Grasshopper Control in Grdens
I often get calls related to grasshoppers. According to Texas A&M AgriLife Extension information, grasshoppers have many natural enemies that help control their populations. A fungus, Entomophthora grylli, often kills many grasshoppers when the weather is warm and humid. Infected grasshoppers strike a characteristic pose at the top of a plant or other object. The grasshopper grasps the plant in a death embrace with the front and middle legs, while the hind legs are extended. It dies in this position. Fungal spores develop in and on the grasshopper’s body, then become airborne and infect other grasshoppers. Another natural enemy is a protozoan, Nosema locustae. Its spores have been incorporated with bran to make insecticide baits such as Semaspore®, Nolo Bait® or Grasshopper Attack®. These baits kill some nymphs but almost no adults, though infected adults lay fewer eggs. Baits act too slowly and kill too few grasshoppers to be useful for immediate control. Other natural enemies include nematodes called hairworms and insects that feed on grasshoppers, such as the larvae of blister beetles, bee flies, robber flies, ground beetles, flesh flies and tangle-veined flies. Birds (quail, turkey, larks, etc.) and mammals also eat grasshoppers, but have little effect on large populations. Most of the time, we suffer big strikes of grasshoppers due to long periods of drought and high numbers of grasshoppers. Because residents of urban communities generally have little control over the surrounding countryside, management options for grasshoppers in urban landscapes are limited, according to Michael Merchant, Urban entomologist for AgriLife Extension in Dallas. According to Merchant, homeowners can protect valuable plants, to some extent, through the use of residual insecticides. Geotextile fabrics can be used as barriers to protect valuable vegetables and specimen ornamental plants. Also, landscape plants that are less attractive to grasshoppers can be used.Recent tests have shown that insecticides containing bifenthrin (found in some Ortho® Home Defense? products) and lambda-cyhalothrin (Scimitar®) provide the fastest knockdown and longest residual control. Products containing permethrin (several manufacturers), cyfluthrin (Bayer® Advanced Lawn and Garden products), and esfenvalerate (Ortho® Bug-B-Gone) should also provide good control. Insecticides containing chlorpyrifos, diazinon and carbaryl will provide control of shorter duration. Geotextile fabrics have found increased use among vegetable gardeners as floating row covers to protect plants. These fabrics are light enough to permit needed sunlight and air circulation to occur within plants that are covered, yet strong enough to provide a barrier to many insects. During heavy grasshopper infestations, even these barriers may be damaged by hungry grasshoppers. It may be necessary to apply insecticides (that are labeled for the plants being protected) to the fabrics before they are used to cover the plants. Some plants that require insect pollination may require hand pollination when covered by row covers. These fabrics may be obtained through some garden centers and via mail-order garden supply catalogs.
Mario Villarino DVM, Ph.D.
Hopkins County Extension Agent for Ag and NR
1200B Houston Street
Sulphur Springs, Texas 75482