Use caution when reducing peanut herbicide rates

As we head into the time when postemergence herbicides are applied in peanuts, growers have asked many questions about the use of reduced rates of Cadre. Producers are interested in using lower rates of Cadre to minimize production costs and lessen the potential of having cotton carryover problems.

This issue has been discussed at many county production meetings and individual farm visits, but I would like to set the record straight on my opinion about reduced rates of Cadre.

Labeled rate

Before anything else, remember that the labeled rate of Cadre 70DG is 1.44 ounces per acre. This rate is designed to provide the most consistent weed control performance over a wide range of application conditions. Very rarely will Cadre fail when it is applied at this rate.

Next, understand that it is not illegal to use a reduced rate of Cadre or any other herbicide. However, BASF is not liable for poor performance of Cadre applied at low rates. The grower bears the burden if it does not perform satisfactorily.

No guarantee

Lastly, the use of lower rates of Cadre is no guarantee for preventing carryover to cotton. Herbicide degradation is influenced by factors other than rate including moisture, temperature and soil pH. The only sure way to avoid cotton problems with Cadre is not to use it on your peanuts!

With that said, what do we know about the use of lower rates of Cadre?

Several research trials have been conducted across the Peanut Belt to address this issue. Generally, results have indicated that Cadre applied at low rates can provide adequate and effective weed control for selected weeds in certain situations. However, in order for these reduced rates to work, many conditions must be met.

The first of these is related to weed susceptibility. All weeds are not created equal. Some are more sensitive to Cadre than others. For example, yellow and purple nutsedge are very sensitive to Cadre, while weeds like beggarweed and sicklepod are not. Consequently, reduced rates of Cadre for control of beggarweed and sicklepod are unwise.

Second condition

The second condition critical to the performance of reduced rates is application timing. Reduced rates must be applied when the weeds are SMALL

A ‘small’ weed is one that is two inches or less in height. Reduced rates applied after this stage of growth are doomed for failure.

The third factor critical to the success of reduced rates is the environmental conditions at the time of application. Ideal conditions for the use of low rates include ample soil moisture levels, warm but not extreme temperatures, and high humidity. As you already know from previous experience, weeds growing under drought stress are hard to kill even with a full rate.

Another issue of concern regarding the use of reduced rates is the potential to increase the development of herbicide-resistant weeds.

Although opinions vary, many weed scientists believe that the development of herbicide resistance is a function of selection pressure and not the herbicide use rate. If a reduced rate of Cadre provides acceptable weed control, there is no reason to believe that weed resistance is more likely to increase than when full rates are used.

On the flip side, repeated use of a low rate that results in marginal weed control could increase the risk of developing weed resistance.

Situations differ

Although reduced rates of Cadre can be very effective, they are not for every grower and every weed control situation. If you have had consistent success with full rates of Cadre and now want to experiment with reduced rates, you must consider weed susceptibility, application timing and the environment.

You must also be willing to accept the risk of failure if these conditions are not ideal.

On the other hand, if you have been unable to achieve satisfactory weed control with a full rate of Cadre, don't even consider applying a below-labeled rate.

As always, good weed hunting!

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