Ag practices, weird weather could explain hopper populations
Entomologist Helmuth Rogg warned Baker County growers of a potential major grasshopper outbreak in the making for 2009 during meetings in Baker City and Haines.
Baker County Extension Agent Cory Parsons points to the epicenter of the 2008 grasshopper infestation: Baker County. Entomologist Helmut Rogg warned things could get worse for Baker County growers next year without an aggressive grasshopper control program next spring. (Baker City Herald/Ed Merriman)
Rogg said the grasshopper infestation that exploded across Baker, Union and Wallow counties in 2007 zeroed in on Baker County in 2008, reaching densities as high as 200 grasshoppers per square yard in several locations around Haines, Sparta and Medical Springs.
Cory Parsons, Oregon State University Extension agent for Baker County, pointed to maps on the wall showing how the 2008 grasshopper infestation exploded in Baker County, but tapered off in Union and Wallowa counties, compared to 2007.
In 2007, the grasshopper infestation covered about 6,000 in all three counties, with densities as high as 50 grasshoppers per square yard. By comparison, Parsons said around 7,000 acres in Baker County along were infested with grasshoppers in 2008.
At the meetings held Wednesday in Baker City and Thursday in Haines attended by more than 20 growers and land managers, Rogg explained that grasshoppers do the most damage to crops and rangeland in the spring, when they are in the nymph stage during the first several weeks after they hatch.
In the last major grasshopper outbreak in 1986, Rogg said the most common species were the Melanoplus sanguinipes (migratory grasshopper) and the M. femurrubrum (red legged grasshopper)
One of the mysteries Rogg said he and others are trying to figure out is why there was a population explosion in 2007 and 2008 of the Camnula pellucia (clearwinged grasshopper), which has always been present in Baker, Union and Wallowa counties, but not in large numbers.
“The one thing we are trying to figure out is why all of a sudden a change in species occurred,” Rogg said. “Something has changed in the environment that favored Camnula over the last few years.
“In 2005 and 2006, there were no grasshoppers recorded in economic numbers in Baker County,” said Rogg, the head
entomologist with the Oregon Department Agriculture on the grasshopper infestation in Northeastern Oregon. According to USDA statistics, economic damage occurs with populations of eight to 12 grasshoppers per square yard.
Rogg said the rise of Camnula grasshoppers is troubling because in large numbers they are a significant pest in small grains and grasses when they are in the nymph stage, but they can also do extensive damage when swarms of adult grasshoppers may swarm and move into irrigated hay and pasture, potatoes and other vegetables, including onions, lettuce and peas.
“The most destructive period is in the spring when Camnula can destroy entire spring wheat fields,” Rogg said.
“Camnula populations can be low for periods of up to 10 years, then increase gradually over three to four years and reach peaks the following two or three years. During the period of increase, a population may spread from a few acres of rangeland to more than 2,000 square miles,” Rogg said in a handout titled “Grasshopper Alert for Eastern Oregon: Major outbreak possible in 2009,” which was presented to growers attending the meetings.
Rogg said things that may have led to the population explosion of Camnula grasshoppers include changes in agricultural practices, taking land out of production, less irrigation, overgrazing, fallow and weather changes, such as favorable combinations of El nino and La nina weather patterns.
Several growers in the audience at both meetings raised questions about how funds from a $50,000 cost-share grasshopper control program approved two weeks ago by the Oregon Legislature will be used to help contain the infestation in 2009.
Rogg explained that because Camnula grasshoppers do the most damage in the spring when they are nymphs, state cost-share funds will be prioritized on controlling nymphs in the spring.
“Our plan will be that we conduct our spring nymphal survey to find the hot spots. We will prepare infestation maps and assist landowners in management decisions,” Rogg said.
Management options for controlling grasshopper nymphs in the spring of 2009 will be focused on integrated pest management options, such as grazing management to increase plant cover so there’s less bare ground for grasshoppers to lay eggs, well-timed flood irrigation that can drown the hatching grasshoppers, and chemicals, Rogg said.