Maruca

Abstract: The legume pod borer, Maruca(testulalis) vitrata (Geyer) is one of the major limitations to increasing the production and productivity of grain legumes in the tropics. Bionomics, host-plant resistance, natural enemies, cultural practices, and chemical control of the legume pod borer have been discussed in this bulletin to identify gaps in present knowledge and to help plan future strategies for research on this pest on pigeonpea. While information is available on bionomics and host-plant resistance in cow pea, such information on pigeonpea and other legumes is limited. Several natural enemies have been recorded on M.vitrata,and pathogens such as Bacillus thuringiensis, Nosema, and Aspergillus play an important role in regulating its populations under field conditions. Cultural practices such as inter-cropping, time of sowing, density of sowing, and weeding reduce the pod borer damage. Several insecticides have been found to be effective for controlling this insect. There is a need to focus future research on standardizing the resistance screening techniques, identification and utilization of resistance, and integrated pest management strategies for sustainable agricultural production.

Abstract: The onset and fluctuation of Maruca infestation on cowpea terminal shoots, flower buds, flowers, and pods was studied under field conditions. Four cowpea cultivars—IFE BROWN, VITA-5, VITA-3, and TVu 946—were used in the study. Infestation started in the terminal shoots around 21 days after planting but later spread to the reproductive parts as these were produced by the plant. The highest infestation was found in flowers > flower buds > terminal shoots > pods. TVu 946 consistently had the lowest number of larvae, and VITA-3 had the highest. It is suggested that TVu 946 may possess a low level of resistance that could be utilized in plant breeding programs.

Abstract: The parasitoid wasp Apanteles taragamae is a promising candidate for the biological control of the legume pod borer Maruca vitrata, which recently has been introduced into Benin. The effects of volatiles from cowpea and peabush flowers and Maruca vitrata larvae on host selection behavior of the parasitoid Apanteles taragamae were investigated under laboratory conditions by using a Y-tube olfactometer. Naive and oviposition-experienced female wasps were given a choice between several odor sources that included (1) uninfested, (2) Maruca vitrata-infested, and (3) mechanically damaged cowpea flowers, as well as (4) stem portions of peabush plants carrying leaves and flowers, (5) healthy M. vitrata larvae, and moribund (6), and live (7) virus-infected M. vitrata larvae. Responses of naive and oviposition-experienced female wasps did not differ for any of the odor source combinations. Wasps were significantly attracted to floral volatiles produced by cowpea flowers that had been infested with M. vitrata larvae and from which the larvae had been removed. Apanteles taragamae females also were attracted to Maruca vitrata-infested flowers after removal of both the larvae and their feces. Female wasps discriminated between volatiles from previously infested flowers and mechanically damaged flowers. Uninfested cowpea flowers attracted only oviposition-experienced wasps that had received a rewarding experience (i.e. the parasitization of two M. vitrata larvae feeding on cowpea flowers) before the olfactometer test. Wasps also were attracted to uninfested leaves and flowers of peabush. Moreover, they were also attracted to healthy and live virus-infected M. vitrata larvae, but not when the latter were moribund. Our data show that, similarly to what has been extensively been reported for foliar volatiles, flowers of plants also emit parasitoid-attracting volatiles in response to being infested with an herbivore.