Effects of vegetational diversity on a native, generalist insect herbivore, Lygus hesperus (Hemiptera: Miridae), in an agricultural system and applications to cultural and biological control

Diversity in the agricultural landscape has the potential to depress insect herbivore populations and reduce crop damage, but realization of this potential depends on the host plant(s) used to increase diversity. This dissertation presents research investigating vegetational diversity in blackeye beans for management of the insect herbivore pest, Lygus hesperus Knight (Hemiptera: Miridae). We tested the efficacy of using a trap crop mixture to attract the herbivore from the blackeye beans and found that the trap crop (a) was not consistently attractive to reduce L. hesperus populations in the beans, and (b) may be more effective if mortality in the trap habitat were higher than in the crop habitat. Consequently, in a second study, we studied differences in both L. hesperus oviposition and parasitism of L. hesperus eggs by the parasitoid, Anaphes iole Girault (Hymenoptera: Mymaridae) among eight different host plants. Oviposition was as high on Amaranthus retroflexus L. (Amaranthaceae) (pigweed) as on blackeye beans and egg parasitism was higher, so we selected this plant species to interplant with blackeye beans in a subsequent study. In this third study, we interplanted blackeye beans and pigweed in two ratios (80:20 and 50:50) and measured L. hesperus abundance, crop damage, and L. hesperus egg parasitism by A. iole. Neither ratio worked to reduce damage to the field crop. Herbivore mortality by parasitoid attack was too low on pigweed to effectively reduce L. hesperus abundance in interplanted plots. Together, these studies suggest that vegetational diversity in blackeye beans has the potential to reduce L. hesperus abundance and bean damage, but determining how this potential may be fulfilled will require further study. Future work with pigweed could focus on the mechanisms underlying natural enemy attack on this host-plant species toward a goal of creating consistency in attack among years. Research could also investigate other host-plant species on which natural enemy attack may be high but vary less between years. Planting time and phenology of the alternative plant species relative to the crop may also be important in influencing herbivore population growth and natural enemy attack and warrants further investigation.