RESUMO
In biological control, joint releases of predators and parasitoids are standard. However, intraguild predation (IGP) can occur when a predator attacks a parasitoid, potentially affecting pest control dynamics. In addition to the focal prey (FP), Trialeurodes vaporariorum, the intraguild predator (IG-predator) Geocoris punctipes can consume the parasitoid Eretmocerus eremicus (IG-prey). In this IGP context with multiple prey, an alternative prey (AP), like the aphid Myzus persicae, may influence interactions. Theory predicts that, in simple interactions, a predator's functional response (FR) to the FP changes with the presence of an AP. However, whether this holds in an IGP context is unknown. In this study, we empirically tested that prediction. Our results show that without IGP, G. punctipes exhibits a generalized FR with and without AP. Nevertheless, with IGP, the predator exhibited a Type II FR at low and high AP densities, increasing pressure on the FP and potentially favoring short-term biological control strategies. However, when 25 AP were offered, the predator's response shifted, underscoring the importance of monitoring AP densities to prevent potential disruptions in FP control. In both contexts, the increase in AP produced a handling time increase and a decrease in consumption rate. These results indicate that the theoretical prediction of the effect of AP on the FR is met only under specific conditions, and the complexity of multitrophic interactions must be considered.
RESUMO
BACKGROUND: Parasitoids are natural enemies that can modify their behaviors as they search for hosts based on the characteristics of the sites in which they forage. Theoretical models predict that a parasitoid will stay for longer periods in high-quality sites or patches than in those of low quality. In turn, patch quality may be linked to factors such as the number of hosts and the risk of predation. In the present study, we sought to determine if the factors of the number of hosts, risk of predation, and their interaction influence the foraging behavior of the parasitoid Eretmocerus eremicus (Hymenoptera: Aphelinidae) as theory predicts. To do this, we evaluated different parameters of parasitoid foraging behavior, such as residence time, number of oviposition events, and attacks, in sites of different patch quality. RESULTS: Our results show that when the factors, number of hosts, and, risk of predation, were evaluated separately, E. eremicus resided for longer periods and oviposited more frequently in patches with a high number of hosts and low risk of predation than in other patches. However, when both of these factors were combined, only the number of hosts influenced some aspects of the foraging behavior of this parasitoid, such as the number of oviposition events and attacks. CONCLUSION: For some parasitoids like E. eremicus, theoretical predictions may be fulfilled when patch quality is linked to the number of hosts but will not be fully satisfied when patch quality is related to the risk of predation. Furthermore, at sites with different combinations of host numbers and risk of predation, host number appears to be more critical than predation risk. These results suggest that the performance of the parasitoid E. eremicus to control whiteflies will be mainly mediated by the levels of whitefly infestation and, to a small extent, by the risk of predation to which the parasitoid is subjected. © 2023 Society of Chemical Industry.
