Jerry Brust, IPM Vegetable Specialist, University of Maryland, jbrust@umd.edu
This season keeps with the weird and unusual with reports of grasshoppers causing damage in many different vegetables. I thought this was just an unfortunate farm 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 them. 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 rights-of-way in July with some movement into vegetables in August, but this has been a good year for grasshoppers and we have some major movement into vegetable fields now.
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 evening and even at night to avoid bee kills. 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