Soybean growers should be watching for leaf defoliation
Nebraska soybean growers may be noticing soybean defoliation in their fields. The culprit is most likely grasshoppers and/or bean leaf beetles, University of Nebraska-Lincoln specialists say.
Numerous reports have come in about grasshopper populations building along field edges and bean leaf beetle populations building in some areas of the state, mainly in the south, said Tom Hunt, UNL entomologist at the Haskell Agricultural Laboratory near Concord.
"With the bean leaf beetle populations growing, soybean growers will likely begin to notice soybean (leaf) defoliation," Hunt said.
Defoliation is the most common type of insect injury observed by Nebraska soybean growers and can occur from emergence to harvest, he said.
While there are several insects that defoliate soybeans in Nebraska, such as the bean leaf beetle, imported long-horned weevil, grasshopper, woollybear caterpillar, thistle caterpillar, green cloverworm, and a few others, rarely does any single species do enough harm to cause economic damage, said Keith Jarvi, UNL Extension educator in Dakota, Dixon and Thurston counties.
"However, the combined injury of two or more defoliating insects can result in economic damage," Jarvi said.
In 1997, entomologists observed combined defoliation from grasshoppers and bean leaf beetles that reached 50 percent in reproductive-stage soybean near Mead.
"When this occurs, soybean growers need to take several things into consideration," Hunt said.
More information, including specific recommendations, is available in the latest edition of Crop Watch, UNL Extensions crop production newsletter, at http://cropwatch.unl.edu/.
"When it comes to treatment and pest management decisions, a crucial consideration is the size of the remaining soybean canopy and the stage of growth the soybeans are in," Hunt said.
If treatment is warranted, identify the defoliating insect or insects and use the insecticide guides found at the Entomology Department's website at http://entomology.unl.edu/instabls/soydefol.htm. Most commonly used foliar insecticides are effective against most soybean defoliators.