Credit: Dr. Nigel Ryan / University of Guelph
A new University of Guelph study reveals that an insecticide used to control pest infestations on pumpkins and gourds significantly impedes the reproduction of bees that nest on the ground – valuable pollinators for many food crops.
This first-of-its-kind study of pesticide effects on land-nesting bees in a real-world context found that white squash bees exposed to imidacloprid dug 85 percent fewer nests, collected the least pollen from crop flowers and produced 89 percent fewer offspring than non-exposed. Bees.
“Because they don’t make nests and don’t collect pollen, they can’t raise offspring,” said Dr. Susan Willis Chan, a postdoctoral researcher at the School of Environmental Sciences (SES), who conducted the study with Dr. Nigel Ryan. Holder of the Rebanks Family Chair in SES Pollinator Conservation. “This means that the population exposed to imidacloprid will decrease.”
Neonicotinoids (or neonicides) are neurotoxic insecticides that kill insects by attacking their nervous systems, affecting learning, foraging and navigation in many species of bees. Farmers use neonic imidacloprid to control cucumber beetles, which are the most damaging crop pests of squash and squash.
Many species of land-nesting bees, including pumpkin bees, are responsible for pollinating many fruits, vegetables and oilseed crops in North America, Chan said.
Single bees that nest on the ground make up about 70 percent of the bee species. It is a really important environmental group and it is also really important in pollinating crops. “
However, these terrestrial dwellers are often overlooked when it comes to assessing the effects of pesticides on pollinators.
It was recently published in Scientific Reports In the study, there were three years of observing foraging and nesting behavior of pumpkin bees.
To mimic field conditions, Chan kept bees in net-covered containers that still allow exposure to sun, rain and other environmental factors. Pesticides were used in ways that reflect the actual use in farmers’ fields.
Chan tested three insecticide treatments: the neon imidacloprid applied to the soil at the time of planting; the neonic thiamethoxam applied as a seed treatment; An anthranilic insecticide (a non-neon emerging insecticide) is sprayed on growing plants. The fourth group used no pesticides as a control.
A three-year bee study allowed the team to demonstrate the long-term effects of imidacloprid exposure on reducing nest building, foraging and progeny control.
Bees visiting squash plants treated with anthranilic thamide collected less pollen than those in the control group but had no fewer nests or offspring. Chan did not see any measurable effects from thiamethoxam seed treatment on pollen harvest, nest building, or offspring production.
“Farmers and regulators need to find alternatives to applying imidacloprid to soil for pest control on gourds and gourds,” she said.
“My recommendation for pumpkin and gourd growers to stay away from soil-applied imidacloprid to keep pumpkin bees healthy.”
Other solitary, land-nesting species are also likely to be affected, Raine said.
Noting that other organisms that live on land live in agricultural fields, he said, “The type of effects resulting from exposure to pesticides applied to soil that we saw in this study could affect many other species of wild bees.”
He said current regulatory assessments of insect pollinators fail to consider the risks associated with pesticide residues in the soil. “Our results highlight why this must be changed to better characterize the risks for the many species of bees that spend a large portion of their lives in the soil.”
Given the importance of insect pollination in crop production, Chan said, “Farmers need to protect their crops from pests, but they also urgently need to protect pollinators from the unintended effects of pesticides.”
Referring to imidacloprid, she said, “The data for this particular product is so clear that there is really no doubt about what needs to happen. We have to find something else.”
This research was funded by the Ontario Ministry of Agriculture, Food, and Rural Affairs; Ontario Department of Environment, Conservation and Parks; Ontario Fresh Vegetable Producers Association; The Council for Natural Sciences and Engineering Research; The Weston Family Foundation.
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