Dakota Farmer

Manage grasshoppers early for best results

Don’t wait until damaging populations of grasshoppers make your crops home.

Sarah McNaughton, Editor, Dakota Farmer

June 20, 2024

3 Min Read
grasshopper on grass
SPOT THE HOPPERS: The USDA says that the threshold for grasshopper population is 15 to 20 nymphs or eight to 10 adults per square yard. If thresholds are exceeded, growers should apply an insecticide that is labeled for grasshopper management. Karl Ander Adami/Getty Images

Monitoring grasshopper populations is vital to preserve crop quality and yield in the summer months. Grasshopper hatch typically spans between early May to the end of June, and they’re easier to treat during the nymphal stage.

Growers can manage grasshoppers and the damage they bring to crops through careful scouting on at least a weekly basis and employing proper insecticides when they reach the economic threshold.

Scouting and sweeping

While scouting each week for small grain crops is enough, North Dakota State University says that broadleaf crops such as sugarbeets, sunflower, canola, dry beans and soybeans are more susceptible and should be scouted twice a week.

Knowing the approximate instar or growth stage of the insect is helpful, as it can determine how far the hatch has progressed. It takes about 40 to 60 days for a grasshopper to mature from egg to adult, and there are generally five to six nymphal stages. Once growers find fourth and fifth instar insects, the year’s hatch is coming to an end.

Newly hatch grasshoppers usually don’t require treatment unless the economic threshold reaches “threatening” level. This age insect is about the size of a wheat kernel, and population can be difficult to count. However, grasshoppers are easier to control in nymphal stages.

Using a sweep net as the scouting tool of choice, make four 180-degree sweeps with a 15-inch net. Then, count to determine the number of grasshoppers per yard.

How can you determine when the population has reached the point of economic damage? NDSU shares this graph:

Rating of Grasshopper infestations by count of nymphs and adults  table

Treating the smart way

The benefit of frequent and early scouting is that grasshoppers are easier (and cheaper) to control when they are younger. NDSU says that fewer acres have to be treated and use less insecticide. They are killed before they have the chance to cause too much damage to crops, smaller insects are more susceptible to insecticides, and treating early prevents grasshoppers from reaching maturity and depositing eggs.

When deciding which insecticide to use in grasshopper treatment, take careful consideration into location, crop growth and insect instar stage. In less mature crops, insecticide applications only will protect the present leaves, leaving new growth unprotected. Better results can be seen as canopy closure continues.

NDSU says to avoid insecticide applications unless absolutely necessary. Repeated application can kill beneficial insects and lead to flare-ups of other pests. Always read the label no matter what chemical you use, including maximum seasonal-use limits. If more control is needed, it’s best to rotate modes of action to minimize the chance of insecticide resistance.

Organophosphates, pyrethroids and diamides are all options, although NDSU says that there are considerations to each type of chemistry. Chlorantraniliprole has been found to be effective in controlling grasshopper nymphs and is labeled for use in most crops. Be sure to follow the label as directed when mixing to minimize the risk of crop injury.

All in all, as the threat of grasshoppers still is unknown this season, be prepared with a treatment plan to protect crops from damage.

The NDSU Extension contributed to this article.

About the Author(s)

Sarah McNaughton

Editor, Dakota Farmer, Farm Progress

Sarah McNaughton of Bismarck, N.D., has been editor of Dakota Farmer since 2021. Before working at Farm Progress, she was an NDSU 4-H Extension agent in Cass County, N.D. Prior to that, she was a farm and ranch reporter at KFGO Radio in Fargo.

McNaughton is a graduate of North Dakota State University, with a bachelor’s degree in ag communications and a master’s in Extension education and youth development.

She is involved in agriculture in both her professional and personal life, as a member of North Dakota Agri-Women, Agriculture Communicators Network Sigma Alpha Professional Agriculture Sorority Alumni and Professional Women in Agri-business. As a life-long 4-H’er, she is a regular volunteer for North Dakota 4-H programs and events.

In her free time, she is an avid backpacker and hiker, and can be found most summer weekends at rodeos around the Midwest.

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