University of Florida researchers are investigating ways to minimize pollinator exposure to insecticides commonly used in the ornamental horticulture industry.
Funded by a USDA National Institute of Food and Agriculture grant, the husband-and-wife team of Drs. Chris and Sandra Wilson is studying how pesticide management practices affect both plants and the pollinators that depend on them. Both researchers are faculty members in the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFAS).
Pollinators such as bees, butterflies, and hummingbirds rely on flowering plants for nectar and pollen. However, these food sources can become contaminated by certain pesticides used to protect plants from pests and diseases. Exposure—whether through ingestion or physical contact—can cause behavioral changes in insect pollinators, including disorientation, tremors, and reduced reproductive success. In some cases, the effects can 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.
A major goal of the Wilsons’ project is to understand how pesticide application decisions influence contamination levels in nectar and pollen. This knowledge will help them create guidance for growers to reduce the chances of sending plants to market that may pose high risks to pollinators.
Their research aims to identify a balanced approach—one that maintains effective pesticide protection in ornamental container plant production while minimizing pollinator exposure.
Early tests examined concentrations of a broad-spectrum, systemic insecticide found in the nectar of Indigo Spires salvia. Their findings show that pesticide application method, rate, and timing all play significant roles in contamination levels.
Some of the most striking results came from low-rate pesticide applications. In plants that had not yet bloomed, drenching the soil with the pesticide produced concentrations 117 times higher than spraying. In plants that had already bloomed, drenching produced concentrations 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 the pesticide’s effect on lantana nectar, they found that spraying the plants did not produce detectable concentrations in most cases. Drench applications, however, resulted in increasingly higher concentrations as application rates increased and flower buds matured.
In addition to publishing their research, the Wilsons are sharing their findings with growers through future workshops and informational videos. Their long-term goal is to collaborate with the ornamental industry to develop best management practices for pesticide application and pollinator protection.
Top image credit: Environmental horticulture professor Sandra Wilson, from left, doctoral student Vanesa Rostán and Chris Wilson, interim chair of the UF/IFAS soil, water and ecosystem sciences department. (Tyler Jones, UF/IFAS)