Some early emerging soybean crops are getting a rude initiation from a harmful pest.
"Emerging plants may serve as 'trap crops' for bean leaf beetles," says John Obermeyer, Purdue University entomologist. "Beetles that overwintered successfully are seeking both wild and cultivated legumes to feed on. Several people have observed and reported bean leaf beetle feeding in early planted fields and plots, but none have been treatable levels."
The most critical crop stage for soybean damage from pests is from emergence through the establishment of the first trifoliate.
"Extensive cotyledon damage is cause for serious concern," Obermeyer says. "If cotyledons are being destroyed before the unifoliolate leaves fully emerge, or if the growing point is severely damaged, reduced yields are likely. However, once trifoliate leaves have unrolled, soybean can tolerate up to about 40 percent defoliation without yield loss."
Obermeyer advises producers to scout their early emerging soybeans for bean leaf beetles.
For more information and a treatment threshold table, refer to the April 28 Purdue Pest and Crop Newsletter. The newsletter is available online at http://www.entm.purdue.edu/Entomology/ext/targets/p&c/index2006.htm.
Additional soybean management tips can be found at Purdue's Cool Bean Web site, located at http://www.coolbean.info.