Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
10/5/98
Yard and Garden Column for the Week Beginning Oct. 5
Contacts:
Donald R. Lewis, Extension Entomology, (515) 294-1101
Elaine Edwards, Extension Communication Systems, (515)
294-5168
Grasshoppers Go Crazy In The Fall
By Donald Lewis
Extension entomologist
Iowa State University Extension
It happens every autumn. Someone calls to describe what they hope will be the unprecedented observation of the century that will bring them fame and notoriety, or at least a spot on the evening news. But it turns out to be the same thing we've seen before; grasshoppers behaving in a most un-grasshopper-like fashion.
It is no exaggeration to describe the behavior of some grasshoppers in the fall as crazy. It is also no exaggeration to say we don't know why. But there they are, grasshoppers eating the fresh paint right off the side of the house. Or grasshoppers eating holes through the plastic window screens. We also have seen grasshoppers eating the edges from wooden fence and deck boards or eating the cardboard signs put up in the fields or along the road. It seems nothing is safe from consumption by crazed hoppers, not even evergreen tree needles and bark.
So what are grasshoppers supposed to eat? In a word, grasshoppers eat grass. And of course they also eat other green, succulent vegetation such as flower foliage, bean leaves and assorted parts of other living plants. It is the consumption of synthetic materials such as paint and plastic that is the most befuddling.
Grasshopper life cycle
There are three stages in the grasshopper life cycle --
the egg, nymph and adult. The grasshoppers commonly found in
Iowa spend the winter as eggs in the soil. The eggs begin to
hatch in June to early July and tiny, wingless grasshopper
nymphs appear in areas of tall grass, weeds and other dense
vegetation. The nymphs feed and grow for 40 to 60 days and
gradually spread to adjacent areas (into tilled garden and
flower beds, for example). By late summer or early fall the
grasshoppers have completed their growth and are full-grown,
winged adults. By that time they also have usually spread
into widely separated areas.
The biological function of adults, that is, to reproduce and perpetuate the species, is accomplished when the females lay their eggs following mating with a male. Females deposit egg pods one to two inches deep in the soil, usually in areas of sod or other grasses. The number of egg pods deposited by a single female may range from seven to 30, depending on the species, and the number of eggs per pod may vary from eight to 30, again depending on the species.
Craziness only in the fall
Adult grasshoppers continue to feed until they die of
old age or are killed by freezing temperatures, whichever
comes first. It is in this period of waiting-to-die that we
see the aging grasshoppers eating 'unnatural' foods such as
window screens and latex paint. It is after the eggs are
laid, after the biological destiny has been fulfilled, after
Nature has no further expectations of the grasshoppers that
they seem to go crazy.
If grasshoppers had thoughts, feelings or human qualities we could imagine this weird behavior is the outcome of senility. Or maybe it is boredom. It might even be revenge for decades of insecticide use. But unfortunately, such anthropomorphism does not really explain why the grasshoppers are behaving badly, it only describes how we would feel if we were grasshoppers.
Even without an adequate explanation for the behavior we can formulate some management strategies. First, insecticides will provide very little relief from grasshopper aberrant feeding behavior. In other words, spraying will probably not save your screens or keep grasshoppers from eating your siding paint.
If you do intend to control grasshoppers you should start early and treat a large area. Apply insecticides to the places of grasshopper origin (grassy areas) while the nymphs are still small. Available insecticides are notoriously ineffective in killing the full-grown adults. Grasshoppers are very mobile and move large distances during their lifetime. Spraying a large zone and not just the affected area usually provides better control.
A solution more practical than insecticides is to wait until after frost to finish your late summer painting project. Also, wait until the population declines to replace your plastic window screens with metal screens, at least around the ground level. And finally, show some pity. You too will be old someday and may engage in behaviors that others find hard to explain.
ml: isugarden
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