The toxicity of some benzimidazole fungicides to the pea aphid, Acyrthosiphon pisum

Abstract

S U M M A R YField bean plants were treated with benomyl in a glasshouse and nymphs of Acyrthosiphon pisum were then caged on the second pinnate leaf. Soil drenches of 75 pg benomyl/ml or above increased mortality of the aphid. The concentration of methyl benzimidazole-2-yl carbamate (MBC = carbendazim) in leaf sap, determined by a Penicillium expansum bioassay, was proportional to the concentration of benomyl applied as a soil drench or foliar spray, but lower in sprayed plants than drenched plants. The compound persisted at high concentrations in the second leaf for 4 wk but was present in low amounts in young leaves. Nymphs were also fed through membranes on artificial diets incorporating benzimidazole compounds. In this artificial system a commercial formulation of carbendazim (Bavistin) increased aphid mortality whereas the formulation medium was inactive. Thiabendazole (as the commercial formulation Tecto 60), 2-aminobenzimidazole and benzimidazole were also inactive. It is suggested that the carbamate moiety of carbendazim causes the aphicidal activity of the compound.

Fungicides have transgenerational effects on Rhopalosiphum padi but not their endosymbionts

“…Despite none of the fungicides trialed here significantly affecting Buchnera or Rickettsiella within R. padi , there remains a range of fungicides and other chemicals with known antibacterial properties that are yet to be tested on aphid endosymbionts. Some studies have shown other fungicides ( e.g ., azole fungicides) to impact aphid fitness, 46,47,91 but whether these fitness effects are mediated by endosymbionts is yet to be explored. Previous studies have demonstrated other pesticide treatments disrupt the relationship between pest insects and their endosymbionts 42,51,92 .…”

“…An increasing number of fungicides are known to have sublethal impacts on arthropods (and other animals) due to fungicides impacting their bacterial microbiome. [42][43][44][45] Some fungicides have sublethal effects on aphids, [46][47][48] although the involvement of endosymbionts in mediating these sublethal impacts remains unclear since fungicides can also possess insecticidal qualities that directly harm aphids.…”