| Scope and method of study. Three different studies were performed to determine the greenbug host plant resistance influence on the third trophic level, composed by greenbug predators and parasitoids. In the first study, the olfactory reaction of female adult parasitoids (Lysiphlebus testaceipes) was checked with odors originated from resistant and susceptible sorghum plants and greenbugs. In the second study, the development of immature stages, mummy and adult sizes, and fecundity of the parasitoids were studied, during five generations, on greenbugs reared on resistant and susceptible sorghum and barley plants. In the third study, the preimaginal development and initial adult weight of the predator Hippodamia convergens were studied during four generations, feeding on greenbugs reared on resistant and susceptible sorghum and barley plants.;Findings and conclusions. In the olfaction study, the results suggest that adult female parasitoids do not react to plant odors alone. The odor of greenbugs plus plants is necessary to trigger the host searching behavior. In the second study, fecundity, efficiency in parasitization, and adult emergence were greatly reduced by the influence of resistant barley. Reduced body size and increased development time was the effect of both barley and sorghum resistance. In the study with predators, a significant decrease in the initial adult weight was observed along the generations on barley. The total developmental time was longer on barley than on sorghum. No strong effect was observed from the resistant plants. |
