JoAnne Skelly
My friend Cat asked me to identify what was eating the bottoms, and only the bottoms, of her cherry tomatoes. While it could be birds, earwigs, slugs or cutworms, we both decided it was grasshoppers, which she had seen eating her raspberries. If raspberries, why not tomatoes?
I’ve seen a few grasshoppers jumping around, but not enough to be concerned about. Although there are 118 species of grasshopper in Nevada, less than 10 species are problems. Surprisingly, all grasshoppers are not pests. Some are beneficial depending on their food habits. Those that are detrimental to agriculture and horticulture can eat up to one-half their weight in plant material in one day wreaking havoc on a landscape.
A female grasshopper lays an average of 200 eggs in her yearlong lifetime. In a good food year with warm dry conditions, she may lay up to 400 eggs. The eggs begin hatching in April and May, peaking in mid-June. Cool and extremely dry springs may delay the hatch until July.
Nymphs develop for 8 to 10 weeks, becoming adults 9 to 11 weeks after hatching. Grasshoppers are prey not only to birds, mammals and other insects, but also to parasites that attack their eggs and nymphs. They are careful in their food selection, which may be why Cat saw damage on only part of the cherry tomatoes.
Grasshoppers are most active after basking in the morning sun for a couple of hours, then again in late afternoon. Since they are less active in the early morning, that is a good time to catch and destroy them. A sweep net or quick hands can remove them from vegetables and plants throughout the landscape.
Put them in a container and dispose of them or crush them. Digging and cultivating in the spring exposes the eggs to predation. Keeping areas weed free discourages egg laying. Two-feet tall barriers can keep nymphs out of vegetable gardens because they do not jump high. Barriers must have a smooth surface and bend away from the area to protect against these great climbers.
Heavyweight floating row covers are another deterrent. If the material is too thin, grasshoppers chew through it. Shallow pans or buckets filled with a 10 percent solution of molasses and water can be used to trap them. Cover the solution with a film of canola oil to deter bees and mosquitoes. Remove the grasshoppers daily.
Cat has found that sprinkling flour on the leaves and around the base of the plant kills them off. She suspects the flour gums up their mouths. Some people have zero tolerance for grasshoppers, particularly if an undamaged landscape is their goal. Others don’t mind them unless they see significant damage to their plants.
FYI – The Nevada State Tree Nursery in Washoe Valley will be open Sept. 7 through Oct. 14, Thursdays and Fridays, 9:30 a.m. to 3 p.m. and Saturdays by appointment only. https://forestry.nv.gov/washoe-state-tree-nursery.
JoAnne Skelly is Associate Professor & Extension Educator Emerita at University of Nevada Cooperative Extension. Email skellyj@unr.edu