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Blistering soybean leaves vs. cupping: the first isn’t a worry, the second is

Manitoba Agriculture’s Lionel Kaskiw is getting calls about dicamba drift

If you see what looks like blistering on soybean leaves don’t worry it’s not herbicide drift and the crop will grow out of it, says Lionel Kaskiw, Manitoba Agriculture’s Farm Production Advisor based in Souris.

However, leaf cupping can be a sign of dicamba damage in soybeans that are not dicamba-tolerant, he said July 26 during the CropTalk Westman webinar.

“We’ve been noticing this (dicamba damage) a lot more in the Red River Valley, where we are seeing a lot of the Xtend (dicamba-tolerant soybean) varieties being grown and producers are… spraying dicamba on their soybeans and (it’s) drifting on to other fields that are not the Xtend varieties,” Kaskiw said, adding he has been getting calls about dicamba drift since July 20.

In severe cases the damage shows up on the new plant growth as it grows. he said.

“In lighter cases where you go farther out into the field where the drift isn’t as bad you will see some damage and the plants may out grow it.”

A lot of soybeans are flowering now and have been for a week or so. That’s when dicamba drift can cause the most yield damage, Kaskiw said.

Kaskiw also said those spraying roadsides and ditches need to be more aware of nearby crops, especially soybeans because some of the weed killers used in ditches also kill soybeans.

Dicamba drift injury on non-dicamba tolerant soybeans causes leaf cupping, says Lionel Kaskiw, Manitoba Agriculture’s Farm Production Advisor based in Souris.
photo: Lionel Kaskiw, Manitoba Agriculture

Monsanto recommends applying dicamba with nozzles that produce coarse to ultra-coarse droplets such as Turbo TeeJet Induction and Air Induction. Those nozzles require application rates of at least 10 gallons of water an acre.

Spraying should take place when wind speeds are three to 15 kilometres an hour and at sprayer travel speeds of no more than 24 kilometres per hour. Boom height should be no more than 50 centimetres, Monsanto says.

Farmers shouldn’t spray during inversions or when wind conditions are dead calm.

Cleaning all the dicamba out of a spray tank isn’t hard, but critical.

Monsanto recommends triple rinsing sprayers after applying dicamba. The first rinse is with water. All filters and screens should cleaned with in an ammonia or detergent based solution. The tank should get a similar solution and be agitated then flushed. Follow that with a third rinse with water.

As for the bubbling on soybean leaves, that’s occurring in some areas where there’s good soil moisture and plants are growing faster than the leaves can keep up.

“It will out grow this in a few days as the leaves start to get their full development,” he said. “You have extra growth in between the veins here and you see the bubbling affect. As the leaves get bigger these will disappear.”

About the author

Reporter

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.

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