image: This adult orange wheat blossom midge was photographed in 2005. view more
Credit: (Photo by Phillip Glogoza.)
It is likely that Montana's typically dry weather prevents most producers from encountering a tiny pest known as the orange wheat blossom midge. However, heavy rainfall at the right time last summer appears to have helped large numbers of this insect devastate some spring wheat fields in the Kalispell area.
Before the 2006 harvest, the midge was mainly known as a minor problem in northeastern Montana counties, said David Weaver, a MSU entomologist from Bozeman.
The first verified orange wheat blossom midge in the Kalispell area came in Dan Brosten's spring wheat, where he harvested just 15 percent of a normal yield.
"We had 1200 acres of spring wheat and averaged 10 bushels per acre," said Brosten. "Normally we'd have 65-70 bushels." Brosten said he was in a field when he picked up a wheat head to get kernel counts. All that could be seen were what looked like tiny orange worms. He called Jeff Wade, manager of the CHS fertilizer plant in Kalispell, who helped him identify the midge, which as both larva and winged adult is bright orange.
"Usually when you see an insect problem, you have some time to react," Brosten said. "With the midge, by the time you see it, it may already be too late. You have to be looking for it based on past problems"
Brosten and Wade called in Bob Stougaard, a scientist at Montana State University's Northwestern Agricultural Research Center at Creston.
"We went out and inspected several fields around the valley," Stougaard said. "Fields that would have easily gone 80 bushels per acre were zeroed out. There was no grain in the heads at all, just little orange maggots."
When Stougaard called MSU entomologist Dave Weaver, Weaver connected the dots to a previous call.
"A few years ago I had an isolated call about sticky orange material on a working combine and on the harvested grain. Now I think it may have been the midge larvae being broken up by the harvesting equipment." That would happen, Weaver said, if there wasn't enough moisture for the immature midges to move out of the heads and drop down onto the soil to burrow in to overwinter.
"At grain maturity, the larva need rain or dew to trigger the movement out of the wheat head and into the soil to get ready to form cocoons below the soil surface to get through the winter," Weaver said.
The midge can exist at low populations for several years before the right conditions let their numbers increase enough to become a problem. Wade, too, began putting together information from the past that could have been indications of midge populations increasing to problem levels.
"As we look back on the grain that was coming into our elevator, we've been seeing some of the orange wheat blossom midge symptoms for the last five or six years," Wade said.
Those symptoms can include an appearance similar to frost damage, premature sprouting when there is no rain to promote sprouting, and low falling numbers, which is a measurement the elevator takes to determine the milling quality of the grain.
The extent to which the kernel is damaged depends on the number of larvae present and when feeding begins relative to kernel development, Stougaard said.
Brosten said he will be changing field management to reduce the orange wheat blossom midge, including crop rotations that will include a pulse crop and barley. However, the biggest change will be simply watching for the midge now. At the family farm near Kalispell and on another farm near Fairfield, Brosten will be scouting for the midge at the start of wheat heading.
Local scouting typically includes field surveys at dusk and might someday include midge traps, says Weaver. He currently considers the traps of more use for research.
"The relationship between midge numbers and crop damage needs to be developed for this particular population," he said. The tiny insects can be hard to see clearly in the traps and probably would need to be sent to MSU's Insect Diagnostic Laboratory for identification, eventually. Weaver said the short length of their flight period and sending them off for identification might not allow for timely treatment of fields, but could be the basis for future efforts.
Of more timely use would be soil samples to look for midge cocoons.
"We took soil samples this fall from several fields, and in a couple of soil samples the numbers were way off the charts," said Stougaard. The insect doesn't discriminate among soil types.
"The soil samples give us an indication of what problems might lay ahead, but high cocoon numbers don't guarantee an outbreak. You need to have the correct soil temperature and moisture conditions to drive its development from cocoon through pupae to adult", Stougaard said.
In the near future, midge-resistant wheat should be available, said Luther Talbert, the Montana Agricultural Experiment Station spring wheat breeder at MSU.
"Canadian researchers have developed the marker for a gene that gives wheat resistance to the midge," Talbert said. "Assuming the resistance gene is effective against Montana races of the midge, we can go fairly fast to transfer the gene into a variety that is otherwise adapted for Montana. We should have the gene transferred into otherwise good varieties within two years, but it will still take a couple of years after that to get the seed increased for growers. We need to do the breeding work alongside the entomology work to make sure the gene is effective. However, it's really nice that we don't have to start from ground zero to develop a new variety like we would have had to 10 years ago."
For more details on the orange wheat blossom midge, see an article at: http://www.montana.edu/cpa/news/nwview.php?article=4516