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Managing Crops and Bee

University of Minnesota Extension, Stearns County News
July 27, 2013         
Source:  Dan Martens, Extension Educator
University of Minnesota Extension
Stearns, Benton & Morrison Counties


Managing Crops and Bee
By Dan Martens, University of Minnesota Extension

FOLEY, Minn. (07/25/2017) — I’ve written recently about some insect problems that crop farmers and agronomy advisors are scouting for in fields from mid to late summer – specifically about soybean aphids, thistle caterpillars, European corn borer, and corn rootworms. I focused primarily on the farmers’ task to protect their crops for their need to make a living, and our need for food, energy and other byproducts.

I appreciated a call from a central Minnesota beekeeper recently, who had some concerns about how much spraying might be done this year yet, and how that might affect bees. At this point he was particularly concerned about thistle caterpillar spraying, and also about spraying for soybean aphids.

We are seeing a lot of Painted Lady Butterflies this summer, the adult stage of the thistle caterpillar. We have also been seeing thistle caterpillar larvae feeding on soybean leaves. There could be a second hatch of larvae and perhaps a second round of scouting and spray decisions for soybeans.

The concern for bees, is that spraying might be done to protect soybeans from insect damage while bees might be foraging in soybeans that are blooming. I’ve learn that soybeans are not a favorite crop for bees, but that doesn’t mean they are not in fields.

People who make a significant part of their living by growing crops, and others by producing honey, seem sometimes to be at odds with each other. They both face significant challenges in today’s markets and conditions to make ends meet. Most of us care quite a bit about our hobbies too. In more ways than we realize, in many avenues of life, we depend on each other. 

One U of M reference says honey bees and native bees, such as bumble bees, pollinate 30% of the plants that produce the vegetables, fruits, and nuts that we consume. MN Dept. Ag information says Minnesota usually ranks in the top 5 states in honey production. Minnesota beekeepers also move many colonies to California and several southern states for pollination and over wintering. Many beekeepers winter bees in Minnesota. Minnesota is also a very significant agriculture producer.

You might think about bees that forage on plants and produce honey, and pollinate other crops. Dairy cows forage on plants and produce milk for a large variety of dairy foods. Someone might point out that it’s easier to manage where cows are eating.

MDA has a web based process that allows bee keepers and farmers to register, so they can work together. It’s good to meet your neighbors. MDA has drift watch and bee watch program for investigating unusual bee death situations and other issues. For farmers, the key to protecting against liability, is to follow label directions based on research based thresholds. Many insecticides now have specific recommendations for reducing risk to bees. For more information from MDA, do a website search “MN Dept. of Ag Bees” or call 1-800-967-2474.

The FIRST STEP to reducing risk for pollinators and other beneficial insects it to follow research based thresholds for making treatment decisions. Farmers really can’t afford to spray when there is NOT a credible risk for economically significant damage to the crop.

The SECOND is to choose a product that has less risk for bees, based on label information, in the context of what will do a good job for the insect damaging the crop. The THIRD is to follow the label.

Some other strategies to consider for reducing risk to bees include:
1. Spray in the evening or night time.
2. Do not spray blooming crops. Obviously that doesn’t work when bad insects are above threshold when the crop is blooming.
3. Consider culture practices that help to reduce some insect pests.
4. Use tip, pressure, and labeled spray additives that reduce vapor and fine droplet drift.
5. One article says to use lower label rates. Be careful about that. Lower rates can increase the risk for insect resistance. Also, if you have to spray a second time, that could be worse.
6. Consider wind direction related to vegetation that is inviting to bees.
7. Use the Bee Watch program to know where hive are and meet your neighbors.
8. Be wise about where you plant bee habitat. For example, I don’t think I’d plant flowering plants for bees in buffer strips close to fields that I might need to spray with insecticide sometime.
a. Weather and other factors don’t always give us the best options. Sometimes we have to make difficult choices.

Reminder: Todd County Dairy Tour, Aug. 8, 10:30 to 12:30. Donnie and Carolyn Middendorf currently milk 100 cows in a double 8 swing parlor, installed 5 years ago; and use a 3-row sand bedded freestall barn. The Middendorfs are transitioning to organic production. Call Brenda Miller at 320-732-4435 to RSVP or with questions.


Daniel Martens
Extension Educator, Ag Production Systems
(320) 968-5077
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