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Hopper havoc

Grasshoppers invade Montana's farms and ranches

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As you walk through the fields at Pommes de Terre Farm in Dixon, you’re certain to notice the grasshoppers. In fact, you literally can’t miss them. They leap and take flight, billowing up before you in clouds, smacking into your body and face, squishing under your shoes like an Egyptian plague of biblical proportions. The lettuce, kale, and many of the potato and cabbage plants have been stripped down to their skeletal stalks. The farm’s co-owner, Jane Kile, a longtime western Montana grower, has never seen the grasshoppers like this. By nature unflappable, she is nevertheless concerned.

While these may not be biblical times, by all accounts 2002 is shaping up to be a bad grasshopper year (for us humans, at any rate) across the Big Sky. Unusually large numbers of hoppers have hatched in recent weeks, and they are hungrily working their way across Montana’s crops and rangelands. Their presence is causing difficulties and losses on farms and ranches throughout the state.

According to Laura Hinck, an entomologist with the Montana Department of Agriculture, this year’s cool, wet spring and early summer, followed by a burst of extremely hot, dry weather in July has led to local and regional population explosions.

“We’ve received calls [about grasshoppers] from all over the state,” says Hinck. In many areas, grasshopper population densities range from tens to hundreds of insects per square yard. I quickly lost count in Dixon, but the conditions on Kile’s farm are clearly at the upper end of that spectrum.

Grasshoppers are big eaters, consuming about half their body weight in green forage each day. They primarily eat grasses, but will eat broadleaf plants and crops as well, particularly when surrounding pastures are insufficient to sustain them. Hordes of grasshoppers are also capable of migrating significant distances in search of food.

Many farms and ranches are taking measures to control grasshoppers. The most common control strategy is the application of chemical pesticides. Carbaryl (its trade name is Sevin) is a pesticide that is recommended, sold and applied widely to control grasshoppers and other insects, both here in Montana and throughout the United States. Carbaryl (naphthyl methylcarbamate) is a toxic chemical that is teratogenic—or known to cause cancerous tumors, particularly in the testes and reproductive organs of animals. However, studies on the correlation between carbaryl exposure and human cancer rates have never been done. Other chemical pesticides used to control grasshoppers include malathion and diflubenzuron (whose trade name is Dimilin). According to Hinck, pesticide spraying is most commonplace on cropland, which potentially has a higher rate of return than pastures and rangeland.

Pesticide use can be significantly reduced by using integrated pest management techniques such as RAAT (reduced agent and area treatment). These can reduce the amount of chemical pesticide used by more than 50 percent while maintaining comparable overall efficacy, according to research done at the University of Wyoming. With this strategy, the pesticide is applied in swaths, allowing grasshoppers’ predators and parasites to be preserved in the untreated swaths. The University of Wyoming researchers have concluded that this approach significantly reduces the cost of pest control as well.

For organic farmers, options for dealing with grasshoppers are, as one might expect, a bit more creative. In small acreage situations, physical barriers such as cheesecloth can be draped over vulnerable crops to protect them. Another organic control method is the use of a natural spore called nosema locustae, which is harmful only to grasshoppers. These spores, released around gardens and crops, can be an effective biological control on a short- and long-term basis. Kile’s farm is utilizing both of these strategies. Also, chickens (as well as many other birds) are voracious eaters of grasshoppers. Chris Dement and Bri Warner, organic farmers who grow vegetables on a Moiese Valley farm that is also home to several hundred free-range laying hens, aren’t finding grasshoppers to be any problem whatsoever. “We don’t have a whole lot of grasshoppers around here,” says Dement with a laugh. “But the chickens, now they can be a problem!”

Thus far in Montana, crop and revenue losses have been minimal to moderate. However, the damage is ongoing and the ultimate extent of crop and revenue loss remains to be seen. Several factors will affect the amount of loss, including the remainder of the season’s weather and commodity prices.

So what is the long-term prognosis on the impacts of grasshoppers and other insects on Montana’s farms and ranches? It is important to keep in mind that insect infestations are cyclical events, and that they happen periodically even in the healthiest ecosystems. Naturally, damage and loss at some level is to be expected, particularly in organic settings.

However, it is also clear that climate destabilization, which is a more accurate way to describe the phenomenon known as global warming, is already causing increased incidence of erratic weather events and unusual or extreme weather conditions such as storms, heat and drought. These conditions may well contribute to insect plagues and other anomalous natural events occurring with greater frequency. Time, it appears, will answer that question.

For more on grasshoppers and integrated pest management: www.sdvc.uwyo.edu/grasshopper/ For more on nosema locustae spores and other organic and low-impact control methods: www.planetnatural.com/grasshopperpamphlet.html

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