Renewable Farming

The dicamba damage dilemma multiplies as states extend cutoff dates for spraying

One of our Indiana clients texted late yesterday: “This season it’s easy to tell who planted dicamba beans. Those are the only ones not all puckered up. It’s a seed monopoly — the only kind to plant if you don’t want clobbered beans.”

July 18, 2019 — Our Indiana client followed up by detailing that “one reason we have so much dicamba damage here on several types of crops is that we have so many prevented plant fields. Many farmers presume that cutoff dates for spraying dicamba don’t apply to unplanted fields, so spraying continues even though nearby crops are vulnerable.”

Light dicamba damage on soybeans which are not
dicamba tolerant. Other crops are showing damage too

He cites an Purdue Ag Extension recommendation which encourages dicamba spraying for prevented-plant fields. Nowhere in that report do we see any cutoff dates. Here’s the advice from Bill Johnson and Marcelo Zimmer:

A farmer reading their weed control advice might conclude it’s okay to spray dicamba formulations on prevented plant weeds regardless of date. 

Dicamba injury reports began arriving at state weed control regulators more than two weeks ago. Farmers in several states with severely delayed planting (which include the majority of soybean acres) have appealed with officials to extend dicamba spraying cutoff dates. Thus the damage on earlier-planted crops is showing up now.

DTN staff reporter Emily Unglesbee has a detailed update at this link:

Soybean breeders have no way to defend against dicamba vapor.  The link below takes you to a National Public Radio report on dicamba injury on experimental soybean varieties at the Fisher Delta Research Center at Portageville, Missouri. Research scientist Pengyin Chen has been seeing damage in his foundation seed soybean plots the past three years. Stations like this build the genetic base for new commercial strains of soybeans. None of his experimental beans are are dicamba-tolerant.

NPR writer Dan Charles quotes Pengyin Chen: “Chen’s biggest worry is that drifting dicamba is making it impossible to carry out public research on soybeans here in Portageville and perhaps in other places, too. (It also makes farmers less interested in planting public varieties, since they’re vulnerable to dicamba drift.)

“If you kill the public research programs, who is going to study disease resistance, or stress tolerance?” Chen asks. “Those efforts are going to be gone.”

July 29 update on this subject from GMwatch is at this link:


Chen measures damage from dicamba and other foliar herbicides by
planting commercial varieties tolerant to specific chemicals such as
dicamba and glyphosate. On the right is a dicamba-tolerant variety.
On the left, a non-GMO experimental bean which shows injury.
Photo by Dan Charles