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Insecticide resistance financial liability in increased input costs, yield losses

From the infamous boll weevil to the stubborn tobacco budworm, cotton growers face a variety of insect problems year after year.

To keep these damaging pests in check and maintain genetic yield potential, they rely on the effectiveness of insecticides. While insecticide resistance problems first became widespread in the mid-1950s, these issues aren't new to growers, but preserving existing insecticide technologies has become a real priority.

Most growers today realize the resistance problem is real. “Cotton growers in the Mid-South are very aware of insecticide resistance,” said Randy Luttrell, University of Arkansas entomologist. “They know they might only have one or two shots with some insecticides like pyrethroids.”

In response, many producers are incorporating better methods to preserve valuable control options. They are waiting for economic thresholds before spraying, and making efforts to protect beneficials by using narrow-spectrum insecticides more frequently. Growers also are taking advantage of newer chemistries such as neonicotinoids.

Neonicotinoids are a relatively new class of insecticides that have become a common replacement option for organophosphates and pyrethroids. “Neonicotinoids are excellent replacement products that give us a chance to alternate our chemistries,” said University of Tennessee entomologist Scott Stewart.

Neonicotinoids are more selective insecticides that control insects by binding and inhibiting specific neuroreceptors. In addition, there is no evidence for target-site resistance within this class. Target-site resistance is important because it is a precursor to cross-resistance, which can render chemistries that share a similar mode of action (MOA) ineffective.

Neonicotinoids have been classified Group 4A by the Insecticide Action Resistance Committee (IRAC). (For more information on insect resistance management, go to IRAC on the web at

Thiamethoxam is a member of this group and was the first available second-generation neonicotinoid. Thiamethoxam is the active ingredient in both Cruiser seed treatment insecticide and Centric insecticide, which have proven to be effective applications to control a variety of cotton pests.

While Cruiser targets thrips, Stewart believes Centric has become a primary early-season product used to control plant bugs and aphids.

For growers, insecticide resistance can be a tremendous financial liability in both increased input costs and yield losses sustained from pest damage. Luckily, there are a variety of ways to help prevent this problem.

One of the most valuable and widely used methods is alternating chemistries that have a different MOA, especially when multiple applications are needed in the same field. Incorporating this technique is one of the best ways to reduce selection pressure.

Success against insects often depends on timing applications when pests are most vulnerable. Using this method can maximize the effectiveness of insecticides and reduce the need for further applications. Be sure to consider factors such as pest levels, plant development and weather conditions to target pests in this manner.

When spraying insecticides, remember to use the effective labeled rate with equipment calibrated to provide thorough and uniform coverage. Clogged spray nozzles, inefficient pumps and inaccurate speedometers can all contribute to improper coverage.

Integrated pest management programs are the best way to approach insect control and manage resistance.

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