Skip to main content

Midsummer Management of Crop Pests and Pollinators

By Ashely Minnerath and Mace Vaughan on 3. August 2023
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 pesticides, farmers can balance crop management strategies with the needs of resident wild bees and other beneficial insects.


Reduce your pesticide use through prevention 

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. We encourage home gardeners to take the Bring Back the Pollinators pledge to avoid pesticides in yards and gardens and provide safe, pesticide-free habitat for pollinators.

For farmers, putting pollinators first starts with an Integrated Pest Management plan that includes careful scouting and monitoring for pests and diseases. Just like in medicine, a good diagnosis is needed before deciding on a treatment. Often, pest and disease issues can be kept within manageable levels with basic prevention practices that interrupt pest and disease life cycles, like sanitation, pruning, crop rotation, and planting resistant varieties.

When insecticides can’t be avoided, take steps to minimize the risks to pollinators and other beneficial insects. By properly calibrating and using the most targeted equipment, treating only the area needed,, and spraying during appropriate weather conditions, farmers can reduce the risk of pesticides or pesticide drift to resident bee or other beneficial insect populations and their habitat.

A few tips:

  • Avoid spraying when crops, adjacent flowering plants (including weeds), or cover crops are in bloom. Beneficial insects can receive harmful levels of pesticides from contact with sprays as well as from residues in and on pollinator-friendly flowers and host plants.

  • Only spray when weather conditions are optimal to minimize drift. Windy conditions during pesticide applications can cause sprays to drift into nearby habitat. Keep an eye out for signs of temperature inversions (e.g., surface dew, low-hanging fog, no to low wind), as long-range drift of small droplets can also occur during these conditions.

  • Choose less toxic pesticides and formulations wherever possible. Tools like the Bee Precaution Pesticide Ratings can help farmers compare toxicity of different pesticides to bees. Dusts tend to be more hazardous than liquid formulations, as 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 harmful to native bees (including spinosad, pyrethrins, and Beauveria bassiana). For more on the toxicity of organic-approved pesticides, see our factsheet.


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 mustard, and allowing these cover crops to bloom, provides additional nectar and pollen resources.


lacey phacelia
This bumble bee is benefiting from the blooms of lacey phacelia used as a cover crop at Vilicus Farms in Havre, MT. (Photo: Jennifer Hopwood / Xerces Society.) 


Allowing weeds – only species that aren’t noxious or hosts for pest insects – to flower along field edges, roads, or irrigation ditches can also provide a food source for beneficial insects. Similarly, consider allowing some un-harvested crops to bolt before plowing them under. When combined, all of these practices can
increase the floral resources available on your farm.


Look down!

Approximately 70% of native North American bees nest in tunnels under the ground, and abundant populations have been documented nesting in sunflower and pumpkin fields, and under orchards. When deep tillage is employed to manage field weeds, ground nests and developing bee larvae can be destroyed. This is particularly relevant for farmers who grow crops in the squash family (cucurbits).

Squash bees in the genus Peponapois have coevolved with cucurbit plants and almost exclusively visit their flowers. These bees tend to nest at the base of the squash plant, between 6 and 12 inches below the ground. Farmers who discover squash bees living in their squash and melon fields could take steps to protect them by plowing at shallower depths (less than 6 in) or investigating the use of no-till options.

Similarly, using mulch such as plastic, woodchips, and straw can limit nesting opportunities and inhibit bees from emerging from their nests. Although, we have seen squash bees nesting happily under pumpkin plants growing in plastic mulch where the holes cut in the plastic were at least 1 square foot in size, and even a short way under the plastic.


squash bee
Squash bees nest in the ground where Cucurbit crops are grown. Tilling practices may negatively impact the abundance of these specialist pollinators.


These options may not be practical for every farm operation. However, by paying close attention to the natural rhythm of your farmscape and noting the effect that various farm practices have on resident beneficial insects, attracting and protecting pollinator populations can increase not only a farm’s sustainability, but its productivity, too.



This article originally appeared in the Summer 2014 issue of Rodale Institute’s New FarmNew Farm is a quarterly publication given to members of Rodale Institute’s Organic Farmers Association


Mace has led Xerces’ Pollinator Conservation Program since 2003 and acted as Joint Pollinator Conservation Specialist to the NRCS since 2008. In his tenure at the Xerces Society, the pollinator program has grown from a small pilot project on California farms to a national program implementing pollinator conservation projects across the US. Mace has written numerous articles on the conservation of bees, butterflies, aquatic invertebrates, and insects, and is co-author of the publications Attracting Native Pollinators: Protecting North America’s Bees and Butterflies, Farming with Native Beneficial Insects, and the Pollinator Conservation Handbook. He is the lead author of Farming for Bees: Guidelines for Providing Native Bee Habitat on Farms. He was a lecturer on honey bee biology and beekeeping at Cornell University, from which he holds Masters Degrees in Entomology and Teaching. Mace has conducted research into the behavior and community ecology of insects, and has worked as an insect wrangler and bee expert for PBS Nature. 

Your Support Makes a Difference!

Xerces’ conservation work is powered by our donors. Your tax-deductible donation will help us to protect the life that sustains us.