I’ve received several phone calls about spider mites increasing in cotton around West Tennessee. Spider mites favor hot, dry weather and will often become an issue after plant bug applications are initiated. UT recommends treatment when 30-50% of plants are showing signs of injury and spider mites are still present.  This may be too aggressive under low stress conditions, but most of the crop is currently under substantial heat and drought stress. Treatment options are fairly limited and most are mite specific. Abamectin based products are typically the first option because they are economical and effective. There are a couple different formulations of abamectin that are different lb/ai per gallon products.  Below is a rate conversion of 0.15 lb ai/gallon formulations (Willowood Abamectin 0.15 EC, etc)  to 0.7 lb ai/gallon formulations (Agri-mek SC 0.7, Willowood 0.7 SC, etc).

5.0 fl oz/a = 1.0 fl oz/a

7.0 fl oz/a = 1.5 fl oz/a 

8.0 fl oz/a =1.75 fl oz/a

10.0 fl oz/a = 2.0 fl oz/a

Abamectin rates below 7.0 fl oz/a or 1.5 fl oz/a should be avoided due to potential resistance issues and the increased likely hood of retreatment.

Other mite products such as etoxazole (Zeal, Stifle) are mite growth regulators that work very well but are more expensive and somewhat slower than traditional miticides.  Fenpyroximate (Portal) is a contact miticide that has a shorter residual than abamectin or etoxazole but  works very well. Bifenthrin alone is not an adequate miticide and should be avoided.

Products used for controlling plant bugs, bollworms and stink bugs (OPs, pyrethroids) exacerbate mite populations and their use, especially during hot dry conditions, should be delayed until after bloom if possible. Mite populations can rebound quickly after miticide applications so diligent scouting is critical to slowing the spread of mites across a field.

I’ve received several phone calls over the past few days about thrips in seedling cotton. Thrips pressure is variable by location with some areas reporting treatable numbers and others finding a few adults scattered around.  Application timing is critical for the best control.  Our research has shown that applications made early, before the second true leaf, provides the most benefit.

Options for foliar oversprays are limited to organophosphates  (Acephate, Bidrin, Dimethoate) and Intrepid Edge. OP resistance is present in West TN and while Acephate may provide some relief a more consistent option is 3.0 oz of Intrepid Edge. Also, increasing the rates of OPs may help some but overcoming resistance with higher rates often doesn’t provide consistent control and can be an expensive mistake.

The take home message, use acephate or other OPs with caution especially if you received questionable control last year and higher rates often aren’t the answer. Intrepid Edge, although the most expensive, is most consistent option that won’t flare spider mites or aphids. Surfactants aren’t required for Intrepid Edge but are highly recommended. Application with a herbicide such as Roundup or Liberty will work.

Side note: I’ve got word that Bidrin is in short supply so if you don’t have what you need for thrips I would think about making other arrangements.

The thrips infestation predictor tool uses planting date, precipitation, and temperature to create an estimate of the size of local thrips population and the susceptibility of seedling cotton to infestations of tobacco thrips (the predominate thrips species in Tennessee). Models can be run for two weeks  beyond the current date. Planting decisions should be made based on weather, opportunity and agronomic considerations not based on this model.  The model is useful for predicting/anticipating the need for a thrips overspray in addition to an insecticide seed treatment.

Utilizing the model is simple,  users select a planting date and a location based on an interactive map. The model will predict thrips risk for planting dates in a designated time frame. As an example, cotton planted before May 5th in West Tennessee has a somewhat lower risk than cotton planted on May 15th.  If you look at the within season model, cotton planted May 21- 31 has a much higher risk of thrips infestations than cotton planted in early May.  Beware,  the accuracy of this model often improves as we approach the intended planting date and rerunning the model as you get closer to planting is a good practice.  This tool has helped us time our planting of thrips trials to maximize thrips numbers and will hopefully help you do the opposite.

A reminder the Thrips Infestation Predictor for Cotton described in the article below, published last year, is still available for use.  However, the link has changed to  https://products.climate.ncsu.edu/ag/cottontip/.

———————————————————————-

The Thrips Infestation Predictor for Cotton is a useful tool for predicting whether a foliar insecticide application is needed for thrips control in cotton. It uses local weather data in association with a user defined planting date to estimate the size of the local thrips population, the susceptibility of seedling plants, and thus, the risk of thrips injury. The model is for tobacco thrips, by far the most common species infesting cotton in Tennessee. Continue reading →