Southeast Michigan field crops update – May 27, 2021

Watch for potato leafhoppers in alfalfa.


Potato leafhoppers will be in alfalfa until fall frost. This insect blows in on the warm Gulf air currents then feeds on alfalfa and many other crops in Michigan. Potato leafhopper is a small, bright green insect with piercing, sucking mouthparts that inject saliva to block the normal flow of nutrients in the plant. Initial leaf damage is a wedge or V-shaped yellowing of leaf tips known as hopper burn that can stunt plants, reducing yield and life of the stand.

Now that the first cutting has been taken, scout fields for this pest. The treatment threshold for non-potato leafhopper resistant alfalfa is based upon the height of the new growth and a hopper count using a sweep net to capture hoppers. If an insecticide treatment is necessary, avoid spraying when bees may be out and look at the preharvest interval of the product. Treatment is more justified for a newer stand, whereas treatment of an older, thinner alfalfa stand may not be warranted unless infestation is very heavy.


Corn planted in April and early May should have emerged, and a final stand count can be taken. Stand counts in 30-inch rows should be conducted in a 1/1000th acre, or 17 feet and 5 inches length of row. Farmers with stand count concerns should first check with their seed dealer or company agronomist. As the calendar approaches June, it becomes more difficult to justify tearing up an existing stand for a complete re-plant. A new stand of 30,000 seeds planted on May 29 has an optimal yield potential of 81% as compared to the same population for a field planted on April 30, which is the 100% optimal yield.

Corn planted into weedy residue will be attractive to insects such as black cutworm and armyworm. Scout fields to look for cut plants or chewed and ragged corn leaves.

Soybeans and insects

Chris DiFonzo, Michigan State University Extension field crops entomolist, has reported seedcorn maggot in soybeans. Most soybean fields have more than enough seeds so the loss of some to maggots would not be noticed. Farmers on the very-early-planting schedule expose soybeans to more time in the maggot life cycle and to soybean seeds that were planted in cooler and wetter soils. The MSU Enviroweather website not only gives weather information but has predictive models for insects such as seedcorn maggot.

Soybean yield contest

The Michigan Soybean Association is sponsoring a 2021 soybean yield contest for Michigan farmers. The entry fee is $25 for Michigan Soybean Association members or $100 for non-members, which includes a one-year membership. There are six categories for maturity, irrigated and non-GMO.


Farmers with soft white or soft red winter wheat should be scouting wheat fields for Fusarium head blight or head scab. The Penn State Fusarium Head Blight Risk Assessment Tool is the best guide to help assess the relative risk of this disease and determine any spraying. Favorable weather includes warm, wet, humid conditions prior to and during flowering and early grain fill. Cool conditions slow fungal growth and sporulation.

Michigan Soybean On-Farm Research Projects for 2021

Cooperators are still needed in southeast Michigan. If you are interested in becoming a partner, please contact Ricardo Costa, MSU Extension field crops educator, at 573-639-8971 or [email protected] to request a detailed protocol for each of the projects. There are 13 projects to choose from, ranging from planting rates to fungicide application.

Adapted from Field Crop IPM Report published by Ned Birkey, Spartan Agricultural Consulting, LLC