 |
||||||||||||||||||||||||
 |
||||||||||||||||||||||||
 |
||||||||||||||||||||||||
       |
Grasshoppers - Melanoplus spp.
 HOSTS:
Grasshoppers
are general feeders and some will feed on most any green plant under
certain conditions. LIFE
CYCLE: These
species overwinter in the egg stage in the soil. Eggs are laid in pods
in the soil during late summer and fall and nymphs begin emerging in
April, May and June. Researchers have found that grasshopper hatch
often corresponds with the time lilacs are in full to late bloom.
Nymphs feed on vegetation for 40 to 60 days before molting into the
adult stage. Adults disperse to suitable hosts during the summer and
can do serious damage to crops and rangeland. Adults mate in late
summer and lay the overwintering eggs. In most areas, eggs are laid in
waste areas along roadsides and around field margins, especially in
grassy, south-facing areas. CONTROLS:Cultural: Temperature and moisture are important factors in reducing grasshopper populations. Heavy mortality occurs in the spring if cool, wet weather follows warm weather which causes premature hatching of eggs. In late spring, short periods of hot weather increase the incidence of fungus and bacterial diseases. The best time to control grasshoppers is during early nymphal development when they are most vulnerable to disease, parasites, predators, insecticides and inopportune weather. Grasshoppers breed and grow in weedy, undisturbed areas like roadside ditches, fence rows, untilled pastures, and in crops that continue longer than a single growing season. After the eggs hatch, a survey of the area helps to ascertain where populations are developing. Optimal control is possible when the insects are still immature and restricted to their breeding areas. Adult grasshoppers are difficult to control, hence preventative management is of the essence. Late summer tillage discourages females from laying eggs in the ground. Tillage also destroys eggs by exposing them to the weather, predators and parasites. Spring tillage eliminates food sources for the newly hatched nymphs. Fall tillage may not be compatible with the goals of sustainable farming because it reduces winter cover necessary to conserve water and prevent erosion. Spring tillage may be the more (ecologically) sustainable option. Trap crops (small plantings established within or next to the main crop to draw the pests away and concentrate their populations where they can be destroyed) such as untilled strips of vegetation left after spring tilling, may serve to attract nymphs that are mobile enough to search for food. In summer, to protect crops from migrating populations, uncut strips or trap crops may be left between the crop and the direction where the grasshoppers are coming from. In the case of a market garden, an irrigated "greenbelt" along the perimeter will act as a trap crop when the surrounding vegetation begins to dry up in late summer. Grasshoppers are drawn to monocultures and dislike nitrogen-fixing crops like peas and sweet clover. Rotation, cover cropping and other practices that promote bio-diversity make farm habitat more attractive to the host of natural predators and parasites that control localized grasshopper infestations. A survey by the USDA's Grasshopper Control Project in 1938-40 showed that 15% of grasshopper egg pods in western and midwestern states were destroyed annually: 6.9% by flies, 5.6% by blister beetles, and 2.5% by ground beetles. Domesticated livestock, such as chickens, turkeys, guinea fowl, geese and ducks are good for keeping grasshopper populations in check, although they tend to damage the plants in the garden, too. Biological: A well-known biological control for grasshoppers is Nosema locustae, a naturally occurring protozoan that causes disease and death in crickets and grasshoppers. Spores of the parasite are impregnated into wheat bran flakes and applied by hand. It takes between one and five weeks for the grasshoppers to be infected. Following ingestion, the spore ruptures and activates the disease in the grasshopper. Infected individuals are lethargic and slow, making them easy prey for birds. Nosema locustae is not toxic to birds, animals or other insects. The trade name is Semaspore. When using Nosema locustae, growers should locate spring hatching areas. Bait broadcast over these locations will sicken and kill the nymphs. Nosema is effective against adults too but most effective against the second and third instar nymphs. Reports on the success of N. locustae are mixed. It is not a good "rescue" treatment and will not result in instant adult mortality. According to Jerome Onsager, one of the first Nosema researchers at the USDA Rangeland Insect Laboratory in Bozeman, Montana, Nosema was developed as a management tool, not to provide instant control. The fungus Beauveria bassiana is yet another biopesticide registered for grasshopper control. Beauvaria bassiana (BotaniGard) and spinosad (Conserve SC) reduced grasshopper populations in a CO study. Canola oil added to grasshopper sprays increases mortality because canola oil attracts grasshoppers. Also in the above CO study, neem (Bioneem and Trilogy) and hot pepper wax reduced feeding. Garlic is reportedly effective too. Garlic spray may be made at home or purchased. Directions for making your own spray are as follows: Soak three ounces of finely-minced garlic cloves in two teaspoons of mineral oil for at least 24 hours. Add one pint of water that has ¼ ounce of liquid dish soap mixed into it. Stir well and strain into a glass jar for storage. Combine one tablespoon of this concentrate with one pint of water to make a spray. |
|||||||||||||||||||||||
|
|
||||||||||||||||||||||||
 |
||||||||||||||||||||||||
