A review of pesticide effects upon immature aphid parasitoids within mummified hosts

Pyrethroid Insecticides: Use, Environmental Fate, and Ecotoxicology

“…Authors noted that in this hymenopteran species, females are produced by fertilized eggs, while unfertilized eggs produce males, and that the behaviors associated with egg fertilization may have been impacted by the insecticide exposure (Desneux et al, 2007). However, data from field studies indicate that sublethal effects of pyrethroid exposure may not have large-scale impacts on overall parasitoid population viability (Li et al, 1992, Longley, 1999.…”

Sublethal Effects of Pyrethroids on Insect Parasitoids: What We Need to Further Know

“…Reductions in longevity have been generally observed in parasitoids that had been exposed to insecticides when developing inside of hosts (Longley, 1999;Desneux et al, 2006ab;Ergin et al 2007). The consequences of reduced longevity on population dynamics were recently emphasized by studies assessing pesticide impacts on arthropods using life table analysis, given that a decrease in survival may result in a strong reduction on the natural enemy's intrinsic rate of increase (Stark et al, 2007b).…”

“…The female parasitoid oviposits into the host but the aphid is only killed prior to parasitoid pupation, being only kept the skin of the host, termed as mummy. The parasitoid then completes the development to adult, which emerges from the host (Longley, 1999). The immature stages (egg, larva and pupa) of both egg and aphid parasitoids can be often protected from insecticide applications since parasitoids are housed within the host egg chorion or host skin during their development, being therefore key stages for IPM programs.…”

“…Pyrethroids are considered harmful (mortality >99%) to insect parasitoids, particularly to adults; nevertheless, when testing the less susceptible life stages of endoparasitoids (e.g., larval or pupal stages), there is reduction in the mortality, lowering the evaluation category to slightly harmful (30-70% of mortality) (Sterk et al, 1999). According to the review made by Longley (1999), organophosphate insecticides prove to be generally more toxic to developing aphid parasitoids within mummified hosts than pyrethroid compounds (pyrethroids were included by the authors in a rank that gives mortalities between 21-30%, while organophosphates ranked for mortalities between 51-60%). However, even if immature stages of insect parasitoids might be less susceptible to pyrethroids, these insecticides most probably have effects on the wasp's longevity, fecundity, developmental rates, sex ratios, mobility, etc., and therefore such traits should also to be considered when assessing the side effects of insecticides on beneficial organisms.…”

“…In general, field studies have shown that natural enemies, particularly adult parasitoids, are highly affected by pyrethroids, even when these insecticides are applied at a low dosage (e.g., Ruano et al, 2010). However, in the case of endoparasitoids, laboratory trials generally have shown that when pyrethroids are applied on parasitized hosts, their impact on the parasitoids is lowered (e.g., Longley, 1999;Sterk et al, 1999). Even so, their impact on sublethal effects on natural enemies, and consequently the success of biological control programs, can be as deleterious as mortality.…”