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Toxicity of pesticides on pollinators must be minimized

Toxicity of pesticides on pollinators must be minimized

Photo by Laura Melius



Environmental Protection Agency (EPA) has issued a statement concerning use of pesticides and their unintended negative impacts on pollinator health.

This was triggered by a massive kill of bumblebees following applications of pesticides to linden trees to control aphids in Oregon. While this event has received much publicity, pesticides applied to crops kill scores of bumblebees and other pollinators every summer.

This is an important issue for agriculture because there is a large diversity of pollinating insects that provide an invaluable service to crop production, said Ada Szczepaniec, Assistant Professor and Extension Entomologist.

“These include the obvious pollinators that most people are familiar with such as honeybees and bumblebees, as well as many species of native pollinators that are perhaps a little less known,” she said.

Szczepaniec explained that insecticides are toxic to all of these insects, and said it is crucial to minimize exposure of pollinating insects to insecticides.

“Pollinators are attracted to flowering crops, and many insecticides registered for use in alfalfa and soybeans, for example, have warning statements about applying them when these crops are in bloom,” Szczepaniec said. “If the crop you are about to apply insecticides to is in bloom, it is a good time to consider the impact of these applications to pollinators and do all that is recommended to minimize their exposure to these toxins.”

Applying insecticides only when insect thresholds are reached, reading labels carefully, adhering to recommended doses and choosing the least toxic insecticides are steps Szczepaniec said landowners should take to minimize harmful effects of insecticides on pollinators.

Read the label

Pesticide labels typically contain environmental as well as personal hazard information. Buyung Hadi, Pesticide Educator and Urban Entomology Coordinatorpoints to one such environmental hazard label from a pesticide product commonly used on soybeans.

“The emphatic language in the label ‘do not apply to blooming crops or weeds if bees are visiting,’ signifies enforceable restriction. Usage of the product neglecting this restriction is deemed illegal,'” Hadi said.

The case of large bumble bee kill in the state of Oregon underscores the importance of following the label direction closely. Always read the entire label to get the full information of the usage and potential restrictions of the product at hand.

Hadi said it is important to recognize the different languages in pesticide labels pertaining to bee toxicity. The examples in figures 1 and 2 serve as illustrations.

“In both pesticide products, the labels stated ‘high toxicity’ on bees. In figure 1, the label proceeds with the direction not to apply the product if bees are visiting the treatment area. In figure 2, the product is not to be applied while bees are actively visiting the treatment area. The subtle difference between ‘visiting’ and ‘actively visiting’ has quite a large significance,” he said.

In this case both pesticides are toxic to bees but, Hadi explained, the pesticide in figure 1 has an extended residual toxicity compared to the pesticide in figure 2. Consequently, the product in figure 1 has a longer toxic period against bees compared to the one in figure 2.

“The phrase “do not apply if bees are visiting,” in figure 1 signifies the product’s potential to kill bees by residual effect. In this case, bees visiting treated areas later during the day can still be fatally affected by the product,'” Hadi said. “In the case of the product in figure 2, the phrase ‘do not apply while bees are actively visiting’ signifies the product’s potential to kill bees in the case of direct exposure.”

Practically speaking, Hadi said the product in figure 2 should not be used when the bees are visibly foraging in the field.

“During crops’ blooming period it is recommended to use pesticides with label language illustrated in figure 2,” he said.

Keeping in mind, Hadi said, that application of the product in figure 2 should be conducted after the active foraging time for bee is completed – for example in the late afternoon or in the evening.

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