Lethal and Sublethal Effects of Two Commercial Insecticides on Egg Parasitoids (Hymenoptera: Scelionidae) of Green Stink Bugs (Hem: Pentatomidae)

Abstract

Pistacia vera L. is one of the most important horticultural crops in Iran. The stink bugs Acrosternum arabicum and Brachynema germari are two of the key pests that cause significant direct and indirect damage on Pistacia vera. Egg parasitoids have been considered as potential biological control agents of pistachio green stink bugs. Among them, Trissolcus semistriatus and Psix saccharicola are the most abundant and efficient parasitoid for A. arabicum in pistachio orchards. In this study, we assessed lethal and sublethal effects of two commonly used insecticide products (fenitrothion and a binary mixture of lambda-cyhalothrin + thiamethoxam) on these two parasitoid wasps under laboratory conditions. The median lethal concentration (LC50) values for fenitrothion and thiamethoxam + lambda-cyhalothrin in P. saccharicola and T. semistriatus were estimated as 1.03, 0.48 and 0.87, 0.98 mg a.i./liter, respectively. In terms of sublethal effects, insecticide treatments altered the type of functional response from type III to type II in T. semistriatus. However, P. saccharicola exhibited a type II functional to density of A. arabicum for all treatments, although attack rates were lower for insecticide-exposed wasps while handling times increased. Our results show that sublethal effects of insecticides further reduce the efficacy of biological control agents. Effective integrated pest management programs should avoid antagonistic interactions between chemical and biological control methods. The results of this study provide useful information to develop comprehensive integrated pest management programs for stink bugs in pistachio orchards.

Biological Control May Fail on Pests Applied with High Doses of Insecticides: Effects of Sub-Lethal Concentrations of a Pyrethroid on the Host-Searching Behavior of the Aphid Parasitoid Aphidius colemani (Hymenoptera, Braconidae) on Aphid Pests

“…However, contrary to our results, some studies reported that pyrethroids disrupt locomotor function and parasitoids' physical perception [20,71,72]. For instance, pyrethroids insecticides at sub-lethal doses could disturb some behavior parameters, decreasing the attack rates of Trissolcus semistriatus (Hymenoptera, Platygastridae) [73], the walking speed in Trissolcus basalis (Hymenoptera, Platygastridae) [20], and the oviposition behavior of A. ervi parasitizing M. persicae on oilseed rape [52]. An explanation of our results could be that parasitoid wasp rearing began from the mummies of M. persicae collected on peach orchards.…”

Sublethal effects of bifenazate on biological traits and enzymatic properties in the Panonychus citri (Acari: Tetranychidae)

“…Our toxicity assay results showed that bifenazate is a potential insecticide for effective control of P. citri ; However, insecticide has not only acute toxicity, but also the sublethal effects 38 . In the current study, the fecundity of P. citri was decreased in the LC 10 or LC 30 treated groups, and the same response was observed in pests treated with other insecticides 39 .…”

Functional response of an egg parasitoid,Trichogramma chilonisIshii to sublethal imidacloprid exposure

“…brassicae were fed to eggs of Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) treated with Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) 78 and eggs of Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae) treated with LC 30 of diazinon 76 . Apart from Trichogramma , a shift in the functional response was also observed for other parasitoids and predators under the exposure of different concentrations of different insecticides 82–84 . The difference in the type and parameters of functional response is due to various factors, namely exposure to pesticides, bio‐agents under study, multigenerational and transgenerational effects, differences in the host species, and laboratory conditions 46,63,84 …”

“…76 Apart from Trichogramma, a shift in the functional response was also observed for other parasitoids and predators under the exposure of different concentrations of different insecticides. [82][83][84] The difference in the type and parameters of functional response is due to various factors, namely exposure to pesticides, bio-agents under study, multigenerational and transgenerational effects, differences in the host species, and laboratory conditions. 46,63,84 Despite a change in the type of functional response upon exposure to different concentrations of insecticide, it resulted in increasing (except for the LC 50 ) the asymptote of the functional response curve as compared to the control.…”