The top 10 pesticide application mistakes

Late-night television host David Letterman is retiring soon, but hopefully the “Top 10” lists that he has made so popular will continue. Here is our attempt to keep them going with our Top 10 mistakes made when applying pesticides.

10. Spray system setup. The wrong spray system setup will cause uneven spray coverage and failure to get pesticide uniformly deposited where it is need. Sometimes you have to adjust your spray setup to the ingredient being applied. For example, complex tank-mixtures, changing spray volume and adding ingredients such as oils can increase the number of fines and cause spray drift if you keep your spray setup the same.

9. Misidentification of pests. Identification can be difficult, but it is important and someone needs to take time to do it correctly. On the bright side, misidentification of pests is better than misidentification of the crop. The proliferation of new herbicide-tolerant (HT) crops and their lack to tolerance to herbicides used in other HT systems can mean total crop loss. Let’s hope misidentification of crops does not make this top 10 list next year.

8. Not knowing targeted pests are resistant. This is becoming an increasingly big problem as resistance to herbicides, insecticides, and fungicides spreads. If you are sure you applied the pesticide correctly, you probably did and the surviving pests are likely resistant. Get surviving pests tested as the sooner resistance is identified, the easier it is to manage.

7. Applying the wrong rate. Sometimes rates are too high and cause crop injury, but the problem is usually applying too little to save money. The consensus among experts is that low rates encourage the evolution of resistant pests, and that can have a huge, long-term economic impact. Think of it as an antibiotic prescription that you get from your doctor: Take the full dose.

6. Mixing errors. Follow the label mixing directions for your pesticides and other chemicals. A specific sequence and strong agitation are often required. Remember that it is much easier to prevent tank mix problems than to cure them after they occur.

5. Spray system cleanout. Depending on the pesticide and crop being sprayed, residues in your tank, spray lines, and nozzles can unexpectedly severely injure crops in later sprays.

4. Inactivation of the pesticide in the tank. Tank-mix conditions are often complex and the trend is for it to get more complex, particularly in low spray volume aerial applications. Hard water ions and micronutrients can totally inactivate glyphosate and other pesticides. In addition, many products require a specific pH to ensure the pesticide is stable and performance is not reduced. Water conditioners and compatibility adjuvants are often necessary.

3. Waiting too long to apply. A common mistake is to apply at the wrong stage, when pests and weeds are too big or dormant. A common joke is that everyone thinks knee-high weeds meet the label requirement to be 6 inches or less. The pesticide often still works when all the other conditions are favorable, but applicators are risking product performance when any conditions are unfavorable. And most importantly, growers are losing yield the longer they wait to control your pests.

2. Applying under the wrong environmental conditions. Pesticide labels often have specific temperature, humidity, rain-free interval, and plant stress restrictions, as well as wind speed limitations. Never apply when the wind speed is too high or low, as some air mixing is needed to prevent an inversion.

1. Not applying the right adjuvant. OK, this is not from a scientific survey and maybe you don’t think adjuvants should be number one, but we are adjuvant guys and we see it that way. You have to admit, high-quality adjuvants are important!

For more information on adjuvants and aerial application, contact John Garr at 765-395-3441, or visit



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