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On the final day of the workshop the participants split into several working groups in order to discuss and clarify the recommendations that would be the result of the meeting. These would represent a synopsis of the views of the participants and as such would act as the basis on which any subsequent release of Teretriosoma nigrescens would be made.
The working groups covered the following areas:
- General statement recommending the release of T. nigrescens into Africa.
- Release and monitoring methodology.
- Further research and training requirements.
- Donor awareness
1. Subject: General recommendation for the introduction of Teretriosoma nigrescens as a beneficial insect into Africa.
With regard to the meeting held at Cotonou in June 1989 that proposed T. nigrescens as a potential bio-control agent for the Larger Grain Borer and with respect to the results of the tests undertaken as a result of that meeting:
- that T. nigrescens does not breed on vegetation or on plant products
- that T. nigrescens poses no threat to beneficial insects in particular bees and silkworms
- that T. nigrescens shows a strong prey specificity
The workshop of the 5-6 November 1990 held in Lomé, Togo recommends the release of T. nigrescens into Africa.
2. Subject: introduction of T. nigrescens into Africa: recommendations for release sad monitoring to assess its impact.
A) A full quantitative assessment of the release of T. nigrescens, in particular its behaviour on release, its impact on populations of LGB and a comprehensive documentation of the entire programme is of vital importance to guide the further development of pest management strategies against LGB.
B) Number of release points: in the initial phase the number of release points should depend on available monitoring capacity.
C) Release of the predator should be undertaken in two phases; an initial phase to see if the insect can establish itself and, depending on the results of this, a general release throughout the country in question.
D) For the initial release one village should be selected from each agro-climatic zone, where possible, to take account of various storage and climatic factors.
E) introduction methodology should be decided upon after consultation with national and/or international organisations with experience in this field.
F) Selection of release sites: villages chosen for the release of T. nigrescens should contain a good number of stores infested with LGB. Five to ten stores should be selected in each village as release points. Adequate arrangements would have to be made with farmers so that the selected stores can be sampled during the course of the storage season.
G) Time of release: the predator should be released at an appropriate time in the infestation cycle of LGB. This will depend on the country or region. Predators should be released when LGB is present.
H) Monitoring dispersal of T. nigrescens to assess spread of the predator between stores within the village:
- At regular intervals cobs from stores in the release village should be examined for presence of the predator.
- Number of cobs and stores to be examined depends on the resources available but this should be as many as possible.
- Pheromone-baited traps should not be used as they may interfere with the dispersal process.
Dispersal of T. nigrescens to surrounding areas will be assessed every two months after liberation of the predator. Funnel shaped flight traps, baited with synthetic LGB aggregation pheromone will be equally spaced, at a distance apart of 1 km, in a ring of radius 1 km. around the selected village. Traps should be hung 2 m above the ground and left in place overnight to ensure the attraction of insects only from the immediate surroundings.
Following the first capture of T. nigrescens at 1 km, dispersal beyond this distance can be monitored by placing traps in neighbouring villages etc. in the directions in which the predator appears to be spreading. Stores in such villages could be inspected for the predator once it is detected in nearby flight-traps.
I) To assess impact of T. nigrescens on reduction of storage losses at each release village:
- Sequential sampling of cobs should be undertaken from selected stores.
- The numbers of stores selected and number of cobs extracted will have to depend on manpower and resource availability.
- information on grain removal/consumption should be collected from the owner of each store, in order to calculate real weight loss of grain stored over a season.
- Sampling should start before release and at regular intervals afterwards.
- Previous data, where available should be brought together.
3. Subject: Further research and training needs.
In view of the ecological complexities of maize-based farming systems involving maize and cassava storage (including wooden structures), maize fields of different varieties and maturity and other hosts (e.g. cassava and sorghum) and the natural vegetation as modified by weather and climate, both in the areas of origin of Prostephanus truncatus and its new distribution areas in Africa, much work remains to be done. The workshop recommends further research concerning ecosystems analysis with particular emphasis on:
- Taxonomy and host ranges of the pest / natural enemies
- Geographical and ecological boundaries
- Socio-economic impact assessment
- Population dynamics and life cycle studies of P. truncatus, its competitors and its antagonists
- Host plant-pest interactions in field and stores
- Farming and storage practices including use of insecticides
- Further development of pheromone trapping techniques
- Rearing and release technologies for promising natural enemies
The workshop also recommends training at various levels in:
- insect identification of storage pests and natural enemies
- rearing and release methods
- monitoring and survey techniques
- crop loss and impact assessment in close association with the aforementioned research.
4. Subject: Donor awareness.
Despite the research, control and containment already undertaken, the LGB remains a serious threat to food security in Africa and is still extending it's distribution range. Every effort must be made to develop an integrated approach to reduce losses to acceptable levels.
Many countries do not have the infrastructure, research capabilities or adequate funds to effectively deal with the problems caused by LGB. Therefore the donor community and international organisations are urged to provide support for the implementation of the above mentioned recommendations.