Herbicides not always to blame for crop damage

Herbicides not always to blame for crop damage

Herbicide labels will never make the New York Times Bestsellers List, but do contain good information to prevent herbicide injury. Many problems frequently blamed on herbicides can only be addressed before planting.  Issues such as low soil pH, high Zinc, and nematodes need to be remedied before the problem is observed in the field.

More often than not, my troubleshooting calls begin with the phrase, “Something is wrong with my crop. I think I have some type of herbicide damage!” All herbicides have the potential to cause crop injury, especially if the wrong herbicide or wrong rate is applied at the wrong time, or labeled crop rotational intervals are not followed. In my experience, many “herbicide injury” complaints turn out to be something else, though.

Figure 1. Peanut injury caused by low soil pH and high levels of zinc (pH = 4.9, Zn = 46 lb/A). Often confused with Valor damage.

It’s hard to believe that spring planting time is here!  Seems like only yesterday I was harvesting peanut plots.  Although some commodity prices may be unfavorable, the planting season is always a time for renewed hope about the potential to grow a better crop than the previous year.  I am sure that 2015 will also bring new challenges.

One of the duties of an Extension specialist (at least in Georgia) is to assist county Extension agents in troubleshooting field problems.  This can be accomplished over the phone, internet or more frequently in person.  Smart phones equipped with a camera have helped reduced my road time but some problems can only be tackled in person. 

If you think about all the things that can go wrong when growing a crop, it almost seems impossible to grow a crop: hot/cold temperatures, dry/wet conditions, insects, nematodes, diseases, soil fertility issues, seed quality, planting depth, soil compaction, etc., etc.  A farmer has no choice but to be a jack-of-all-trades.  Still not sure how you guys sleep at night!

Many problems frequently blamed on herbicides can only be addressed before planting.  Issues such as low soil pH, high Zinc, and nematodes need to be remedied before the problem is observed in the field (Figures 1 and 2).  The only way to know for sure that you have any of these problems is through proper soil testing. 

Figure 2. Corn injury caused by sting nematodes. Often confused with ALS herbicide injury.

Hopefully, you have taken soil samples this fall/winter, especially if unusual problems were observed in 2014.  Many nutrient deficiencies can be fixed with sidedress or topical applications of additional fertilizer (Figure 3).

Figure 3. Potash deficiency in soybean. Frequently shows up around the time POST herbicides are applied.

Frequently, herbicide injury problems that do occur can be traced back to what happened during the mixing/loading and/or sprayer cleaning processes.  When many herbicide containers are located near the mixing/loading area, it is very easy to grab the wrong jug, especially when in a hurry.  It is also very easy to assume a sprayer is clean or only contains clean water.   I would love to not have to see any more peanuts that accidently got doused with glyphosate!!.

So, as we head into this 2015 crop season with no idea about what challenges may lie ahead, I encourage you to be a good detective when evaluating crop problems.  It is easy to blame herbicides.  It’s not so easy to admit that some other issue, especially one that could have been fixed before planting, is causing the problem.  I strongly encourage you to read the labels of all herbicides you are applying. 

Although, herbicide labels will never make the New York Times Bestsellers List, they do contain a lot of good information that will help prevent herbicide injury.  I also encourage you to pay closer attention to the mixing, loading and sprayer-cleaning processes.  Lastly, if you live in Georgia, contact your local county extension agent for trouble shooting assistance.  He or she will likely be aware of any widespread problems and have direct access to all UGA extension specialists.  As always, good weed hunting!

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