Pesticide side-effects on predatory mites: the role of trophic interactions

Abstract

465The control of spider mites in protected crops is often critical due to the development of mite resistance to acaricides. Studies of the side-effects of pesticides on beneficial mites are required in order to improve integrated spider mite management. Pesticide side-effects on predatory mites of the family Phytoseiidae can be studied at the field or laboratory level. In the field, phytoseiid abundance can be related to the presence of prey and/or alternative foods, which can affect the response of predatory mites to pesticides. We investigated whether pesticide side-effects on phytoseiids may be mediated by trophic interactions. In the laboratory we evaluated the effects of two insecticides (derived from pyrethrins and Beauveria bassiana) on the predatory mite Phytoseiulus persimilis by testing the same under various exposure conditions (leaf residues, treated prey, topical application). The effects of these insecticides on P. persimilis were higher when the predators were fed with treated prey. Furthermore, we investigated the effects of pyrethrins on the predatory mite Amblyseius andersoni on vines with low or high incidence of the plant pathogenic fungus Plasmopara viticola (grape downy mildew, GDM). GDM mediated interactions between pyrethrins and A. andersoni since it is alternative food for this predatory mite. The implications of these studies for the development of toxicological methods and integrated pest management are discussed.

Side Effects of Insecticides on Natural Enemies and Possibility of Their Integration in Plant Protection Strategies

“…In contrast, the total effect of all concentrations of fenpyroximate, and field, as well as, one half the field concentration of abamectin were found toxic to predatory mite and above upper threshold. The overall results confirmed that P. persimilis is promise and crucial to develop IPM programs in agricultural crops; similar results were obtained by (Cloyd et al 2006, Pozzebon & Duso 2010.…”

Compatibility of Amblyseius swirskii with Beauveria bassiana: two potentially complimentary biocontrol agents

“…The studies reported susceptibility with slight to moderate virulence to P. persimilis after observation periods of three days (Duso et al 2008), six days (Pozzebon and Duso 2010) and 12 days (Numa Vergel et al 2011). Only Ludwig and Oetting (2001) reported high virulence to P. persimilis exposed to topical treatment of B. bassiana with 100 % mortality, although time of death and sporulation was not mentioned.…”

“…Offspring of arthropods infected with B. bassiana may exhibit reduced survival and fecundity, moulting problems and malformations (Torrado-Leon et al 2006). Egg hatching success can be significantly reduced for gravid B. bassiana-treated N. californicus (Castagnoli et al 2005) and P. persimilis (Pozzebon and Duso 2010), but, contrary to these findings, treatment of P. persimilis with B. bassiana has also been reported to have no effect on egg hatching success (Duso et al 2008;Seiedy et al 2012). The results of the current study are consistent with the latter: no significant effect was observed on egg viability, juvenile survival or the sex ratio of offspring from B. bassiana-treated A. swirskii.…”

“…Female adults of A. swirskii, age 2-4 days, were exposed to B. bassiana by topical application, dry residue on P. vulgaris leaf discs or a combined exposure with topical application followed by dry residue exposure, inspired by the methods of Dennehy et al (1993) and Pozzebon and Duso (2010) as described below. The trial arenas (leaf discs in 50 mm Petri dishes) were incubated at 25°C, 90 % RH and 16:8 L:D to maximise the likelihood of fungal infection.…”

“…Interactions between arthropods and entomopathogens are however complex (Agboton et al 2013;Aqueel and Leather 2013) and the impact of sublethal effects is poorly understood (Pozzebon and Duso 2010;Seiedy et al 2012;Shipp et al 2012). The aim of this study was to establish the potential of the commercially available B. bassiana strain GHA to infect and kill A. swirskii under optimal conditions for the pathogen and to investigate the effects on specific population parameters when subjected to topical application of B. bassiana conidial suspensions and/ or dry residues on leaf discs.…”