Fungicides usually are not a cause of concern for honey bee poisoning. At labeled field application rates, captan sometimes is associated with larval and pupal mortality. Honey bee broods are lost at a time when the colony population should be expanding. Studies by staff at the USDA Bee Lab in Weslaco, TX, show that honey bee impacts due to captan are related to formulation. These results suggest that it is not the captan itself, but other ingredients in some formulations, that cause developmental problems. These findings are under review for publication.
Iprodione (Rovral) is another fungicide of concern. During studies at University of California–Davis, some honey bee larvae died when exposed to iprodione. Others develop into large, robust pupae that do not develop into adult forms. Other dicarboximide fungicides might affect bees similarly, but such effects have not been determined experimentally.
Fungicides containing captan or iprodione should not be applied to blooming crops during the pollination period.
Certain combinations of demethylation-inhibiting (DMI) fungicides, such as propiconazole (Alamo, Propimax, Quilt), with synthetic pyrethroids, such as lambda-cyhalothrin (Taiga Z, Warrior) have been shown in the laboratory to be more toxic to bees than the insecticide alone (Pilling and Jepson, 1993) because these fungicides reduce the ability of the bee to detoxify the insecticide (Pilling et al., 1995). It is essential that growers read the pesticide label to determine whether specific tank mixes might prove toxic to bees. These problems might also arise if neighboring crops have been treated separately with two materials that can prove hazardous when they are combined.
2010 Pest Management Guide FOR TREE FRUITS IN THE MID-COLUMBIA AREA
Hood River • The Dalles • White Salmon EM 8203-E • Revised January 2010