Issue 2, May 5, 2020
Protecting Pollinators When Using Pesticides
Spring is a time for pollinators like honeybees, native bees, hummingbirds, butterflies and moths to begin to visit our landscape flowers. At the same time, we also have nuisance pests emerging. In order to allow pollinators to continue to do their job and to control pests we should consider a few recommendations to help conserve the beneficials.
Choose the least toxic, less persistent pesticide whenever possible to minimize risk to pollinators. Choose pesticide products that have active ingredients that are the least harmful to bees. An active ingredient is the chemical in a pesticide that controls the target pest. It is common to find the same active ingredient under a variety of different trade names. More information about active ingredients can be found by talking with educators at your local Extension office, reading online Extension materials, like this one from Oregon State University that also has an accompanying app for you phone https://catalog.extension.oregonstate.edu/pnw591 and visiting the National Pesticide Information Center website.
Always read the pesticide label carefully. Under the environmental hazards section of the label, note any bee hazard and other environmental warnings. Some products used by gardeners may not contain a bee hazard warning even if the product is highly toxic to bees, because the location for use listed on the label may not be attractive to bees. Ensure that the site and the type of plant that you intend to treat does appear on the pesticide label. For instance, do not use an insecticide labeled for houseplants on a cucumber plant in the garden.
Make targeted applications. Scout for pests regularly and selectively treat pest problems, avoiding blanket applications to the landscape. Take action while pest numbers are low and manageable in order to use the least amount of pesticide. Do not over apply the pesticide, since more is not necessarily better. Follow label directions and use only the amount indicated.
Consider the host plant. Does it attract bees or other pollinators? Some plants are extremely attractive to pollinators while in bloom, such as crabapple trees. Certain plants might not have flowers that are easily recognized or visible from the ground. For instance, black gum trees have flowers that are very attractive to bees, yet inconspicuous to us. While turfgrass is not attractive to bees, many flowering weeds found in lawns do attract bees, such as clover and dandelion. Mow the lawn to remove the flowers prior to treating a lawn with pesticides.
Avoid applying pesticides to plants during flowering. Do not apply insecticides that are highly toxic to bees to plants any time during flowering. The risk to pollinators is too great. If applying an insecticide is necessary, choose the least toxic product and plan to apply it well before or after the plants flower. Avoid applying systemic neonicotinoid insecticides to the soil around bee-attractive plants any time before bloom in the spring. Wait until the petals have dropped or use a bee-friendly product. Consider using an alternate control tactic such as removing pests manually, i.e., removing tents with tent caterpillars.
Consider the formulation. The formulation of a pesticide is the way that the active ingredient is packaged, such as a dry powder, liquid, granule, etc. Typically, dry granular formulations are the least hazardous to bees. Soil-applied granules or liquids are not a direct contact hazard, but some soil-applied insecticides are systemic and may persist at low concentrations in pollen and nectar when applied to blooming plants.
Foliar sprays provide risk from both direct contact and residues on the plant. Foliar insecticides include both short- or long-term residual materials, so contact injury may still be possible for days after treatment with the long-term residual materials.
The most hazardous formulations are dusts and microencapsulated formulations because their particles are small enough to stick to bee hairs in the same manner as pollen. Bees may pick up particles and carry them back to the hive, resulting in toxic effects on the colony. Insecticidal dusts applied to flowers can be very hazardous to bees for this reason.
Locate nearby beehives and maintain a buffer between any beehives and your treatment area. Visit beecheck.org to locate apiaries nearby.
Prevent drift. Do not spray on windy days in order to help prevent pesticide drift to non-target weeds, wildflowers, and other flowering plants. Bees inevitably travel to blooms of plants around home gardens, orchards, and fields, so they can easily be affected by pesticide residues and drift. Ensure that the pesticide does not drift to water sources, including puddles where pollinators may drink. Use a coarse spray with larger droplets and keep the nozzle as low to the ground as possible to prevent drift.
Apply pesticides at a time of day when bees are not active. If you choose a moderately toxic material with short-term residual activity, apply the product in the late evening when bees are not actively foraging. Honey bees forage during the day and will likely contact the pesticide if it is on the blossoms. Honey bees are generally inactive one hour after sunset until two hours before sunrise. However, unusually warm weather encourages bees to forage both earlier and later in the day.
Consider bees when treating landscapes for nuisance insects like mosquitoes and ticks. Avoid harm to pollinators resulting from mosquito spraying or perimeter treatments for other nuisance insects by avoiding treating blooming plants. These kinds of applications may cover a large portion of the landscape. If an insecticide is necessary, use insecticides with a very short residual and/or low toxicity to bees when possible, and do not apply when bees are active during the day.
Do not apply pesticides before rain or if the forecast predicts heavy dew in order to help prevent contamination of water and soil. Consider nearby waterways such as streams, ditches, or ponds, and do not apply pesticides close to the water’s edge.
Adapted and Permission to use- granted by author- Mary Ann Rose, director, Pesticide Safety Education Program https://ohioline.osu.edu/factsheet/anr-68
Author:
Maria Turner