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• It’s difficult to tank-mix more than two materials and make an application at the best time to provide optimum control of the target pests.• Usually tank-mixing requires the grower to determine whether he or she can live with less than complete control of one or more pests.• Sometimes the reduction in control is due to a lack of compatibility of materials in the tank-mix.
April 19, 2012
Sequential treatments are much like ‘cuss’ words to most peanut growers and tank-mixing is too often music to their ears, says North Carolina State University Peanut Specialist David Jordan.
It’s difficult to tank-mix more than two materials and make an application at the best time to provide optimum control of the target pests. Usually tank-mixing requires the grower to determine whether he or she can live with less than complete control of one or more pests, Jordan says.
Sometimes the reduction in control is due to a lack of compatibility of materials in the tank-mix.
But often times it’s a case of you thinking everything is ready to be sprayed at that one time you decide to apply a tank-mix.
In reality, most of the time you are a little early for one thing and a little late for something else.
“As long as the grower understands the tradeoff and can live with the results, tank-mixing can be a good thing,” Jordan says.
Once you get into tank-mixing multiple, especially 3, 4 or 5 products, efficacy becomes a guessing game, and it’s hard to determine which material is doing the job and which one isn’t and knowing exactly what will happen.
Peanut growers have 19 different active ingredients for herbicides alone, plus multiple and different means of application and recommended timing of application.
Insecticides bring another 16 options and there are at least 20 fungicide options. Without adding in Apogee and other specialty products and fertilizers, or multiple application strategies used on peanuts, that brings the total tank-mix options to over 6,000.
In most cases most tank mixes are biologically and physically compatible. Biologically, you are going to control the target pest at some level without damaging the plant.
Physically, these materials will mix smoothly without precipitates forming, stopping up spray equipment or some other physical problem.
However, Jordan says there are some wild cards — water quality such as softness or harness and pH.
Spray volume, adjuvant selection and formulation can also play a role in compatibility. For example, is the formulation of the product more important than the active ingredient?
For example, with chlorthalonil formulations the formulation may have a bigger effect on how well the tank-mixed herbicide works more so than the active ingredient, Jordan says.
Adjuvants can have a big impact on how well one pesticide works versus another material in a tank-mix.
For example, the grower may want a fungicide to move through the canopy to reach the soil-borne pathogen. But mixing a fungicide with a herbicide and the appropriate adjuvant for the herbicide can keep the fungicide on leaves and minimize efficacy of the material.
With herbicides in a tank-mix, timing of application is always an issue. If a grower applies the tank-mix when weeds are small, the loss in efficacy from the tank-mix may not be a big deal.
On the other hand, if the weeds are larger than optimum and the efficacy is reduced, there could be problems with the tank-mix, Jordan says.
Despite many well-documented reasons why tank mixes can be a concern, there are plenty of good reasons to make a single application of multiple products, with savings in time and labor at the top of the list.
Herbicides mixed with herbicides provide the most problems, but there are several tank-mix options that do work, Jordan says.
“Paraquat mixed with Basagran is an example. If you need to reduce paraquat damage on peanuts, add a half pint of Basagran to reduce injury. If you have yellow nutsedge in a field or perhaps prickly sida, bump the Basagran up to a pint per acre or more to enhance control, he adds.
“In the pigweed world we’re living in today, there is a need to put out more residual herbicides at planting, incorporated or at early postemergence.
“If you do that, be aware you will almost always see more injury when Dual or Outlook is applied with paraquat even when Basagran is included.
“That’s not the end of the world — there will be more than normal injury symptoms, but yield will not be affected,” Jordan says.
Occasionally, when there are grass escapes, Basagran sometimes decreases the activity that paraquat would normally have on grass, he adds.
“In peanuts, if you have excessive damage from thrips, growers should not apply paraquat — significant yield reductions can occur in this case.”
With Temik not available for the 2012 growing season, the North Carolina specialist says researchers have ramped up tests with Orthene and other insecticides applied to emerged peanuts, to see how it fits in cases where in-furrow applications don’t work as well as desired.
In most cases tank mixes with Orthene and early postemergence herbicide applications have worked out fine — there doesn’t seem to be any significant damage or loss of efficacy with these tank mixes.
For grass control, Select and Poast and a number of generic versions of each have been around a long time and provide excellent grass control in a wide range of crops.
However, if these materials are tank-mixed with broadleaf herbicides, like Cobra, UltraBlazer, or Storm, you will get a 20-60 percent reduction in grass control.
Growers with major pigweed issues can use Dual and Outlook with grass herbicides and there seems to be no adverse compatibility issues with these materials, at least not in tests we’ve looked at so far, Jordan says.
In general, he adds, there have been few, if any problems when tank-mixing broadleaf herbicides like Cobra, Cadre, Pursuit or 2,4-DB, with an insecticide or fungicide.
Maybe an odd problem here or there, but in general we don’t see problems when tank-mixing broadleaf herbicides with other pesticides, he adds.
Later in the season — July and August — most peanut growers get grass escapes in peanuts. It makes sense to add grass herbicides with fungicides, because growers are typically applying fungicides every two weeks or so.
Jordan says chlorthalonil products or Headline or Abound tend to reduce grass control enough to get your attention.
“By contrast, we have not seen the same loss in grass herbicide efficacy when these materials are mixed with tebuconazole products and Provost,” Jordan says.
“Although it’s not on any label that I’m aware of, increasing the grass herbicide rate by 20-25 percent most likely will overcome the loss of grass activity in a tank-mix with fungicides,” Jordan points out.
“In general, we haven’t seen any major problems with disease control when fungicides are tank-mixed with herbicides or other pesticides. As long as these materials don’t settle out and cause problems in the spray tank, we just haven’t seen many problems,” Jordan says.
Likewise, there have been few problems with insecticide efficacy. Plant growth regulators, like Apogee, also have not had any significant problem with tank-mixing.
“And, some peanut growers are tank-mixing micronutrients, like boron and manganese, and only now and then do we see a minor drop in weed control, when these materials are tank-mixed with broadleaf herbicides,” Jordan says.
“We are sometimes concerned that applying boron with a herbicide and the appropriate adjuvant will produce more absorption and the possibility of foliar burn on peanuts.
“This does not seem to be a concern with manganese, but some foliar burn with excessive boron is not uncommon. The adjuvant often is the culprit in this case,” Jordan says.
There are thousands of options for tank-mixing and generally different pesticides are compatible with other materials with respect to foliar applications.
“There are also questions about mixing insecticides, fungicides and inoculant in the seed furrow. We do need to use caution here, Jordan stresses.
“With the price of seed, growers should be certain they will not do things like applying products in the furrow that have not been evaluated. There is too much at stake given the cost of peanut seed,” he adds.
(It has been said that it's all in the timing when talking about peanut disease and nematode control. And that would be especially true this year when acreage is expeced to increase by 25 percent. A University of Georgia specialist recently sat down to discuss that timing. To see his comments, visit http://southeastfarmpress.com/peanuts/peanut-disease-control-continues-be-focus-growers).
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