Alberta Grasshopper Forecast

EDMONTON - Jun 29/05 - SNS -- There are several potential hotspots for grasshopper outbreaks in Alberta this year, judging from surveys done last fall, say Alberta Agriculture, Food and Rural Development, and Applied Research Association technical staff.

"In 2004, adult grasshoppers laid eggs that have the potential to become a problem this year," says Scott Meers, integrated crop management specialist with Alberta Agriculture, Food and Rural Development, Brooks. "The forecast map should help producers identify areas where infestations are likely to develop. However, conditions can change drastically from the forecast to the actual insect pressure."

Rapid change in pest populations and infestation conditions are largely driven by wet, cool weather. In 2004, the province experienced a dramatic reduction in grasshopper numbers due to near-perfect timing of rainfall events, which also resulted in a reduced need for control actions.

This year, recent rains have also taken the edge off of the predicted grasshopper population. There have, however, been reports of localized hotspots with severe to very-severe numbers of grasshopper nymphs. These areas may require control operations. It is important for producers to maintain vigilance and continue to monitor their fields. Even early spot spraying of infested areas can help to reduce the potential for large-scale outbreaks.

"Ultimately, control measures should be based on an evaluation of economic threshold," says Meers. "If populations are approaching the economic threshold and there is evidence of damage, control measures will be needed. However, if populations are below levels, and control is not warranted, the naturally occurring enemies of the grasshoppers should be allowed to moderate the population."

These naturally occurring enemies often work in tandem with weather conditions. For instance, the fungus Entomophthora grylli can effectively control grasshoppers under warm, humid conditions and may occasionally reach epidemic proportions. Grasshopper corpses left clinging to the stems of plants is a distinct indication of the disease. Other naturally occurring enemies, such as egg predators which include bee flies, blister beetles, ground beetles and crickets, may destroy up to 80 per cent of the eggs in some localized areas. Tachinid flies parasitize nymph and adult grasshoppers. This group of insects may parasitize up to 60 per cent of the nymphs and adults.

"At this point, there is no grasshopper control program anticipated for 2005; however, Alberta Agriculture, in cooperation with field staff, will continue to track the situation through pest, crop and weather reports," says Meers.