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Early Season Grasshopper Emergence (05/20/21)

With crop emergence now underway throughout North Dakota, crop scouting for young grasshoppers is just around the corner.

With crop emergence now underway throughout North Dakota, crop scouting for young grasshoppers is just around the corner. Grasshopper eggs will begin to hatch from grassy overwintering sites in the 2021 05 19 17 29 28coming weeks. Newly hatched nymphs are small about the size of a wheat kernel and pass through 5 to 6 molts, depending on species, before reaching adulthood. The grasshopper nymph can be differentiated from the adult based from the lack of wings that are present. Nymphs have wing pads (undeveloped wings) and are unable to fly. As a result, they must crawl into crop emerged areas from grassy hatching sites.

Grasshopper development is often favored by warm, dry weather whereas cool, wet weather can increase disease incidence and slow the development of grasshoppers, thus reducing the overall population. As we observe the forecast for the last two weeks of May, we see a slightly cooler than normal forecast with an equal chance of wet or dry conditions. However, the overall summer forecast appears to trend towards a drier and warmer period through the month of August. Overall, the long-term forecast appears favorable for grasshopper development.

Grasshoppers, in high numbers, can lead to significant crop defoliation under hot, droughty conditions. Using their chewing mouthparts, young grasshoppers can cause severe defoliation.  Adult grasshoppers often chew on reproductive parts (corn ear, wheat or sunflower heads), and can clip heads or pods of crops near the end of the growing season.

Crop scouting is important as populations can fluctuate due to weather conditions. Scouts can use four 180-degree sweeps with a 15-inch diameter sweep net (equivalent to one square yard) to find the number of nymphs in the grassy ditches near emerging field crops. Early detection of nymphs is important for proper pest management.

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TJ Prochaska

Extension Specialist/Crop Protection

NDSU North Central Research Extension Center

 

Janet Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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