Powder River Examiner -

Courtesy PR Extension Office

The prediction for a heavy grasshopper infestation this summer has certainly proven correct – memories of 1988 are being shared by those who dealt with a severe infestation at that time, according to Powder River Extension Agent Mary Rumph.

“Unfortunately, all the environmental factors that could have helped reduce the population didn’t happen,” said Rumph. “For example, cold, wet weather is very destructive to newly hatched grasshoppers. Alternatively, very dry winter and spring conditions also can be harmful to grasshopper survival since required tender new plant growth is not available. We had just enough soil moisture to provide vegetation when the hatches occurred, providing feed early on,” she added.

Some insects commonly feed on grasshoppers. Many species of blister beetles develop on grasshopper egg pods and blister beetle abundance cycles along with their grasshopper hosts. Unfortunately, the blister beetles also feed on desirable vegetation. Adult robber flies are common predators of grasshoppers during summer and other flies develop as internal parasites of grasshoppers. Many birds, notably horned larks and kestrals, feed heavily on grasshoppers. Grasshoppers are also frequently eaten by coyotes.

Grasshoppers are also subject to some unusual diseases. A fungus (Entomophthora grylli) infects grasshoppers causing them to move upwards and cling to plants shortly before they kill the insect host. Stiff, dead grasshoppers found stuck to a grass stem or twig indicate infection with this disease. A very large nematode (Mermis nigriscens) also sometimes develops in grasshoppers. Both the fungus disease and nematode parasite are favored by wet weather.

Managing Grasshoppers with Baits and Sprays

During periods when a local outbreak develops, control usually involves using sprays or baits. To be successful these need to be applied to developing stages of grasshoppers and concentrated at sites where egg laying occurs. Ability to control grasshoppers declines as grasshoppers develop and migrate.

Treatments should be directed at the young grasshoppers and nearby vegetation present in these breeding sites. Baits containing carbaryl (Sevin) can be broadcast. Bait formulations are made by mixing the insecticide with bran or some other carrier and kill grasshoppers that feed on the bait. These treatments limit application effects on other insects present in the treated area. Baits must be reapplied after rain.

Insecticide treatments do not need to completely cover the area since grasshoppers are mobile. Insecticides applied as bands covering 50 percent of the area, or even less, have proved very effective for control of grasshoppers in rangelands. Backpack sprayers and application equipment modified for use on ATVs can be used in larger acreages.

Once grasshoppers have reached the adult stage and migrations occur, some insecticides may be applied directly to plants. Such applications have only short effectiveness and damage can occur before individual grasshoppers are killed. Furthermore, the choice of insecticides is more limited since few allow direct application to garden fruit and vegetables.

Choices of insecticides for grasshoppers include: carbaryl (Sevin) most formulations allow use on a wide variety of fruits and vegetables and is available for use in sprays, dust and in baits; acephate (Orthene) has systemic activity in plants and may persist longer than most other insecticides and uses are limited to non-edible crops; permethrin (many trade names) widely available for garden use and most formulations allow use on a wide variety of fruits and vegetables, short duration. Most important is to follow the instructions on the label, stated Rumph.

Nosema locustae Baits

Baits containing the protozoan Nosema locustae is a biological control option that may be considered for treating grasshopper breeding sites. This is sold under the trade names NOLO Bait or Semaspore and can produce infection of many species of grasshoppers. Because it is selective in effects, only affecting grasshoppers, its use is sometimes considered desirable.

There are some limitations to Nosema locustae baits. Only young grasshoppers are susceptible, and it cannot be used effectively after adult migrations have occurred. It is also fairly slow acting and does not equally infect all grasshopper species. Often it is most effectively used in a long-term grasshopper management program, in combination with other controls.

Nosema locustae baits are also perishable. They are best kept refrigerated before use. Expiration dates are usually printed on packages and should be checked.

Other Controls

If insecticides are not used, some protection of a garden may be possible by watering grasshopper breeding areas to promote plant growth. This may retard migrations of grasshoppers to areas of more desirable plants. Mowing or other activities that deny food plants in breeding sites should be avoided.

Susceptible plants may be protected by screening or cheesecloth barriers. However, grasshoppers can chew through most fabrics.

Repellents do not appear to be effective. Some materials used as repellents, such as vegetable oils and garlic-based preparations, may instead increase grasshopper feeding on plants.

Poultry may feed heavily on grasshoppers. Turkeys, guinea hens, and chickens have all been used to help control grasshoppers. However, garden areas may need to be fenced since scratching by chickens can be harmful to young plants.

“Philosophically, this may be one of those summers that you choose what you want to save; whether it is your garden, lawn, flowers, trees or siding on the house,” said Rumph. “Unless something happens to slow the impending devastation that will occur as the current population continues to feed and grow; be prepared to wage battle.”

“I draw the line at the trees in my yard,” added Rumph. “I will do whatever is necessary to protect my trees from grasshoppers, siding can be replaced!” she concluded.