Minimizing Bee Exposure to Pesticides on Fruit Crops

Published: April 28, 2021

Bees are essential for successful pollination of many fruit crops, including apple, pear, Japanese plums, sweet cherries, blueberry and elderberry. Because bees transfer pollen from flowers of one fruit tree to blossoms of another to initiate the process of pollination and subsequent fruit set, it is important to protect them during the bloom period (Figure 1). Honey bees, as well as native bees and other beneficial insects, are vulnerable to some of the pesticides used to control insects, diseases, and weeds. When foraging bees bring pollen back to a hive from flowers treated with a pesticide, it is fed to the brood and can be toxic.

Figure 1 A bee foraging for pollen on an apple blossom at an ideal time for avoiding the use of an insecticide.

There are several easy precautions that can be taken to protect bees. The selection of pest-resistant cultivars is one way to reduce the need for pesticide use. For example, apple cultivars, such as Liberty or Enterprise, have resistance to some of the major diseases (fire blight, scab, and cedar apple rust) that infect apples. Thus, these sprays for these diseases can be eliminated from a pest management program. Also, scouting for pests on a weekly basis is useful to determine the presence and severity of the pest. Usually, the application of a pesticide is only necessary when it is severe enough to severely reduce fruit yield or the longevity of the tree is threatened. Thus, scouting is useful to determine when to take action to control problematic insects or diseases.

Another way to prevent bee exposure to harmful products is to avoid the use of insecticides or miticides during the bloom period of fruit trees and plants. If a pesticide application during bloom is necessary, read the product label carefully. Avoid the use of pesticides that have caution statements on the label, such as "highly toxic to bees" or "extended residual toxicity". Products with long residual times may be toxic to bees for a week or more. Also, avoid applying pesticides when bees are active. Honey bees are generally active between two hours before sunrise and one hour after sunset, although they may forage earlier and later in unusually warm weather.

If possible, try to minimize the application of fungicides during bloom. Some insecticides have a synergistic effect on bees when tank-mixed with a fungicide and may become more toxic to bees than when either product is used alone. If a fungicide is necessary during the pollination period, avoid the use of products containing captan, ziram, or iprodione as these fungicides can affect brood development. Also, when necessary, apply fungicides when bees are generally less active. Also, limit or avoid the use of products that recommend the addition of adjuvants or surfactants to the tank-mix of the pesticide when possible. Although not thoroughly investigated, it has been suggested that some adjuvants and surfactants enhance the penetration of pesticides through the bee's outer cuticle.

Another way to prevent exposure of bees to pesticides is to eliminate blooming weeds near fruit trees, such as dandelions, which attract bees. If weeds can't be entirely eliminated, clipping or mowing their blooms before applying pesticides will make them less attractive to bees. Alternatively, self-pollinating fruit trees and plants can be grown to reduce the need for bees. For example, peaches, nectarines, sour cherries, apricots, European (blue) plums, grape, strawberry, blackberry, raspberry, and gooseberries do not solely require pollinators for fruit set, even though fruiting is enhanced by bee activity during the bloom period. Thus, these types of fruits can be planted to minimize the reliance on bees for pollination.

For more information, refer to MU Guide Pollinating Fruit Crops (missouri.edu).

To learn more about protecting pollinators, including honey bees, native bees, butterflies, flies, beetles, birds and bats, consider participating in the Missouri Master Pollinator Steward program. This program provides information on the protection of our food supply by supporting healthy ecosystems. For more information, visit https://extension.missouri.edu/programs/master-pollinator-steward.