Sublethal Effects of Some Insecticides on Functional Response of Habrobracon hebetor (Hymneoptera: Braconidae) When Reared on Two Lepidopteran Hosts

Abstract

The effects of four commonly used pesticides, diazinon (EC 60%), phosalone (EC 35%), fipronil (Granular formulation 0.2%), and pyriproxifen (EC 10%), on functional response of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) were investigated using two lepidopteran hosts, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and Heliothis viriplaca (Hufnagel) (Lepidoptera: Noctuidae). Laboratory bioassays determined diazinon and fipronil as highly toxic insecticides for all developmental stages of the parasitoid, while the acute toxicity of phosalone and pyriproxyfen was moderate to very low depending on the life-stage studied. Larval, pupal, and adult stages of the parasitoid were exposed to sublethal concentrations (LC30) of insecticides, and the newly mated females were used to study functional response of the parasitoid to different host densities. With a single exception, a type II functional response was found for control and all insecticide treatments on all life stages and both host species. All insecticides tended to decrease the asymptote of the functional response curve and the maximum parasitism rate, probably by negatively affecting the searching efficiency (a') of the parasitoid. These results indicate that the control efficiency of parasitoids may be negatively affected by sublethal doses of pesticides, even though the type of functional response remains unchanged. As a potential solution, appropriate timing of pesticide application is required to avoid the antagonistic interactions with natural enemies under integrated management programs.

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

“…The attributes of the success of a biological control agent not only depend on its ability to manage pests but also on its compatibility with other pest management methods, especially chemical management. 63 The importance of bio-control agents in IPM has resulted in the development of various methods for estimating the effects of insecticides on the bio-control agents. The degradation of insecticides due to rainfall, high temperature, sunlight, etc., alters the target concentrations of the insecticides, thereby resulting in lethal as well as sublethal concentrations.…”

“…Parasitoids with higher searching efficiency and lower handling time are considered to be better bio-agents. 63,81 The coefficient of attack rate is positively correlated with searching efficiency and negatively with the handling time of a bio-control agent, thereby resulting in searching efficiency and handling time being maximum and minimum, respectively. 23 This further resulted in increasing the asymptote of the curve, thereby indicating a higher attack rate by a bio-agent on the targeted host/prey.…”

“…[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. These results were in line with the research carried out on other parasitoids.…”

Laboratory assays on the effects of a novel acaricide, SYP-9625 on Tetranychus cinnabarinus (Boisduval) and its natural enemy, Neoseiulus californicus (McGregor)

“…This result differed from other studies such as Rashidi et al which found that sublethal doses of four pesticides negatively affected the control efficiency of Habrobracon . Hebetor [ 47 ]. It might due to the weak toxicity of SYP-9625 against N .…”

Sublethal effects of some insecticides on the functional response of Aenasius bambawalei Hayat, 2009 (Hymenoptera: Encyrtidae)

“…: Braconidae) (Rezaei et al, 2014), Habrobraon hebetor Say, 1836 (Hym. : Braconidae) (Abedi et al, 2012, Mahdavi et al, 2013, Rashidi et al, 2018, Dolichogenidea tasmanica (Cameron, 1912) (Hym. : Braconidae) (Paull et al, 2014), and Eretmocerus mundus Mercet, 1931 (Sohrabi et al, 2014) have been reported in previous studies.…”