Molasses grass (Melinis minutiflora), a non-host plant to stemborers, is reported to produce volatiles that attract stemborer parasitoids [1]. The foraging behavior of the stemborer pupal parasitoid (Dentichasmias busseolae) was investigated in a maize monocrop and in an intercrop of maize and molasses grass. These studies were conducted to determine whether the presence of the non-host plant would interfere with the location of infested host plants by the wasp.

Individual female parasitoids were given the opportunity to sample the two crop arrangements under semi-field conditions. Two classes of behavioral elements - the behavior and position of the parasitoid - were continuously recorded using The Observer 3.0 software. The following wasp behaviors were observed and recorded, along with whether they occurred on the test plants or elsewhere: fly, walk, stand, groom, antennate, window-bite and enter hole.

Analyses were performed to test for differences in foraging behavior between the monocrop and the intercrop. In both cropping systems, infested plants were visited more often and for longer periods. There was no significant difference between the total time spent on uninfested plants and non-host plants. While on infested plants, wasps spent most time engaged in activities related to host location.

These investigations show that the presence of the non-host plant did not significantly interfere with the ability of D. busseolae to locate herbivore-infested plants in an intercrop, even though it took slightly longer for wasps to find the infested plant in the intercrop than in the monocrop. Hence, at least over short distances, the parasitoid seems able to distinguish the odours of its host plant.

References

1. Khan, Z.R.; Ampong-Nyarko, K.; Chiliswa, P.; Hassanali, A.; Kimani, S.; Lwande, W.; Overholt, W.A.; Pickett, J.A.; Smart, L.E.; Wadhams L.J.; Woodcock, C. (1997). Intercropping increases parasitism. Nature, 388, 631-632.

Paper presented at Measuring Behavior 2002 , 4^th International Conference on Methods and Techniques in Behavioral Research, 27-30 August 2002, Amsterdam, The Netherlands

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