Integrated Crop Management

Diseases are killing grasshoppers

Grasshoppers in Iowa are now dying from infection by several insect pathogens. These pathogens are causing disease that may devastate grasshopper populations in corn and soybean fields before the first frost.

Entomophaga fungus is a widespread and common pathogen of grasshoppers in North America. The advanced stage of the disease is easy to recognize. Shortly before the grasshopper dies, it climbs to the top of a fencepost, cornstalk, or other plant where it hangs on in a death grip. It typically dies with its head pointed upward and the carcass often remains in this position for several weeks until it deteriorates.



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[1]
Differential grasshopper killed by a fungal pathogen.

Bacteria also kill grasshoppers but bacterial diseases are less well documented in Iowa. Recent, dead grasshoppers may have ruptured abdomens and ooze body fluids. These grasshoppers are less likely to be seen than the fungal-infected grasshoppers because they do not climb upward and clutch plants before they die.



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[2]
Differential grasshopper killed, probably by a bacterial pathogen.

As you walk field edges during the next couple of weeks, take a look for dead grass-hoppers on fencing wire and weeds. These dead grasshoppers are a common, but not often noticed, symptom of natural mortality.

This article originally appeared on page 178 of the IC-488(21) -- September 23, 2002 issue.


Source URL:
http://www.ipm.iastate.edu/ipm/icm//ipm/icm/2002/9-23-2002/ghopkill.html