HERBICIDES applied in a highinput environment do not cause plantstressassociated yield losses if applied at the appropriate time

HERBICIDES applied in a high-input environment do not cause plant-stress-associated yield losses if applied at the appropriate time.

Can herbicides stress high-yield corn?

Corn growers, finish over-the-top weed control programs before the V5 stage of growth, particularly in high-input, high-yield situations.

Growers in Alabama, Florida and Georgia planted 725,000 acres of field corn in 2014.  With recent price levels hovering somewhere between $3.50 and $4.50 per bushel, 2015 corn plantings in this region will likely be lower.  Regardless, there will be many growers still striving to break the 250- or 300-bushel plateau. Hopefully, you have already heard that one of Georgia’s own recently crushed the record book with a yield of 503.7 bushels per acre.

Eric Prostko

When I talk to high-yield corn growers, the two things that I here consistently are that all stresses must be managed (as much as possible) and timeliness is everything.  The most common stresses associated with high yield corn production are light, heat, moisture, nutrients, insects, and disease.  Well, what about herbicides?  Do they cause undesirable plant stress in a high input environment?  That’s the million dollar question that I have been asked over the past few years and the subject of some of my current weed control research efforts.

I must say that up until a few years ago, my answer to this question would be that I do not know since I have never been able to consistently produce corn yields in excess of 225 bushels per acre.  Although my goal is always to produce the best crop possible, my yields are often limited by my inability to irrigate on a timely basis and/or spray fungicides on tall corn grown in a confined research area.  

It is challenging for me to be a high-yield producer because I spend most of my day driving to and from research plots, troubleshooting field problems (writing Pulitzer Prize winning popular press articles such as this) and answering countless phone calls, texts and e-mails. After all, I am an Extension specialist first.

In 2013, I was fortunate to grow corn that produced over 270 bushels per acre (dumb luck) in a couple of trials, so I was able to collect some data that was very positive in terms of corn safety. 

In 2014, I conducted an on-farm test in a high-input environment evaluating several popular herbicide programs.  Yield results from this test are presented in Table 1.

The good news is that there were no statistical yield differences between the non-treated check and any herbicide treatment. Yield averages were slightly lower than 300 bushels per acre in this test due to the fact that it was located in a wet area of a terrace. A PowerPoint presentation with the complete results is available at www.gaweed.com.  I will be repeating this and other high yield tests in 2015.         

In summary, it would appear from the results that I have from a few trials conducted in 2013 and 2014 that herbicides applied in a high-input environment do not cause plant-stress-associated yield losses if applied at the appropriate time.  However, I would encourage all growers to be finished with their over-the-top weed control programs before the V5 stage of growth.  Herbicide applications made during this time are likely to be much more effective due to the fact that the weeds will be smaller and thus more sensitive to herbicides. 

Additionally, spray coverage will be improved because the corn canopy will be less imposing.   Remember, the risk for herbicide related yield losses has the potential to increase if applications are pushed closer to and/or during critical reproductive stages of growth.  I hope you have a very productive corn growing year in 2015.  As always, good weed hunting!

TAGS: Management
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