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Heavy metals in fungicides are impacting insecticide efficacy

A University of Wisconsin researcher says there is a correlation between fungicides and the ability for potato beetles to develop insecticide resistance.  Professor and Extension Entomologist Russell Groves tells Brownfield insects are exposed to a myriad of different inputs in the field, and he’s not sure what other insects might be developing insecticide resistance. Groves says, “The extent to which that it happens across other insects is really unknown right now. Just in our investigations, I can tell you that we do see this obvious effect in terms of decreasing the susceptibility to insecticides after exposures to some of these fungicides.”

Groves says they noticed the pattern of resistance when looking at different geographical areas. “We saw this very east-to-west difference in the relative susceptibility, and one of the most obvious differences was the amount of fungicides applied in the east versus the west, so it led us in that direction to look for that.”

Groves says the fungicides containing copper, manganese, magnesium, and zinc decreased the efficacy of insecticides.  He says insects might be excreting the insecticide before it can affect them, or there might be microbial breakdowns of the insecticide within the insect.  Groves says it’s possible the metals from fungicides might be changing the microbial composition inside insects, as metals and bacteria generally don’t go well together.

Groves spoke to Brownfield at the recent Wisconsin Potato and Vegetable Growers Association conference.