuable information on
how important (or not) in terms of conservation, the different growing systems are.
5.
To investigate the potential for more rational and environmentally benign
insecticide use
A fundamental subset of any IPM strategy must, where integration of pesticides is still a
prerequisite, combine the use of selective, non-toxic products with optimised, minimised but
efficacious intervention, based on accurate monitoring and diagnosis of the pest. In addition,
minimisation of risks, costs and contamination can be achieved through considered
application techniques. In BOPP and TOPP, the usual method of control for the leafminer was
by thermal fogging with Evisect S (Thiocyclam hydrogen oxalate) once numbers of
leafminers reached the predetermined action threshold. Whilst it can be effective, fogging is
subject to drift, uneven coverage and consistency will depend on prevailing environmental
conditions. Evisect S is an expensive compound used primarily on the plantations, whose
active ingredient has actually been withdrawn from the EC market list. It is effective only on
the adult stages, leaving the damage causing larvae unaffected, and has an adverse effect on a
number of beneficial non-target insects, including the ant species which prey on C. lameensis.
There is therefore a need to evaluate alternative chemicals which are toxicologically and
environmentally safe as well as review application techniques to include more targeted
approaches such as those afforded by trunk injection of systemics, for example. This is a
preferred method against phytophagous insects in the Far East and if correctly implemented,
could potentially be organised to cover large areas in BOPP and TOPP, without too much
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specialist capital expenditure and would target the developmental stages of the leafminer.
Concerns surrounding deleterious effects on the palms could be investigated in trials and non
phytotoxic formulations selected. Trials with Confidor® OD 200 (imidacloprid) and Proteus®
OD 110 (thiacloprid and deltamethrin) carried out for Unilever (Yawson and Appiah, OPRI
technical report, 2006) recommended further studies be made into trunk injection and soil
drenching techniques as their results proved inconclusive.
Note- It was evident during the field visit that digitisation of the census monitoring system
would not only enhance the recording accuracy and create a less labour intensive activity
through the elimination of multiple handling but would also be of benefit for any subsequent
analysis, trend detection and historical record. Huge backlogs of hard data are available as
daily and monthly summary sheets for all BOPP and TOPP plantations and smallholdings as
well as progeny trials and more recent data is already available electronically.
Recommendations to use hand held PDA systems to electronically record leaf miners in the
field and upload information directly into a database have already been acted upon by
Unilever.
To address these recommendations we propose a series of individual but linkable
medium/long term projects. These are outlined in the concept notes which follow. A series of
shorter term research activities are also detailed focusing on key component activities within
each concept note.
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Concept Notes
1.
To improve the knowledge of the biology, ecology and systematics of
Coelaenomenodora lameensis in oil palm (See recommendation 1 (and 4)).
Objectives
 To detail the ecological relationships between the leaf miner and the host plant.
 To determine the importance of factors such as drought and the predator/parasitoid
complexes in determining the dynamics of the leafminer.
 To establish the systematics of the oil palm leafminer
Brief Description
Although there is a history of looking at the autecology of the oil palm leaf miner, the ecology
of this pest, particularly the drivers of its dynamics, its population limits, its impact on plant
growth, the relationship of pest incidence to damage, and the effect of both this and of
graduated leaf loss on subsequent oil palm crops and fecundity are not known. In addition, the
systematics of this pest are not understood and there is confusion in the literature over the
identity of the outbreaking leaf mining species vs. a non-outbreaking related species.
Knowledge gathered would allow further investigations into the potential for augmentation of
natural enemies through mass rearing and identification of potential biopesticide agents
(entomopathogens) for use under an organic system.
Project Activities
1. Taxonomic and molecular characterization of the oil palm leaf miner complex leading
to, if appropriate, the production of simple field identification guides to aid field
workers and managers.
2. Assessment through monitoring, modeling and experimentation of the role of abiotic
drivers, particularly drought, in the abundance, dynamics and spatial distribution of
the leaf miner. Investigate the potential influences, if any, of localised,
topographically-induced microclimates within plantations as outbreak initiation foci.
3. Characterisation and assessment (as above) of the importance of the natural enemy
complex of the leaf miner to its abundance, distribution and dynamics. Comparative
analysis of these complexes and leafminer outbreak history across the oil palm
growing schemes (plantation, smallholdings, farms and organic).
4. Historical assessment of the impact on yield and economic potential of oil palms
relative to leafminer loads.
Duration and Estimated Total Cost
Two, 3 year PhD projects or 1 Postdoc and 1 PhD project…………………………..£300, 000
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Partners/collaborators/sponsors required
Partners: CABI and Lancaster University, Cambridge University, Cape Coast University or
University of Ghana, Oil Palm Research Institute, Industry Partner, Real IPM company.
Funders: NERC (Case), BBSRC, Royal Society Networking Scheme.
Short Term Activities
To improve the knowledge of the biology, ecology
Coelaenomendora lameensis in oil palm
and
systematics
of
Objectives
Assessment through monitoring, data analysis and modeling of the role of abiotic and
biotic drivers, particularly drought and ants on the abundance, dynamics and spatial
distribution of the leaf miner
Activities
1. Digitize all available census and rainfall data from BOPP, TOPP
2. Include ant presence/absence in future census taking
3. Use historical and current census data from BOPP, TOPP to assess and analyse the
influence of rainfall patterns in determining the dynamics of the leafminer populations;
use modeling tools to help identify trends and triggers, predict potential outbreaks and use
the information to feedback into the management protocols with a view to more rationally
timed and judicious control.
Duration
1 year (Postdoc)
Partners: CABI and Lancaster University, Cape Coast University or University of Ghana,
Oil Palm Research Institute, Unilever.
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2. To maximize conservation biological control of Coelaenomenodora lameensis in oil
palm and enhance the effect of under storey
See recommendations 2 and 3
Objective
To enhance the numbers and impact of leaf miner natural enemies through targeted use of
non-crop vegetation (legumes in under storey).
Brief description
Mariau and Lecoustre (2004) identified a range of biotic mortality factors for C. lameensis in
West Africa. Among these, ants were found to play a dominant role in regulating leaf miner
populations by cutting open the mines and destroying the larvae.
Besides ants, egg-, larval-, and pupal-parasitoid species were found to be the main additional
mortality factor (Mariau and Lecoustre, 2004).
In addition to attacking leafminers, ants and parasitoids are obligatory nectar consumers,
requiring carbohydrates as a complement to the consumption of prey (ants), or as the only
food source (adult parasitoids). Recently, awareness has grown among biological control
workers that the absence of nectar resources in agriculture imposes a serious constraint on the
effectiveness of natural enemies (Bugg et al., 1991; Gurr et al., 2005; Wäckers et al., 2007).
The common use of Legume Cover Plants (LCP) in oil palm production could provide an
excellent opportunity to provide nectar in support of leaf miner antagonists. The benefits of
understorey in maintaining populations of natural enemies is well known and has worked well
in oil palm systems in other parts of the world such as SE Asia for bagworm control. Legumes
can be especially suited for this purpose as many legumes feature extrafloral nectaries,
providing nectar over prolonged periods. As the currently used Pueraria phaseoloides
(tropical kudzu) does not provide extrafloral nectar, replacing it with a nectar producing
legume.
Project activities
1. Assessment of the current non-crop vegetation and associated biological control
agents at different plantations/farms/organic plantations.
2. Correlate this functional biodiversity with levels of natural pest control.
3. Identify candidate legume cover crops based on their resource provision (extra-floral
nectar and alternative prey) for biological control agents, in addition to the criteria of
nitrogen fixation and weed suppression.
4. Compare most promising legume cover crops with regard to the predator and
parasitoid fauna they support and assess impact on leaf miner levels.
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Duration and Estimated Total Cost
2-year Postdoc or 3-year PhD……………………………………………………. £150, 000
Partners/collaborators/sponsors required
Partners: CABI & Lancaster University, University of Ghana, Industry Partners.
Sponsors: Link BBSRC, NERC if combined with biodiversity assessments focused on
conservation, Funding sources in support of sustainable palm oil production, Biofuel funding?
Table 1: LCP species commonly used in oil palm include:
Legume cover crop species
Centrosema pubescens
Pueraria phaseoloides
Comments
(suitable for marine clays)
(often
mixed
with
Calopogonium)
Calopogonium mucunoides
(not very drought tolerant,
used for quick ground cover
establishment)
(shade tolerant, often mixed
with Pueraria and persists
when canopy closes)
Calapogoinum caeruleum
Phosphocarpus spp
Vigna spp.
Phaseolus spp.
Additional income as food
crop.
Additional income as food
crop.
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Extrafloral nectar
NO
NO
However, Extrafloral nectaries have
been described for the genus Pueraria
(Zimmermann 1932)
Extrafloral nectaries have been
described for the genus Calopogonium
(Díaz-Castelazo et al. 2004)
NO
NO
Extrafloral nectaries are widespread in
the genus Vigna
Extrafloral nectaries are widespread in
the genus Phaseolus
Short Term Activities
To maximize conservation biological control of Coelaenomenodora lameensis in oil
palm through the use of selected under storey plants
Objective
To scope the potential to use selected cover crops and/or sugar sprays to enhance the
numbers and impact of leaf miner natural enemies and/or deter leaf miners.
Activities
1. Establish experimental plots to study the effect of cover crop & nectar on ants and leaf
miners. Use a factorial design varying the factors cover crop and nectar availability.
Understorey vegetation
Nectar availability
No cover crop
-
-
Legume with EFN
+
+
Legume without EFN
+
-
Sugar spray
-
+
2. Study the potential of using cover crop species with aromatic oils as a leaf miner leaf
miner repellent by comparing cover crops with high/low aromatic oil content, as well as
undamaged versus damaged cover crop.
Duration: 1 year (Postdoc)
Partners: Lancaster University & CABI, University of Ghana, Unilever.
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3. To assess the potential for resistance breeding in oil palm
See recommendation 3
Objective
To investigate variation in constitutive or induced resistance between oil palm cultivars to
scope the potential of using pest resistance as part of leafminer IPM.
Brief description
Plants have developed a broad range of morphological and chemical adaptations to limit the
negative impact of herbivory. Many plant secondary chemicals have been shown to repel
herbivores or decrease herbivore survival or performance, thus contributing to plant’s
resistance. Resistance can be constitutive, i.e. preformed without being affected by biotic or
abiotic stresses. However, many plants raise their resistance levels in response to herbivory,
so-called “induced resistance”. Recent studies have shown that nutrient levels and drought can
further affect resistance expression. Cultivars often vary considerably with regard to their
constitutive and induced levels of resistance. To understand the potential contribution of plant
resistance as part of oil palm IPM, the dynamics of resistance have to be addressed.
The currently run progeny trials provide a unique opportunity to assess the resistance of
available cultivars. In a second phase, the dynamics of available resistance traits could be
addressed in more detail.
Expected output
Phase I
1. Overview over the range of leafminer resistance among cultivars currently tested within
progeny trials.
Phase II
2. Investigate the potential to further raise resistance levels through resistance induction.
3. Interactions between pest resistance and abiotic factors (fertilizer use, drought)
Project activities
Phase I
Collate and analyse exisiting data collection for correlation between cultivar and leafminer
impact/outbreaks. Collect further data as part of the existing census and include this as part of
the overall cultivar assessment.
Phase II
Investigate the potential to further raise resistance levels through resistance induction, a
selection of cultivars showing low susceptibility in the progeny trial could be treated with a
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plant hormone, known to elicit induced resistance. Induced and untreated individuals can
subsequently be monitored for levels of leaf miner infestation.
Interactions between (induced) resistance and abiotic stress factors can be tested using
selected cultivars in fertilizer/irrigation trials.
Recommend cultivars for future planting based on a cost-benefit analysis of leafminer
resistance and productive capability
Duration/timescale Estimated Total Cost
Phase I could be done as an add-on to the ongoing cultivar assessment and should provide
results within 1 year……………………………………………………….. £40, 000
Phase II Based on the outcome of the initial resistance assessment, this could be followed up
with a second phase project consisting of a two-year postdoc…………….£150, 000
Partners/collaborators/sponsors required
Partners: CABI & Lancaster University, University of Ghana, Oil Palm Breeders (CIRAD),
Industry Partners.
Sponsors: Link BBSRC, Funding sources in support of sustainable palm oil production,
Biofuel funding?
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Short term activities
Assess the potential for resistance breeding in oil palm
Objective
To investigate variation in constitutive or induced resistance between oil palm cultivars to
scope the potential of using selective breeding for pest resistance as part of leafminer IPM
Activities
1. Collate and analyse exisiting census data to identify any correlation between cultivar
and leafminer impact/outbreaks.
2. Use established progeny trials to obtain overview over the variability among currently
tested cultivars with regard to leafminer resistance
3. Conduct bioassays to assess the mechanism underlying resistance
Duration: 1 year (Postdoc)
Partners: Lancaster University & CABI, University of Ghana, Oil Palm Breeders
(CIRAD), Unilever.
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4. To assess habitat biodiversity in the different oil palm plantation systems with
relevance to leafminer pests
See recommendation 4
Objective
To determine the contribution of oil palm production to biodiversity conservation when
compared across different production systems and with native habitat.
Brief description
It is apparent that biodiversity, the number and identity of species within an ecosystem or
habitat, is an important driver in many ecosystem processes, particularly service provision
such as water regulation, water quality, ecosystem resistance and resilience to extreme biotic
and abiotic events and the provision of natural enemies to pests. Different agricultural
production systems affect the number of species within the system. Building on work already
being conducted at TOPP (Ben Phalan), the role of plantations, smallholdings, outgrowers
and organic systems in determining habitat biodiversity needs to be investigated.
Additionally, there is a topographical difference between TOPP and BOPP, such differences
in landscape can generate differences in biodiversity, and so the two estates need to be
compared.
Project Activity
Surveys of different production systems for species identity (where possible), species relative
abundance and other measures of botanical and faunistic diversity.
Duration and Estimated Total Cost
One 3 year PhD project………………………………………………………………£150, 000
Partners/collaborators/sponsors required
Partner: CABI and Lancaster
University/University of Ghana.
University,
Imperial
College
Sponsors: NERC (CASE), Royal Society Networking Scheme., WWF?
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and
Cape
Coast
5. To investigate the potential for more rational and environmentally benign
insecticide use
See recommendation 5
Objective
To investigate alternative application techniques and pesticides in order to rationalise
chemical use and delivery and achieve more selective, environmentally benign control of
leaminers in oil palm.
Brief Description
There is a need to evaluate alternative conventional, readily accessible pesticides which could
form elements of a sustainable IPM strategy for leafminer control. The current chemical of
choice (Evisect S) and its mode of application (hot fogging) not only has a negative impact on
beneficial fauna and the wider environment but is also limited by the life stage targeted
(adults only). Trunk injection of systemic pesticides has been used in large-scale campaigns in
the Far East providing a more selective and environmentally-sound technique, carrying the
chemical to all fronds, and eliminating risk of side-effects, including toxicological problems.
Trials are needed to examine a range of insecticides, techniques and application rates to
optimise and rationalise chemical use within the IPM framework.
Project Activities
1.
Search for alternative new systemic chemicals from Ghana’s approved list and if
appropriate beyond, to identify candidates with high selectivity, low toxicology, and
those which are easily available and affordable.
2.
Undertake trials using the above on designated palm plots with various application
techniques (e.g. soil drench, trunk and root injection) and carry out bioassays to
identify optimal dosage for cost effectiveness against the various life stages.
3.
Assess the phytotoxic effect (if any) of the various formulations and investigate the
practicalities and benefits of incorporating trace elements in the treatment.
Duration and Estimated Total Cost
One year (Post Doc)………………………………………………………………£ TBC
Partners/collaborators/sponsors required
Partner: Lancaster University, Imperial College and Cape Coast University/University of
Ghana, Bayer, Syngenta International, PIP (Pesticides Initiative Programme), PPRSD (The
Plant Protection and Regulatory Services Directorate)
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Acknowledgements
We would like to extend our thanks and gratitude to all the members of the Unilever Ghana
team. Particular thanks go to Neneyo Mate-Kole, Emmanuel Ahiable and Samuel Avaala
who made us very welcome and to whom no request was too much trouble. Additionally,
thanks to our drivers, Francis and Anthony for looking after us and ensuring a smooth
transition between sites.
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