Abstract
The use of agrochemicals particularly pesticides, can hamper the effectiveness of natural enemies, causing disruption in the ecosystem service of biological control. In the current study, the effects of the insecticides thiacloprid and chlorantraniliprole on the functional response curves were assessed for two mirid predator nymphs, Macrolophus pygmaeus Rambur and Nesidiocoris tenuis Reuter. In the absence of insecticides, both predators exhibited a type II functional response when feeding on eggs of the moth Ephestia kuehniella. N. tenuis seems to be a more efficient predator than M. pygmaeus, as model estimated handling time was significantly lower for the former than for the latter. Residual exposure of M. pygmaeus to sublethal concentrations of either insecticide was associated with a change in the asymptote but not the type of the functional response curve. Thiacloprid seems to be the least compatible with M. pygmaeus, as it led to both a significant reduction of the attack rate and an increase in handling time. In contrast, chlorantraniliprole exposure significantly increased the handling time, but not the attack rate of the predator. Residual exposure of N. tenuis to sublethal concentrations of either insecticide did not have a significant effect on the type nor the parameters of the functional response model. The results show that pesticide residues that do not have lethal effects on beneficial arthropods can reduce prey consumption depending on predator species and on likely risks associated with toxicity.
Highlights
Pesticides are used globally for arthropod pest suppression and play a major role in integrated pest management (IPM) strategies in many cropping systems
The attack rate was similar between the two predators, but model estimated handling time was significantly higher for M. pygmaeus than for N. tenuis (Table 1)
Pesticide exposure did not alter the type of the functional response, it altered the asymptote of the curve, with a tendency towards lower asymptotes in pesticide treatments compared to the control (Fig 1)
Summary
Pesticides are used globally for arthropod pest suppression and play a major role in integrated pest management (IPM) strategies in many cropping systems. Insect predators are intentionally released or naturally occurring in agricultural fields and offer the important ecosystem service of biological control [1]. In crop systems where pesticides are applied, their compatibility with biocontrol agents is a major concern for IPM practitioners as it is essential for the overall agro-ecosystem resilience to be maintained. Pesticides can cause mortality to many biocontrol agents and the assessment of acute toxicity has long been used in the evaluation of pesticide safety to natural enemies [2]. PLOS ONE | DOI:10.1371/journal.pone.0144413 December 7, 2015
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