By Ashely Minnerath and Mace Vaughan
It’s summer and organic farmers across the U.S. are in the thick of managing weeds and pests. Right now, many of you are getting ready to till out crabgrass, treating crops to control flea beetles or squash bugs, or maybe wishing you had chosen a different cover crop or crop rotation. When making decisions about these management practices, you have the ability to dramatically affect – for better or worse – populations of beneficial insects that play pivotal roles in crop pollination and pest management. By understanding some basic principles of native bee biology, nesting habits, and the toxicity of various organic-approved pesticides, farmers can balance crop management strategies with the needs of resident wild bees and other beneficial insects.
Organic does not mean benign
Insecticides are usually harmful to beneficial insects and their use should be minimized whenever possible. Even some organic-approved pesticides can have devastating effects on native bees. To reduce these negative effects make sure that your Integrated Pest Management plan incorporates the habitat needs of pollinators.
When insecticides can’t be avoided, choose the least toxic option available. By properly calibrating equipment, using the most targeted spray equipment, and spraying during appropriate weather conditions, farmers can reduce the risk of pesticides or pesticide drift to resident bee populations.
A few tips:
- Avoid spraying when crops, adjacent flowering weeds, or cover crops are in bloom.
- Choose liquid formulations over dusts, as the dusts are long-acting and can become trapped in the pollen-collecting hairs of bees.
- Be aware of the commonly used organic pesticides that are particularly harmful to native bees (pyrethrins, Rotenone, Beauveria bassiana , and spinosad).
Harnessing beneficials
Native bees and the natural enemies of crop pests need access to pollen and nectar-rich floral resources throughout the growing season in order to thrive. There are many ways to adjust current farm management practices to increase the forage available on your farm. For example, when developing cropping systems or rotations, consider how you can maximize the diversity of bee-pollinated crops in order to provide more abundant forage opportunities throughout the season.
Similarly, it is useful to think beyond one year. You may have an abundance of pumpkin or sunflower in one year, and be building up a population of wild bees near that crop. However, if the next year those crops are not available within the foraging range (say 750 feet) of where the offspring of those bees emerge, they will not continue to increase in number. Cover crops are frequently used to build soil tilth and fertility and control weeds. Choosing bee-friendly flowering cover crops, such as lacy phacelia, buckwheat, clover, or alfalfa, and allowing these cover crops to bloom, provides additional nectar and pollen resources.
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