How To Prevent A Plague Of Grasshoppers

Good bug, bad bug.

April 21, 2011
Grasshoppers made it onto the top-10 list of biblical plagues for good reason. During serious outbreaks, says entomologist Whitney Cranshaw, author of Garden Insects of North America, "they'll eat anything. Beans. Roses. Berries. Anything." 
Unpredictable, grasshoppers can appear 2 or 3 years in a row or disappear for a decade. In large numbers, they can defoliate entire fields. Much more rarely, they'll form into clouds and migrate in search of food. "That's when people call them locusts," Cranshaw explains. "Think of them as grasshoppers gone berserk." 
There are hundreds of grasshopper species. Many, but not all, are garden pests. Most grasshoppers lay eggs in the soil in early autumn; they prefer areas of dry, untilled ground. Nymphs, which look like adults but are smaller, emerge the following spring to feed on young, green growth. They gain size and strength through each progressive molting—the shedding of an exoskeleton. Forty to sixty days after hatching, grasshoppers become adults with functioning wings. 
Minor to moderate grasshopper invasions can be handled with organic methods. The key to control is to start early, during the insects' nymph stage, because adults are harder to kill. Some strategies: 
  • Encourage predators. Larks, bluebirds, and kestrels eat grasshoppers. So do chickens and guinea hens, which can eat as many as 2 pounds of the insects per day. 
  • A healthy, biologically active soil encourages blister beetles and the numerous microscopic predators known to cause diseases in grasshoppers. 
  • Nosema locustae—living spores of a microbial pathogen sold as NOLO Bait or Semaspore—infect and kill some grasshopper species, if applied early. 
  • Fabric and aluminum-screen row covers will protect young plants, though grasshoppers have been known to chew through both. 
  • Lush, green weeds and tall grasses attract 'hoppers, so keep weeds under control. But mowing vegetation after grasshoppers appear may prompt the insects to migrate to your crops. 
  • Finally, till in autumn to expose overwintering eggs, and again in spring to kill young weed seedlings.