Corn School: How severe weather can influence herbicide injury


What happens when a soil-applied herbicide application is followed by severe weather?

For many herbicides it is business as usual, but in some cases a heavy rain can cause a typically safe product to injure the plant.

On this episode of RealAgriculture’s Corn School, Ontario Ministry of Agriculture, Food and Rural Affairs weed specialist Mike Cowbrough shares a case study comparing how a herbicide can perform when no rain follows application versus a situation where two inches of rain follows just days after the sprayer has left the field.

We caught up with Cowbrough at Southwest Crop Diagnostic Days at the Ridgetown College campus, University of Guelph where he looks at a corn plot that received no rain after herbicide application — it boasts a strong population of healthy, green corn plants. But beside it is a plot that received two inches of rain after application. Here, the flush of water moved the herbicide into the soil profile causing leaves to exhibit white, yellow and brown leaf bleaching injury.

In this case, however, Cowbrough cautions growers not to panic. He notes that the injured plants are already showing green, healthy new growth and in two to three weeks it’s likely little evidence of the injury will remain. He says the injured plants have simply suffered an overdose caused by the excess moisture and will recover as the season progresses.

In the video, Cowbrough also tours soybean plots to look at why it’s important for growers to know the herbicide soybean system they are utilizing in their fields and what can happen when they spray the wrong herbicide on herbicide tolerant varieties.

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