Spider mites are destroying soybean fields already hit by drought, a University of Missouri entomologist told a meeting of certified crop advisers (CCA) at MU Bradford Research Center.
Anyone with soybeans should be scouting their fields closely every day, said Wayne Bailey, MU Extension pest management specialist.
"If you are not getting down under the plants, the first thing you may see are bean leaves changing color," Bailey said. "Dying plants first take on a grey cast, then yellow. After that the infested leaves bronze and fall off."
Left untreated, soybean plants die.
"The two-spot spider mites live in grass, but move into the edge of fields and work their way across," Bailey said. They start from roadside grasses or from grass waterways that cross the fields.
"I'm getting most calls from northwest and northeast Missouri," Bailey said. "There's a lot of spraying going on."
The spider mites are so tiny they are almost impossible to see without a microscope. They stay on the underside of the leaves, so you must look there, Bailey said.
"A common scouting method is to lay a sheet of white paper under a leaf, then tap the top. If tiny yellow specks drop onto the paper, you have spider mites. You must look close to see the black spot on each side of the body."