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The Garden Plot for August 17, 2007
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: “Grasshoppers”
Grasshoppers are encroaching on Western Montana gardens and landscapes. When it’s this dry, grasshoppers feed on most any green plant available. Unfortunately, the greenest plants are in our gardens right now.
Grasshoppers spend the winter as eggs in the soil. Eggs are laid in waste areas such as roadside ditches, fence rows, untilled pastures, and in perennial plantings, especially in grassy, south-facing areas. Eggs begin hatching in April and May, about the time lilacs are in full to late bloom.
The best time to control grasshoppers is soon after they hatch in the spring, when they are most vulnerable to disease, parasites, predators, insecticides and cold or wet weather. Adult grasshoppers are difficult to control; preventative management is the key to success.
Tillage destroys eggs by exposing them to dry, cold weather, predators and parasites. Tillage also eliminates food sources for the newly hatched grasshoppers.
Trap crops, such as untilled strips of perennial grass, may attract newly hatched grasshoppers. Then control measures can be applied to the trap crop. An irrigated "greenbelt" along the perimeter of gardens can act as a trap crop when the surrounding vegetation begins to dry up in late summer. Grasshoppers are drawn to single-crop plantings. They dislike nitrogen-fixing crops like peas and clovers.
Domesticated livestock, such as chickens, turkeys, guinea fowl, geese and ducks are good for keeping grasshopper populations in check, although they may also damage the garden plants.
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, first locate spring grasshopper hatching areas. Broadcast the bait over these locations. Nosema is somewhat effective against adult grasshoppers too, but most effective against newly hatched grasshoppers. Reports on the success of Nosema locustae are mixed. It is not a good "rescue" treatment. Don’t expect instant adult mortality. It may take 4-8 weeks for grasshopper populations to decrease.
If grasshoppers are eating you up now, you can try a faster acting bait. Bran baited with carbaryl insecticide kills grasshoppers as soon as they ingest it. However, this bait can be toxic to birds, insects and animals if they eat it.
Other options for grasshopper control include the fungus Beauveria bassiana and spinosad. Both reduced grasshopper populations in a Colorado study. Canola oil added to grasshopper sprays increases mortality because canola oil attracts grasshoppers. Neem, garlic, and hot pepper wax may reduce grasshopper feeding.
Helen Atthowe's new short program of gardening tips
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