Agrochemical Compatibility

— Written By

Lots of questions about mixing agrochemicals. I have been preparing a summary for the APRES meeting on a student’s work where he mixed up to 5 components (herbicides, fungicides, insecticides, micronutrients, etc.) There is no way to give you a simple answer. But, here are a few points.

Grass control with Select (clethodim) gets reduced consistently by Headline, Bravo, and Abound. Other materials typically do not reduce efficacy. Most growers are not going to want to spray sequentially, so if they do mix these I would increase the Select rate, say from 8 oz/acre to 12 oz/acre. We have not seen problems with boron and manganese in most instances when mixed with Select.

Most broadleaf herbicides like Cobra, Blazer, Cadre, and 2,4-DB will work okay when mixed with fungicides. We occasionally see an issue but it is inconsistent and generally not a major loss in control.

Of course, activity of Select will be reduced by Basagran, Blazer, Cobra, and to a degree by Cadre but generally not by 2,4-DB. I wouldn’t mix Select with Cadre…just wait and see if the Cadre kills the grass…many times it will.

Some people can mix boron and manganese together and not see a problem…others see a problem. Make a slurry with each material separately (especially if you are using dry materials) and make sure they are in solution before combining in the tank. That is half the battle. Sometimes manganese and 2,4-DB do not mix well, but this too can be inconsistent. Getting a little less control with mixtures isn’t so bad, but cleaning out 50 acres worth of material in a tank is an issue. Water quality (pH, hardness, softness, etc.) most likely influences these interactions, so growers ought to go slowly when mixing, especially when doing 3 or more components.

When we start spraying materials that control stem rot we need to keep in mind that herbicides generally call for adjuvants (crop oil or 80/20 surfactants) and these increase leaf penetration or “hold” materials on the leaf. This is not what we want to happen with fungicides designed to reach the crown of the plant. Growers need to keep this in mind as well.

Apogee requires nitrogen and crop oil to perform well. Because the grower is spending a lot on Apogee already, I would apply Apogee without other agrochemicals and “get it right.” BUT, do not leave out the UAN and crop oil.

As folks start spraying manganese and boron remind them to look at what products deliver. We have a short write up on this in 2011 Peanut Information. We are paying for a lot convenience and very little micronutrients with some of our products.

Some growers have started experiencing nitrogen deficiencies due to poor nodulation. This is painful. If a grower has a nitrogen deficiency and poor nodulation or no nodulation (yellow plants,) it takes 500 to 700 pounds of ammonium sulfate per acre to correct this. Yes, this is expensive but there is no way around it. See 2011 Peanut Information for more details.

I’ll try to send a few more comments next week.

Article first appeared as North Carolina Peanut Note (PNNC-2011-017)