Dimethoate, fenvalerate and their mixture affects Hylyphantes graminicola (Araneae: Linyphiidae) adults and their unexposed offspring

Abstract

1 Mixtures of organophosphorus and pyrethroid insecticides are widely used to combat resistance in agricultural pests, although few studies have been conducted on the effects of pesticide mixtures on beneficial nontarget organisms. 2 In the present study, we exposed adult females (F 0 ) of Hylyphantes graminicola (Araneae: Linyphiidae) to fenvalerate, dimethoate and their commercially available 1 : 1 mixture (by mass). We investigated the acute toxicity of these pesticides to the exposed adults, as well as sublethal effects on reproduction and acetylcholinesterase and carboxylesterase activity. We also studied the effects of parental exposure on the size, development and enzyme activity of unexposed offspring. 3 All three formulations were acutely toxic to H. graminicola, with synergism between dimethoate and fenvalerate leading to greater toxicity in the 1 : 1 mixture than for the two insecticides alone. The sublethal effects of direct pesticide exposure were a reduction in acetylcholinesterase and carboxylesterase activity and a reduction in the number of egg sacs produced by exposed spiders relative to the control spiders. The unexposed offspring of the fenvalerate and mixture exposed spiders were smaller and took longer to mature than the control spiders. Offspring of all exposed spiders also had significantly reduced carboxylesterase activity relative to control spiders. 4 We concluded that the effects of parental exposure on the offspring were likely to increase their susceptibility to future pesticide exposures, and reduce the capacity of this spider to serve as a pest control agent.

Imidacloprid Affects Pardosa Pseudoannulata Adults and Their Unexposed Offspring

“…Our results showed that a low dose of imidacloprid might cause an increase of CarE activity and lead to an increase in the prey-capture ability of P. pseudoannulata. AChE is a target enzyme of organophosphate and carbamate insecticides (Peng et al 2010). Here, we found that P. pseudoannulata had lower AChE activity when treated with imidacloprid, and these results were negatively related to their higher susceptibility to the insecticides that were tested.…”

“…In this experiment, the spiders surviving after 5 days immersed in imidacloprid were used to make the preparations for assaying the activity of enzymes. CarE activity was measured using the method described by Peng et al (2010). AChE activity was measured essentially according to the method of Ellman et al (1961), and MFO activity was measured according to Chang and Hodgson (1975).…”

“…In spiders, the observed effects of pesticides also involve changes at the cellular level, including the inhibition of carboxylesterase (CarE) and acetylcholinesterase (AChE) (Babczynska et al 2006;Peng et al 2010). The activities of CarE, AChE and MFO are widely used as biomarkers of pesticide exposure in a range of biota (Hyne and Maher 2003;Peng et al 2010).…”

“…The activities of CarE, AChE and MFO are widely used as biomarkers of pesticide exposure in a range of biota (Hyne and Maher 2003;Peng et al 2010).…”

Appraisal of the Impact of Three Insecticides on the Principal Rice Pests and Their Predators in China

“…In order to reduce the effects of pesticides on non-target insects, rice pest control methods need to be improved. Application of insecticide mixtures is an effective strategy to manage several insects simultaneously and possibly to reduce total insecticide use (Han et al 1993;Corbel et al 2004;Peng et al 2010). Such mixtures have been widely used to manage pests in agriculture.…”