Don’t take 2,4-D drift lightly

Anyone who has sprayed 2,4-D knows it can drift and injure soybeans. Within two to three years, Dow AgroSciences hopes to introduce 2,4-D-tolerant corn, meaning 2,4-D may become popular again.

It’s time to brush up on minimizing drift when applying 2,4-D, notes Bill Johnson, Purdue University weed control specialist. “Past studies indicate an average of 16% of 2,4-D applied goes off-target,” he notes. “It’s often caused by spraying when it’s too windy, using the wrong nozzles, setting pressure too high or running booms too high.

“There’s also times when it’s just flat-out misapplied. Maybe you pick the wrong rate. These are all things you can work on to make sure you spray accurately and minimize drift.”

Key Points

• More 2,4-D applications are likely once 2,4-D-tolerant crops are approved.

• Drift results from not paying attention to details.

• “Just a little drift” can become thousands of dollars of lost yield.

Injury equals yield loss

Soybeans at the V5 (vegetative) stage show more injury at lower drift amounts than soybeans at the V2 stage, Johnson notes. Soybeans injured by drift at the R2 (reproductive) stage recover quicker, but the yield loss is more dramatic than if the beans were injured earlier.

The degree of injury depends upon the amount of drift. Weed scientists spray various diluted rates on soybeans at various stages to simulate drift. Symptoms vary from dark green, cupped leaves to stunted plants.

Just how expensive is drift? Suppose there’s enough drift at the V5 stage to cause 10% yield loss. If base yield is 50 bushels, you lose 5 bushels per acre. At $8 per bushel, that’s $40 per acre. It’s a $20,000 mistake on 500 acres!

Odds are drift injury won’t be uniform. Some plants may be impacted more than others. The best advice is to avoid drift in the first place, Johnson concludes.

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GROUND ZERO: Here are soybeans in the V2 stage not affected by 2,4-D drift. Andy Robinson, Purdue University


DRIFT DISASTER: These soybeans were hit by a healthy shot of 2,4-D drift (140 grams/hectare) at the V2 stage. Andy Robinson, Purdue University

This article published in the March, 2010 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.