Abstracts (first author)
Can parasitoid recognition of hosts be improved by conditioning to host mate-recognition cues?
Species-specific semiochemicals, such as mate recognition pheromones, are often exploited by predators and parasitoids as cues for recognizing their prey. Generalist predators, unlike their prey, respond to pheromones of many prey species. Therefore, generalist natural enemies used for pest management tend to search for alternative prey. This reduces biocontrol efficiency and harms non-target species. We tested whether generalist parasitoids increase parasitism on a specific host after conditioning to its synthetic sex pheromone. Parasitoids learn to associate host presence with related environmental cues. We hypothesized that the efficiency of host search and parasitism would increase at repeated encounter with the learned pheromone odor. Two-phase laboratory experiments tested whether the generalist egg parasitoid Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae) can be conditioned to the synthetic sex pheromone of its host, Lobesia botrana (Lepidoptera: Tortricidae). In the conditioning phase, parasitoids oviposited in L. botrana eggs in the presence or absence of the host's pheromone. In the test phase, wasps of both treatments encountered additional L. botrana eggs, in the presence or absence of the pheromone. Parasitism rates were compared among treatments. Wasps exposed to the pheromone did not increase parasitism rates, neither in the conditioning nor in the test phase. Possibly, the wasps innately responded to the pheromone, which masked their response to conditioning. To examine this possibility, we tried to condition the wasps to rum extract, a neutral olfactory stimulus, foreign to their natural environment. No conditioning occurred in this experiment either, suggesting poor odor learning in T. cacoeciae. We now ask whether chemicals, associated with hosts or host plants, attract the wasps when no conditioning occurs. Olfactometer bioassays are underway to identify environmental cues that guide T. cacoeciae to its L. botrana hosts.