Master Gardener: Grasshoppers – the curse of hot, dry weather

The Master Gardeners just finished another successful weekend at the Almelund Threshing Show.  Earlier I predicted that many of our questions would be on tomato problems, getting rid of Creeping Charlie, and there were two new concerns that kept coming up. Bloom drop of tomatoes, peppers, squash, zucchini, and cucumbers were one of most frequently asked about topics as well as rust fungus on hollyhocks.

We didn’t have an unusual number of questions about insects but with the heat and the off and on again hot weather, grasshoppers have become a real problem.  Not only are they taking large chunks out of the leaves of my raspberries, but they are also nibbling on the fruits as well.

Grasshoppers are in the Orthoptera family, which includes crickets and katydids.  Most features of the immature and adult insects are similar.  Only the adults have fully developed wings, however.  Coloration and patterning among nymphs also commonly change with age.  Wing pods are present on immature stages and become more prominent as maturity approaches.

Grasshoppers are some of the most familiar of all insects and more than 550 species occur in North America.  In our region we are home to four of the major species of grasshoppers. They are the Two-striped grasshopper, and the Differential, Migratory, and Red legged grasshoppers.

The general life history of grasshoppers has them spending the winter as eggs, in an elongated egg pod containing 20 to 120 eggs. Egg pods are typically inserted around the crown area or roots of plants. The eggs hatch in mid to late spring, depending on temperatures, location of the eggs and species characteristics.  In all four species, the period of egg hatch can extend over a considerable period if eggs are laid in scattered sites, or hatch may occur over a short period.

The nymphs take 5-7 weeks to develop.

Grasshoppers can show migratory behaviors. Nymphs sometimes march considerable distances in bands during outbreaks.  Adults are capable of flight and may fly several miles, often at elevations of several hundred feet.

Grasshoppers can be among the most difficult insects to control because of their great mobility.  Birds and other insects provide some natural control of grasshopper numbers but disease and weather conditions that inhibit egg hatch can also reduce their numbers.

In many areas where grasshoppers affect gardens, the source is outside the garden in areas of undisturbed soil such as fields, roadside ditches, and empty lots commonly serve as grasshoppers breeding sites.

Grasshoppers are most easily controlled with insecticides when they are still immature and their location is restricted to breeding areas.  Options for grasshopper control in these breeding areas include insecticides formulated as either sprays or baits.  These include acephate(orthene), cararyl (Sevin) and permethrin.  These can be broadcast but may also be effective if applied in bands covering 50 percent of the area. Orthene, used according to directions, can be applied to pastures, roadsides, and various trees and shrubs.  Orthene cannot be applied legally to garden crop foods.

Grasshopper baits generally contain bran or a similar carrier mixed with the insecticide carbaryl (Sevin).  Baits are easy to apply, usually effective and have little effect on beneficial insects.  Disadvantages include slightly higher costs and less availability.

— Jerry Vitalis is a Chisago County Master Gardener

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