Rationale: Experiment evidence for efficacy of Metarhizium against Desert Locust and confirmation of efficacy against grasshoppers and other locusts.
2.A: Develop experimental formats for Desert Locust trials
2.A.1 Hopper band movements
The daily migration of at least 15 hopper-bands in Mauritania were observed by watchman using GPS. Sizes of the bands varied between 10,000 and 6 Mil. individuals. The distances covered daily depended on various biotic and abiotic factors such as type and density of vegetation, moulting events, predator attacks, temperature, wind speed and direction. In the observation areas south east of Nouakchott with dunes and a vegetation coverage of 40+ 10%, bands migrated 1.3 + 0.2 km per day. During moulting the distances were less than 200 - 300 m. The daily direct lines between morning and evening resting places varied between 300 and 1500m, indicating that the bands did not move in a straight line. In nearly 50% of the observations, they moved in circles of followed zigzag courses. These changes of direction were caused either by predator attacks or moulting events (which involves searching for favourable moulting bushes. (Wilps and Achmedou, IN PREP)
2.A.2: Food competition between SGR and livestock
In the areas described, nearly 100 plant species were recorded (annual and perennial), and the food preferences of SGR determined (Culmsee and Wilps, IN PREP). Nearly 1/3 are preferred by both SGR and livestock, 1/3 only by SGR and 1/3 only by livestock. This implies a lack of severe competition; particularly between locusts and camels, and it is likely that treatments of pastures in order to secure food resources for livestock is probably not economically worthwhile. Methods used in the study include observations of food intake by bands, feeding behaviour of hoppers in plastic fenced areas with various plant societies, questioning of live stock breeders. (Wilps, Culmsee and Achmedou, IN PREP.)
2.A.3: Estimation of hopper band sizes
Methodology developed by Langewald et al has been published (Langewald et al, 1997).
However, the method is quite time-consuming and involves computer processing of scanned photographs. Various methods of estimating numbers of individuals in hopper-bands were further tested in Mauritania, including counting of hopper numbers in defined rectangles during migration, collection at resting places, evaluation of slides, collecting and counting motionless hoppers in early morning. In 50 - 70% of the cases, correct data could be obtained, but in any case, each method is very time consuming. During normal control measurements, in times of outbreaks or plagues only rough estimations can be done (Wilps and Achmedou, IN PREP).
2.A.4 Influence of predators
During the observations mentioned above, 5 hopper-bands with up to 40,000 individuals were lost entirely due to predator activities. Most impressive was the loss of 2 bands with 300,00 and 400,000 individuals respectively by colonies of breeding golden sparrows. Other important predatory birds are Cursoris cursor, Passer simplex sahara, two lark species and two Shrike species. Other predators have been: predatory arthropods and lizards. Artificially reared hopper-bands containing up to 20,000 individual and released as 3rd instars were consumed in 3 to 4 days. Combined with further field observations it can be stated that bands of the first instar level containing 200,000 individual or less will, due to predator activities, never undergo adult moult. (Wilps, Achmedou and Culmsee, IN PREP).
2.B: Field experiments to confirm efficacy of Metarhizium
2.B.1 Mauritania; Secondary pickup
Laboratory and semi-field trials measuring secondary pickup (uptake from contaminated vegetation) resulted in laboratory mortality of 40%, even up to 4 days after application. Longer duration trials failed for technical reasons and will be repeated this year. Semi-field trials in plastic fenced areas pointed in the same direction, but couldn't be evaluated properly due to the attacks of predatory wasps, which entered the open-top cages and removed the hoppers (Wilps and Kane, IN PREP).
Laboratory experiments also examined the pick-up of Metarhizium spores during copulation (Kane and Wilps, IN PREP).
2.B.2 Sudan
Trials in Sudan were conducted in January 1998 in collaboration with ICIPE, testing pheromones plus Metarhizium. Results were promising; the pheromone causes the treated band to move more slowly and reduces aggregation. Both of these behavioural effects increase predation. Technical issues concerning the pheromone remain to be resolved (toxicity testing and economic evaluation). A full report is expected.
2.B.3 Maine Soroa, Niger
In 1997, unreplicated 800 ha plots were treated by air with Metarhizium or Fenitrothion (Figure 5). 1998 trials focussed on an ecotoxicological comparison with Fipronil, and new and widely used acridicide, currently being aggressively promoted by Rhone-Poulenc. Data were also collected on yield loss, but low grasshopper attack will probably mean that differences will not be significant.
2.B.4 Mali – Dose rate
Trials were conducted on varying spore dose rates in Mali in 1998 (Douro-Kpindou et al., (9)). There was no significant difference between the effect of 100g/l and 50g/l doses. 20g/l was less effective.
2C: Training national counterparts
The LUBILOSA team based at DFPV/AGRHYMET maintains an important biocontrol component within the DFPV training programme.
Mr. Kone of the Mauritania DPV came to Cotonou for bench training in April/May 1998.
The principal training activities are the collaborative trials described under Output 5.