CO-Horts Blog

Tuesday, March 3, 2020

Control of Grasshoppers

1402129 Grasshopper damage - by R J Reynolds Tobacco Company
If you are seeing holes and gnarly places chewed in your plants, it could be the result of hungry grasshoppers. Sometimes we do not really think much about grasshoppers until they become large and begin showing up everywhere. By then, it might be too late to control them.

If you live in the country, you may experience more grasshoppers than your friends in town. This is because grasshoppers prefer to lay their eggs in the fall, in dry undisturbed areas such as fields, pastures, roadsides, or empty lots. Depending on the weather, the eggs will begin to hatch in mid to late spring. 

After the nymphs are born, they begin feeding on lush green vegetation in the immediate area. As plants begin to dry up with the summer’s heat, and moisture becomes less available, food sources grow scarce and the hoppers begin moving to more desirable locations, namely your lush yard. 
Two striped Grasshopper, Linda Corwine
A female grasshopper can lay up to 400 eggs, found about ½ inch under the soil. Many of the nymphs will die before they become adults, but with that many eggs being laid it doesn’t take long for their populations to become extensive. Fortunately, there are many natural predators such as birds, nematodes, blister beetles, robber flies, skunks, and occasionally coyotes and wolf spiders to help control their populations.

While a few grasshoppers in the garden are expected, and cause no real damage, populations can become quite large taking its toll on your plants. Within 16 hours, a grasshopper can eat its own weight in green food. This is not bad if you only have a small population to deal with. It is said that if you have 7 grasshoppers per square yard over a 10-acre field, they will eat the same amount as a cow! I am not sure how much a cow eats, but I have seen plants severely damaged in a very short period.

The good news is, there’s a great organic pesticide that can help solve the problem. Nosema locustae, a fungi called Microsporidia, is mixed with wheat bran, which is a favorite treat of grasshoppers. As the unsuspecting grasshopper eats the bait, the fungus infects the hopper’s stomach, producing a chronic disease. Because this takes a while to act, patience is required. In fact, the populations may not decrease until the following season. The bait can also control earwigs (which can be considered either a beneficial or troublesome insect), cutworms, crickets, and sowbugs. It’s not harmful to mammals or beneficial insects such as bees!
Nolo Bait, Linda Corwine Photo

The Microsporidia is sold under various trade names such as Nolo Bait or Semaspore. It i commercialized by mass production in laboratories. You may have had a hard time finding Nolo Bait in previous years because there was a fire at the factory in Durango in 2018. The supplier of Semaspore put the business up for sale. However, it should be in good supply again this season. Because this is a living organism, it only has a one-year shelf life and must be stored carefully.  Homemade baits can be made, but are not safe around children and pets.

Baits will work much more effectively on young grasshoppers when applied in the evening hours, and when it’s cooler. Some grasshoppers actually prefer to feed at night, rather than during the day. Most grasshoppers will stop feeding when temperatures become too hot.

Treating the areas where the grasshoppers are hatching will give the best results, but this isn’t always possible. A barrier strip of grass, weeds, or flowers, around your property can be a good place to treat grasshoppers if chemicals are required. Just make sure that your barrier does not consist of weeds that are invasive varieties. Carbaryl, permethrin, and acephate are all effective products.

Grasshopper control is not a one-time shot with a pesticide. In spite of your best attempts, some hoppers inevitably manage to find their way to their favorite foods. Crops such as lettuce, rhubarb, tomatoes, and corn are always on the menu. Because they feed on such a large variety of plants, take time to inspect your garden and observe who’s having a hopping good time.

For additional information refer to Fact sheets 5.535 and 5.536

Linda Corwine McIntosh
Colorado Master Gardener Tri River Area, ISA Certified Arborist, Commercial Pesticide Applicator

1 comment:

  1. Question: Can it hurt birds in any way that eat these sick grasshoppers?
    I have tried to rethink harmful insects in my garden as free, high protein bird food. Last year I had an invasion of blister beetles which ate my clematis plants. After reading about them, I found they had one redeeming quality, their larvae eat grasshopper eggs. Although my clematis grew back it didn't bloom, so I'm planning on using diatomcious earth around the area near these plants. My garden around my house is organic and although my plants don't always look perfect, I know I'm not going to be on a garden tour and I love all the birds that visit. Thank you for your interesting article. I plan to copy it in notes in case I get a grasshopper invasion.