Why weeds have been so difficult this year

Weather may be causing weed control problems.

I’ve heard it more than once, weeds just aren’t dying this year. The herbicide system doesn’t seem to matter. Is it resistance to herbicides? I hope not!

Disclaimer: Following are my un-proven, non-scientific thoughts.

First off, it’s linked to 2015. Last year’s chemistry washed below weed seed germination level. Normally, some sort of residual chemistry is used in a producer’s program. I think it’s safe to assume that some amount of that chemistry remains in the soil profile for an extended time (i.e. longer than the crop season the product is applied) before it is completely broken down. We don’t consider this as part of the program, but I wonder if it doesn’t normally help control a portion of new weeds the year following the application.

There is simply more weed seed out there. All the rain last year was terrible for getting all the applications made and getting products to work. Because of this, many fields didn’t get an in- crop application, which led to dirty fields and a build-up of weed seed in the soil bank. Weeds are much more prolific at reproducing than desirable crop are.

2016 hasn’t helped us much. Though we jumped off to a great start, it turned cool, then dry. With the cool weather, weeds didn’t take up the chemicals as well as normal. The dry conditions failed to provide the .5” or so needed to ‘activate’ chemicals applied this spring which work in the root uptake zone. After all that, we were then trying to kill weeds that had previously been damaged. Those weeds didn’t take in the chemicals well either.

So, what can we do for an easier 2017? At this point not much. Control has not been bad, but not what we want. As I stated earlier, these problem weeds are so prolific, any is too many. In the future we will consider different chemistries and combinations of chemistries. We already plan two passes, but for some difficult weeds we may have to plan three passes. Grass escapes have disappointed us this year, but for us, the most difficult weed we have is bur cucumber. It is very trying because it germinates all summer long, even into August. Cucumber vines can cover 20-30 feet. It crawls across the top of corn plants, and the combine hates it! Shown in its name, it has burs, not much fun to untangle from any equipment.

It’s likely we will make an aerial application to some fields if for nothing else sanity and ease of harvest.


The opinions of the author are not necessarily those of Farm Futures or Penton Agriculture.

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