Susceptibility of cocooned pupae and adults of the parasitoid Microplitis mediator to selected insecticides

Abstract

The braconid parasitoid Microplitis mediator (Haliday) is a key natural enemy of the cabbage moth, Mamestra brassicae (L.), in Europe. In the context of an Integrated Pest Management approach, the use of selective insecticides is essential for the conservation of naturally occurring beneficial arthropods. The present laboratory study investigated the side effects of six insecticides applied at recommended field rates on adults and cocooned pupae of M. mediator. Male and female parasitoids were paired in drum cells contaminated with dry residues of insecticides. Besides lethal effects after 24 h, parasitization capacity and longevity of the surviving parasitoids was evaluated. Lethal effects on cocooned pupae were also investigated by assessing adult emergence from treated cocoons. Pirimicarb caused 100% adult mortality after 24 h, whereas the other tested insecticides caused no direct toxic effects. However, sub-lethal effects in terms of reduced parasitization activity, percentage of parasitism or female longevity were found for flonicamid, pymetrozine, spinosad and thiacloprid. Spirotetramat shortened only male longevity. Adult emergence from treated cocoons was reduced only by flonicamid and pymetrozine. Keywords Flonicamid . Pirimicarb . Pymetrozine . Spinosad . Spirotetramat . Thiacloprid The cabbage moth, Mamestra brassicae (L.), is a key pest of Brassica crops and frequently causes serious economic damage (Pfiffner et al. 2009). Several parasitoids have been reported to attack M. brassicae in European cabbage crops. The braconid Microplitis mediator (Haliday) is an endoparasitoid of M. brassicae larvae (Lauro et al. 2005) and reportedly the species with the highest constancy and abundance in central Europe (Turnock and Carl 1995). Although natural control exerted by M. mediator may be substantial, additional insecticide treatments remain necessary to control M. brassicae and other key pests in Brassica crops. Knowledge of the side effects of chemical pesticides on beneficial arthropods is therefore crucial. Assessment of a compound's non-target effects should include both direct toxicity and sublethal effects (Desneux et al. 2007). Little is known about the toxicity of spinosad and several novel aphicides registered for use in Brassica crops to M. mediator. The present study examined the lethal and sub-lethal effects of four biorational (flonicamid, pymetrozine, spinosad, spirotetramat) and two conventional (thiacloprid and pirimicarb) insecticides on this parasitoid. Effects of these pesticides were tested both on adult parasitoids and cocooned pupae.Microplitis mediator was collected in Brassica fields in Belgium and cultured using M. brassicae Phytoparasitica (2012) 40:5-9

Lethal and sublethal effects of spirotetramat on the mealybug destroyer, Cryptolaemus montrouzieri

“…Although there is little information about the side effects of spirotetramat on other natural enemies, the available studies have similarly categorized this lipid biosynthesis inhibitor as harmless to other natural enemies, such as the predators Episyrphus balteatus (Degeer) (Diptera: Syrphidae) and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) (Schnorbach et al 2008;Moens et al 2011) and the parasitoids Microplitis mediator (Haliday) (Hymenoptera: Braconidae), Coccidoxenoides perminutus Girault (Hymenoptera: Encyrtidae) and Anagyrus sp. near pseudococci (Hymenoptera: Encyrtidae) (Mansour et al 2011;Moens et al 2012). Therefore, based on these results, and on the side effects observed in our study, spirotetramat could be included in IPM programs where C. montrouzieri is a key natural enemy.…”

Lethal and Sublethal Effects of Various Pesticides on Trichogramma achaeae (Hymenoptera: Trichogrammatidae)

“…Merthiocarb and methomyl also increased female infertility rate. Different studies have reported that pirimicarb did not affect the biological parameters of T. pretiosum (Carvalho et al 2001), however, other authors found that this product caused high mortality when adults of other parasitoids were exposed to dry residues or the direct spray method (Desneux et al 2004, Moens et al 2012. Bueno et al (2008) demonstrated that methomyl significantly reduced parasitism viability when applied in the T. pretiosum immature stages.…”

Activity of flonicamid on the sweet potato whitely Bemisia tabaci (Homoptera: Aleyrodidae) and its natural enemies

“…For example, no or negligible reduction in survival was observed in the ground beetle Bembidion lampros, 12 the coleopteran predator Cryptolaemus montrouzieri, 13 the rove beetle Atheta coriaria 14 or the parasitoid Microplitis mediator. 15 Also, the parasitoid Leptomastix dactylopii 13 and the hoverfly Episyrphus balteatus 12,16 suffered neither mortality nor sublethal effects due to flonicamid. However, several authors have reported lethal and sublethal effects on non-target organisms from a range of taxa.…”