OREGON COUNTY -- The Alfalfa weevil is once again living and growing in area alfalfa fields.
Vance Hambelton, University Extension agronomist, said, "I was told by an Oregon County alfalfa producer March 22 that he had found a weevil in his alfalfa. Then a producer told me on March 25 that he had alfalfa weevils. I was in a new alfalfa field the next day near Bakersfield and the weevils were even starting to do damage there."
Hambelton explained that alfalfa weevil is a destructive insect which prefers the alfalfa plant for its food and reproduction. It benefits from mild weather during fall, winter and spring seasons. He said when temperatures rise above 50 degrees for several consecutive days during these seasons, adult weevils will deposit eggs in the stubble of alfalfa plants. Hambelton said in a typical year a majority of weevil eggs are laid during the spring a few weeks before they are commonly seen in early to mid April.
"The larvae hatching from eggs in the old stem are small yellow, green or brown worms with shiny black heads that crawl to the growing terminal and start feeding. He said after several days of feeding, the larvae become light green in color with a white stripe down the middle of the back. The larvae, for three to four weeks, depending on temperatures, gradually working their way to newly opened leaves and then to older foliage. Hambelton said this feeding consists mainly of eating the green from the leaf surface and leaving a skeletonized grayish white leaf.
Hambelton warns producers that they should keep close watch for damage to determine when control, if any is needed
Two years ago much of the alfalfa crop in the county was lost due to the weevil.
The Oregon County University of Missouri Extension Center at Alton has several guide sheets available on the alfalfa weevil problem.