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Angie Peltier

Angie Peltier
Former Extension Educator, Commercial Agriculture

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Hill and Furrow

Current topics about crop production in Western Illinois, including field crops research at the NWIARDC in Monmouth.
Figure. Soybean seedlings suffering from PPO-inhibitor herbicide injury.
click image to view 2 more

Herbicide injury in soybean

Very few soybean acres have been planted at the Northwestern Illinois Agricultural Research and Demonstration Center (NWIARDC) in 2013. For one soybean field that was planted on May 17th, emergence on and around May 29th coincided with heavy rain events.

Unfortunately the emerging soybeans in this field began to develop severe symptoms soon after emergence. Symptoms were dramatic and began with discolored seed leaves (cotyledons) (Figure). Symptoms were also evident on unifoliate leaves as they emerged and extended, and included deformed, discolored, and tattered leaves (Figure).

Herbicides called PPO- (protoporphyrinogen oxidase) inhibitors can cause significant seedling damage when rain mixes these chemicals into a solution that bathes seedlings in the herbicide as they emerge. Ideally, PPO inhibitors would be applied approximately 2 weeks before planting – close enough to planting to kill weeds that will compete with emerging soybean seedlings and far enough from planting to dissipate a little before seedling emergence. Dr. Aaron Hager, Weeds Extension Specialist with the University of Illinois, has indicated that large rain events that coincided with soybean seedling emergence have resulted in widespread PPO-inhibitor herbicide injury throughout Illinois in 2013.

Agricultural professionals have begun to expand their chemical arsenal to combat weeds that have become resistant to some of the most widely used herbicides. Before the advent of herbicide tolerant varieties and hybrids, herbicide injury was something that was just considered a cost of doing business in some years. We will need to remain vigilant to carefully follow label directions to continue to minimize the chance of significant injury occurring.

There is positive news in the affected soybean field at the NWIARDC – growth has resumed and more normal-looking trifoliate leaves are beginning to unfurl.

For more information and pictures, a 2009 publication entitled, "Practical Weed Science for the Field Scout: Corn and Soybean" published by the University of Missouri Extension is good resource that can help in diagnosing herbicide injury in corn and soybean.

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