GAINESVILLE, Fla. – Years ago, when purchasing a flat of pansies at a garden center, Chris Wilson noticed a label indicating the flowers had been treated with insecticides.
“I remember thinking to myself, ‘But bees can’t read labels,’” said Wilson, interim chair of the UF/IFAS soil, water and ecosystem sciences department.
That thought inspired Wilson’s current research project, a joint effort with his wife, professor Sandra Wilson of the UF/IFAS environmental horticulture department.
Combining Chris Wilson’s expertise in environmental chemistry and toxicology and Sandra Wilson’s in plant physiology and horticulture, they decided to explore the relationship between pesticide management practices, plants and pollinators.
Funded by a $750,000 grant from the USDA National Institute of Food and Agriculture, the Wilsons are working to minimize pollinator exposure to toxic concentrations of insecticides commonly used in the country’s $21.08 billion ornamental horticulture industry.
Pollinators like bees, butterflies and hummingbirds depend on flowering plants for nectar and pollen, but these food sources could become contaminated by some types of pesticides used to protect the plants from harmful pests and diseases.
Ingestion or contact with harmful pesticides can cause behavioral changes in insect pollinators, including disorientation, tremors and poor reproduction. The effects can also be lethal.
“Pollinators, which we are trying to support by planting flowering ornamentals, may be unintentionally harmed by our efforts to help them,” said Sandra Wilson.
One of the key goals of the Wilsons’ project is to understand how pesticide application decisions influence contamination of nectar and pollen and to then develop guidance for growers to minimize the likelihood of sending plants to market that may present high risks to pollinators.
Through this research, “we are hoping to find a middle ground for pesticide applications in ornamental container plant production and protection of pollinators from exposures,” said Vanesa Rostán, a doctoral student in the UF/IFAS soil, water, and ecosystem sciences department who is working with the Wilsons.
Early tests examined concentrations of thiamethoxam, a broad-spectrum, systemic insecticide, in the nectar of Indigo Spires salvia and showed method, rate and timing of pesticide application are significantly influential.
Low-rate applications of thiamethoxam yielded some of the starkest results.
In plants that had yet to bloom, drenching the soil with the pesticide led to concentrations that were 117 times higher than spraying the pesticide.
In plants that had bloomed, drenching led to concentrations that were 55 times higher than spraying.
“I was initially expecting that spray-applied pesticides would result in higher concentrations because that technique applies the pesticide right where the flowers are,” Chris Wilson said. “But drenching resulted in concentrations that were orders of magnitude higher. For me, that was eye-opening.”
When the Wilsons studied thiamethoxam’s effect on lantana nectar as part of a second, not yet-published study, they found that spraying it on the plants didn’t result in detectable concentrations in most cases.
Drench applications, however, resulted in increasingly higher concentrations as the rate increased and the flower buds matured.
“The lack of detectable sprayed pesticide found in nectar came as a surprise, but the woody texture of lantana leaves may prevent absorption,” said Mia Cabrera, a UF/IFAS graduate student in environmental horticulture working on the project.
In addition to publishing their research, the Wilsons and the students plan to share results with growers through future workshops and informational videos.
Ultimately, they would like to work with the ornamental industry to develop best management practices for pesticide application and pollinator protection.