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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. Stunting and nutrient deficiency symptoms attributed to sulfonylurea carryover injury in corn.

Damage from herbicides applied in 2011

Many producers have experienced damaged crops this year due to carryover from herbicides they applied in 2011. Dr. Aaron Hager, University of Illinois Weed Scientist, has said that he has seen more carryover herbicide injury this year than in the past 10 years combined.

Why might this be? Herbicides with residual activity often have a rotation interval specified on their respective label. This rotation interval is the minimum period of time that must occur between herbicide application and planting of the rotational crop. This is based on the average rate of herbicide degradation which is influenced by soil moisture, pH, microbes and other factors. Degradation takes place by several pathways, including a chemical process called hydrolysis or microbial degradation. Environmental conditions, such as dry soils or high soil pH, can dramatically slow herbicide degradation, which increases the probability that herbicide residues will persist longer than normal. Conditions such as drought, nutrient deficiency, high salt, disease and insect pressure may increase susceptibility of non-labeled crops to damage.

I will use an example to illustrate this principle. A grower in the Western IL crop reporting district planted soybeans in 2011 in early June. He applied a sulfonylurea herbicide at planting. He then planted corn during mid-April this year and began noticing symptoms of herbicide-damage soon after emergence. Symptoms can include stunting, bottle brushing of roots leading to above-ground nutrient deficiency symptoms, and chlorotic banding across leaves. He planted right outside of the rotation interval and yet experienced significant damage (Figure). Why? There may be multiple reasons: 1) 2011 was a very dry growing season and this spring has also been dry, sulfonylurea herbicides require water in order to undergo the degradation process of hydrolysis, 2) even with an adequate water supply the higher the soil pH, the slower the degradation, 3) some plants in the field were also experiencing symptoms of seedling blight caused by soil-borne plant pathogens.

Carefully following label directions with special attention to rotation intervals can help to decrease risks of herbicide damage on crops in most years.



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