Protecting Pollinators

In recent years, protecting declining populations of pollinators has become an important issue. Many of our vegetable crops are dependent upon pollinators for production of fruit. Below is a table that highlights the benefits of honey bees and other pollinators for vegetable production.

 

Crops That Require Pollinators Crops That Don’t Require Pollinators But Have Better Yields with Them Crops From Which Pollinators Collect Pollen
melons eggplant pea
cucumber lima bean snap bean
squash/pumpkin okra sweet corn
pepper tomato

Table 1. The importance of pollinators in selected vegetable crop production.

There are a number of stresses that harm pollinator populations. Pesticides, although not the most important, are one factor that vegetable growers have some control over. Here are some of the ways that vegetable growers can impact pollinators with pesticides.

  • Applicators apply insecticides to vegetables when pollinators are present, resulting in direct exposure. This can be true for crops that require pollination services and for crops where pollinators are only feeding on pollen.
  • Applicators apply insecticides to vegetables when pollinators are not present, but the insecticide residues persist enough to potentially harm pollinators when they visit the crop.
  • Applicators apply systemic insecticides to vegetables. These products move through the plant to flowers in quantities that could harm pollinators.
  • Applicators apply insecticides outside the vegetable production field that move (in some manner) into the field in sufficient quantities to harm pollinators.
  • The residues of systemic insecticides remain in the soil from a previous crop. The vegetable crop then takes up the insecticide, which moves to flowers in quantities large enough to harm pollinators.

There are a number of steps that vegetable growers can use to protect pollinators.

  1. Read and Follow Insecticide Labels

Insecticide labels contain specific instructions to help you reduce risks. All insecticides that are toxic to bees have warnings on the label. These warnings are often hard to find on some older insecticide labels. However, many newer insecticides have special bee icons on their labels that draw attention to the potential for harm to pollinators. They often have specific instructions for

  1. Follow IPM Principles

Integrated Pest Management (IPM) is a system that combines different methods to keep pest populations low while allowing for profitable production and minimizing adverse environmental effects. To reduce the risk of harming pollinators, IPM principles guide producers to take advantage of non-insecticidal practices that can reduce pest damage. For example, you might rotate crops to control Colorado potato beetle control or plant sweet corn early to avoid corn earworm.

When deciding whether to apply an insecticide, determine whether the net profit from applying the insecticide is greater than the cost of applying it. Making an informed decision usually involves scouting your field or orchard to determine the level of pests that are present. It doesn’t make good sense to spend $50 per acre to avoid $30 per acre in losses. Using IPM principles will often reduce the amount of insecticides you need to apply.

  1. Register with DriftWatch

The DriftWatch website (driftwatch.org) is a place where specialty crop producers can register their production sites on a map. Pesticide applicators can access this data before applying anything to nearby fields. The rationale behind this site is to provide applicators with the locations of sensitive sites, so they can take precautions to avoid overspray or drift to locations where they are not wanted.

  1. Don’t Treat Areas Where Pollinators Visit

Some crops, like cantaloupe, bloom throughout the growing season. If melon growers stopped applying insecticides when the first flowers appeared, striped cucumber beetles would feed unabated and likely vector the bacterium that causes bacterial wilt of cucurbits to a large percentage of the plants in the field.

However, a muskmelon flower only opens for one day and it closes in the late afternoon. This means pollinators are unlikely to be in fields after the flowers have closed. This knowledge provides melon growers an opportunity to spray their fields with an insecticide in the late evening without harming pollinators. However, growers still need to use a non-systemic insecticide so that the residue will only be on the outside of the new flowers that open the next day. In that way pollinators will not contact the insecticide and no harm will ensue.

Growers should also remember that pollinators will be attracted to dandelions and other blooming weeds even if the crop is not in bloom. Applying insecticides when weeds are in bloom can also potentially harm pollinators.

  1. Avoid Seeds Treated with Neonicotinoids

Some vegetable seeds are sold with a coating of a neonicotinoid insecticide, usually thiamethoxam. If you direct-seeding a crop (such as pumpkins), the insecticide in the seed coating will control insects such as aphids and striped cucumber beetles for up to three weeks. However, because neonicotinoids are systemic insecticides, they move into the flowers and will be present in the pollen in levels that could harm pollinators.

If you grow transplants in a greenhouse for four or five weeks before planting them in the field, the insecticide from a coated seed will not control any insect pest in the field, but harmful residues may be present in the pollen, which would harm pollinators.

Growers who are direct-seeding crops may decide that the insect control treated seed provides outweighs the potential harm to pollinators based on field history. However, growers who are transplanting crops will receive no benefit from seeds insecticide-treated with insecticides but still risk harming pollinators. If you are planning transplant production, request seeds with no insecticide treatment from your seed dealer.

  1. Use Low Rates for Neonicotinoid Soil Drenches

Some growers of cucurbits and other crops apply a neonicotinoid insecticide (Admire Pro® or Platinum®) at planting. Like the seed treatments, these applications provide about three weeks of insect control. Never use a soil drench insecticide if you also have seed treated with a neonicotinoid. The combination will not improve insect control.

Research has shown that soil drench applications at the low end of the label range provide control equal to applications at the highest label rates. However, the lower rates reduce (but don’t eliminate) residues in the pollen. Although both rates produce residue levels in the pollen that could cause harm, the lower rate is less likely to cause a problem.

  1. Communicate with Your Bee Provider

If you rent bees to pollinate your crops, be sure to talk with your beekeeper about the pests that you have to deal with and the need for any insecticides you may apply. Coordinate the arrival and departure of the bees with your insecticide applications to ensure minimize any potential harm to the bees.

Pollinators, both domesticated and feral, are important to the production of many vegetables. By following these few suggestions, vegetable growers can do their part to preserve the health of all of our pollinators, as well as maintain the goodwill of beekeepers.

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