Grasshoppers in Vegetables

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

This season keeps with the weird and unusual with reports of grasshoppers causing damage in many vegetables. I thought this was just an unfortunate farm in southern Maryland that was having problems with them, but I have gotten calls from growers in central and northern Maryland as well as the Eastern shore about grasshoppers. There are many grasshopper species, some of the more common ones are: the American grasshopper Schistocerca Americana, Differential grasshopper Melanoplus differentialis and the Carolina grasshopper Dissosteira carolina. Normally I would expect some movement out of grain fields into meadows and along right-of-ways in July with more movement into vegetables in August. The August movement is due to everything often drying up and the only green lush growth available is vegetables and to a lesser extent soybeans. But as this has been a good year for mites, leafhoppers (which are still a problem in places) and hornworms it is also a good year for grasshoppers. Normally we just let the grasshoppers go as they usually move in and out of fields rather quickly. However on some farms they have taken up residence in some odd vegetables such as cantaloupe (Fig. 1) and peppers and need to be treated. Pyrethroids are probably the best control, but these should be sprayed in late evenings and even at night to avoid bee kills as most of our vegetables are in flower now. Organically there is not much that actually does any good; some of the baits that can be used work best on smaller (younger) grasshoppers, but poorly on adults.

Figure 1. Grasshoppers in cantaloupe