Of pesticides and pollinators

Mind The Blossoms

by Nicole Galland

Mind The Blossoms

Genevieve Jacobs

The application of pesticides—organic or not—on plants in bloom, can harm important pollinators like bees.  

Everyone loves a good fruit-bearing plant. Even pests. Gardeners and farmers who cultivate squash, melons, blueberries, fruit trees, tomatoes, and other food crops tend to use some form of pesticides so their treasured harvest can ripen in peace. The right kinds of pesticides to use on food crops is a hot-button topic, and not our concern today. Whether you are using straight DEET or the mildest organic brew to keep the pests away, all pesticide should be applied mindfully of pollinators’ cycles. Otherwise, there will be health risks not only to the human consumers of the fruit, but to the industrious, benevolent critters who make sure we have fruit in the first place: bees.

Bees of all varieties—honey, wild, or chard, mason, bumble, or nearly 3500 other American varieties—will suffer if pesticides are applied to open blossoms. So the golden rule regarding pesticide is: don’t apply it when a field (or even an individual plant) is in flower. Some farmers claim it is safe to apply short-residual pesticide to blooming plants in the evening, but that transfers the danger to nocturnal pollinators: moths, bats, and even some species of bees. Play it safe: don’t apply pesticide when your plants are in bloom, period.

In fact, to be really responsible, don’t apply pesticides to your plants when any nearby crops or even wild flowering plants are in bloom. This is especially true if the fauna include milkweed or dandelion, both of which bees love. Pesticide does not stay put—it moves around, and if it lands on a blossom, it could end up on a bee.

To further minimize the danger of drift to bees who are working in areas surrounding or in your garden or field, do not apply pesticide when the wind is blowing more than 10 mph.

Use granules instead of dust formulations and avoid “micro-encapsulated” pesticides, which resemble pollen and are more likely to attract a bee’s interest. Also, avoid “wettable powder” and “flowable” formulations, as these concoctions dry to a dust-like consistency which—like dust and micro-encapsulates—can be carried back to the hive via foragers, thereby endangering the entire hive, not just the bees in the field.

If you absolutely must use a pesticide that poses any danger to honey bees, and you live within two miles of a beehive (or, if you are truly conscientious, within five miles of one), notify the beekeeper a few days in advance that you will be applying pesticide. Given the profusion of small apiaries on the Island, chances are you are near one; use this as an opportunity to get to know your local keepers.

Another thing to keep in mind is temperature. If the mercury dips considerably below normal in an evening, do not apply pesticides that night, as the cool air slows the degradation process of toxic chemicals, and the following day bees will be at greater risk. On the other hand, bees will forage more when the weather is considerably above average, so that’s not a good time to apply pesticide, either.

In short: it is best to apply pesticide well before or after the blooming period, on a still evening night when the temperature is close to normal.

Protecting pollinators is enlightened self-interest. Bee colonies are being devastated by disease, mites and other factors; the more we do to help our four-winged friends, the more they will be able to pollinate the plants that give us our harvests.

Editor’s Note: See EV#3 ‘Island Queens’ for more about this relationship between pollination and local sustainable agriculture.