January is an unlikely time to give much thought to bees, but they’ll be back in a few short months and honey bee numbers are declining. According to Iowa State University Extension, no one factor is believed to be the cause of bee losses; rather it appears to be a combination of problems such as habitat loss, poor diet, parasites and pesticide exposure. By design pesticides are toxic to insects and that includes honey bees. Honey bees, bumble bees and native solitary bees are several varieties that are susceptible to pesticides. As a home gardener, you can plan to take steps to reduce your use of pesticides this growing season and help protect pollinators.
Neonicotinoids are a group of insecticides that have been under research and greater scrutiny as harmful to bees. This group includes Imidacloprid, which is the most widely available insecticide for use in the home garden. Other active ingredients in the neonicotinoid group include acetamiprid, clothianidin, dinotefuran, thiacloprid and thiamethoxam. To determine if you are using products with these active ingredients, read labels thoroughly. Insecticide labels list the percentage of the active ingredient and what that ingredient is called.
This particular group of insecticides are a relatively new type of insecticide that is systemic. Systemic means that the insecticide spreads throughout the plant in plant tissues, including pollen and nectar. They stay in the ecosystem for a long time and they are highly toxic to bees. Interestingly enough, insecticides can have a negative impact on bees even if it doesn’t kill them by affecting a bee’s ability to fly, navigate and reproduce.
The harm of insecticides to bees varies with the plant, time of year, and time of application. Treating anything when in bloom (or just before bloom) is extremely dangerous to pollinators.
To lessen harm to pollinators, make sure you are a good steward of integrated pest management, meaning first evaluate if a pesticide is necessary. If damage is cosmetic and already is done to a plant, an insecticide application will not improve that plant’s health or appearance. If an insecticide is needed, read the label to see if the product is toxic to bees. Formulas such as granules and emulsifiable concentrates are safer to pollinators than those that are wet or powder. Avoid insecticides toxic to bees and use insecticidal soaps or try a product called Bacillus thuringiensis (a natural bacterial disease to insects) and don’t use systemic insecticides on blooming plants if they last for an entire year. For more information and tips on the use of insecticides , visit www.extension.iastate.edu and look for “Protecting Bees from Pesticides SP455,” that can be downloaded for free.
For questions about bees, pesticides and other gardening issues, call the Linn County Extension Hortline at (319) 447-0647.
Lisa Slattery is an Iowa State University Extension Linn County Master Gardener