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What you need to know about dicamba for 2018

John Deere sprayer
PARK IT? Will your sprayer be parked more than it is operating as you try to comply with the dicamba label in 2018?
Purdue weed scientist addresses questions after EPA announces dicamba herbicide label changes.

The dust has hardly settled on complaints due to injury from dicamba applications in 2017. Before harvest was even over, EPA worked with the companies that offer dicamba products and announced label changes for 2018.

Bill Johnson, Purdue University Extension weed control specialist, and Joe Ikley, Purdue weed science program specialist, took a closer look at properties related to dicamba herbicides. This was the first year they could conduct studies on drift and or volatility.

Johnson explains what the EPA changes mean in this exclusive interview with Indiana Prairie Farmer.

What specific changes did EPA make for these products concerning application conditions? First, EPA reduced the maximum wind speed at which these products can be applied. The label will now read “3 to 10 miles per hour.” EPA also introduced language that says application can’t be made if there is any measurable wind speed at all next to sensitive crops.

What other restrictions were added? The products can only be applied between sunrise and sunset. EPA did not issue a cutoff date during the season for spraying, although at least one state, Arkansas, has done so,

What other changes did EPA make? EPA declared that dicamba products are now restricted-use products. That means you must have a pesticide applicator’s license to purchase and apply the product. EPA also will require mandatory training for anyone applying dicamba products in the future.

In Indiana, this means that PARP [Private Applicator Recertification Program] classes for continuing education credits toward renewal of your pesticide license will be about dicamba application in 2018.

Will these changes make a difference in 2018? We hope they will emphasize the importance of following the label to reduce off-site movement. However, they will make it even more difficult to find a time to apply dicamaba postemergence and stay completely on label. We don’t get many extended time periods during spraying season during those hours when wind speed will qualify.

EPA also announced that if rainfall is forecast within 24 hours, you’re not allowed to spray. Trying to meet all those guidelines to stay on the label will be extremely difficult.

What did you discover when applying products this year? We had situations where the product moved from the field where applied to off-target vegetation up to three days after application.

Volatility is when vapor moves. Drift is when physical particles move. Some of the off-site movement is being blamed on dust particles with dicamba on them and movement in runoff water after a heavy rainfall event. Any way you look at it, the difference between these different types of movement can be hard to distinguish without good research and some effort in understanding the pattern of injury.

Where does all this leave the grower for 2018? If you have Xtend soybeans and follow the label the best you can, that’s about as good as you can do. However, if you know you have fields of soybeans or other sensitive crops which will be near Xtend soybeans, you may want to figure out other options for those fields besides applying dicamba herbicides.    

TAGS: Weeds
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