Soybean Leaf Cupping

The following question was sent to the P&PDL diagnosticians here at Purdue University:

Question: Do you have any answers or theories to the cause of cupping soybean leaves? We keep hearing that it is banvel drift but there are no patterns to this effect. It is stopping at field boundaries and appears to not have any variety enhancement. Any information to this that you have will be of great use.

Answer: The following information was provided by Dr. Tom Jordan, Weed Science Specialist. Leaf cupping of soybeans has been wide spread through the Midwestern states this year. If the field does not show a drift pattern which is associated with an application to a near by corn field, then there are two possibilities which may explain the injury. First, the sprayer used to apply the soybean herbicides was not cleaned with a solution which removed all of the growth regulator herbicides used in corn and caused the injury, or secondly, the environmental conditions at the time of application was such that the mixture of herbicides and additives( i.e. crop oil and fertilizer or salts) caused the soybeans to show leaf cupping. Usually the injury from these factors will grow out of the symptoms in a few days to a few weeks without causing any yield loss. The injury from the environmental stress will usually grow out faster than the injury caused by a herbicide contamination problem.