Efficacy of a cry1Ab Gene for Control of Maruca vitrata (Lepidoptera: Crambidae) in Cowpea (Fabales: Fabaceae).

Cowpea [Vigna unguiculata (L) Walp.] is an important staple legume in the diet of many households in sub-Saharan Africa. Its production, however, is negatively impacted by many insect pests including bean pod borer, Maruca vitrata F., which can cause 20-80% yield loss. Several genetically engineered cowpea events that contain a cry1Ab gene from Bacillus thuringiensis (Bt) for resistance against M. vitrata were evaluated in Nigeria, Burkina Faso, and Ghana (West Africa), where cowpea is commonly grown. As part of the regulatory safety package, these efficacy data were developed and evaluated by in-country scientists. The Bt-cowpea lines were planted in confined field trials under Insect-proof netting and artificially infested with up to 500 M. vitrata larvae per plant during bud formation and flowering periods. Bt-cowpea lines provided nearly complete pod and seed protection and in most cases resulted in significantly increased seed yield over non-Bt control lines. An integrated pest management strategy that includes use of Bt-cowpea augmented with minimal insecticide treatment for protection against other insects is recommended to control pod borer to enhance cowpea production. The insect resistance management plan is based on the high-dose refuge strategy where non-Bt-cowpea and natural refuges are expected to provide M. vitrata susceptible to Cry1Ab protein. In addition, there will be a limited release of this product until a two-toxin cowpea pyramid is released. Other than South African genetically engineered crops, Bt-cowpea is the first genetically engineered food crop developed by the public sector and approved for release in sub-Saharan Africa.

Effects of Volatiles from Clavigralla tomentosicollis Stål. (Hemiptera: Coreidae) Adults on the Host Location Behavior of the Egg Parasitoid Gryon fulviventre (Crawford) (Hymenoptera: Scelionidae).

The egg parasitoid Gryon fulviventre is a potential biological control agent of Clavigralla tomentosicollis, a coreid pod-sucking pest of Vigna unguiculata. The host location behavior of naive parasitoid females was studied using a four-armed olfactometer. Two strains of G. fulviventre parasitoids from Burkina Faso and Benin were exposed to odors provided by healthy and infested pods as well as C. tomentosicollis females and males. The time spent in each odor zone was recorded to determine the preference of parasitoid females. Results show that odors from healthy pods, infested pods, and pest females did not attract the parasitoid. However, a significantly attractive response of both strains of G. fulviventre was recorded in the presence of volatiles from males of C. tomentosicollis. Moreover, experiments testing G. fulviventre females' behavior when simultaneously exposed to volatiles from cowpea pods (healthy and infested) and increasing numbers of C. tomentosicollis males revealed a significantly higher attraction of parasitoid females of both strains by volatiles from ten males of C. tomentosicollis. The results suggest that the males of the insect pest emit a pheromone used as kairomone by parasitoids to locate their host. The conditions determining this attractiveness at field level and its impact on host-searching efficiency are discussed.