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Deal with vining weeds at harvest

Here’s advice for how to ease harvest now and prevent weeds like morningglory and burr cucumber next year.

Tom J Bechman 1

August 22, 2022

2 Min Read
morningglory flower peeking out from cornstalks
NOTHING PRETTY HERE: Don’t let anyone convince you that the morningglory flower peeking out from behind the corn plant is pretty. It signals potential problems at harvest. Bill Johnson

One thing ag machinery companies have not yet developed is a husking roll or grain platform that handles morningglory and burr cucumber without missing a beat. From the days of two-row mounted corn pickers until today, a crop covered with a patch of morningglory or burr cucumber makes the farmer in the driver’s seat cringe. Some combine makes and models handle these vining weeds better than others, but none earns a gold star.

“This is the type of year when my phone starts ringing before harvest and stays busy,” says Bill Johnson, Purdue Extension weed control specialist. “It was wet early, then hot and dry for a long time in many areas, then wet again with on-and-off showers through August.

“Morningglory likes hot, dry weather. Burr cucumber prefers stretches with showers where soils stay moist. We’ve had all those conditions somewhere in Indiana this season.

“People want to know what they can do to simplify harvest if they’ve got patches of these in their fields. Fortunately, there are options to use herbicides as a dessicant to dry up weeds to get the combine through the field.”

The 2022 Ohio, Indiana and Illinois Weed Control Guide lists possible harvest aids for both corn and soybeans. Mark Loux of Ohio State University and Aaron Hager of the University of Illinois worked with Johnson to assemble these recommendations.

Options for drying up weeds and vines in corn shortly before harvest include 2,4-D, glyphosate, Gramoxone, Aim/Longbow, dicamba and Liberty. Timing for application and preharvest intervals vary and are spelled out on labels. For many products, corn must reach black layer before they can be applied.

Options for drying up weeds and vines in soybeans as a harvest aid include the same products. Check labels for application timing and harvest intervals specifically for soybeans.

Controlling vines next year

Since both morningglory and burr cucumber are annual weeds, going after them in the fall as you might Canada thistle isn’t an effective option, Johnson says. Annuals tend to shut down naturally later in the fall and aren’t actively growing and taking in products.

“In fields where you know you have morningglory and burr cucumber, apply your residual herbicide next spring as late as you can,” Johnson advises. “This is one situation where it pays to apply a residual later.

“Another key is splitting your residual application and applying more residual herbicides when you make the post application. These weeds germinate late and continue to germinate, so you want residual product to last as long as possible.

“If you’re spraying escapes or late emergers post, spray while weeds are small. You want them to be 4 inches tall or less, and 2 inches would be better. You must be vigilant against these vining weeds.”

About the Author(s)

Tom J Bechman 1

Editor, Indiana Prairie Farmer

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