I’ve received a few calls on adult tarnished plant bug migration into squaring cotton. Silking corn, blooming soybeans and flowering pigweed all contribute to large increases in plant bug numbers that make their way to ThryvOn and non-ThryvOn cotton.  ThryvOn’s bt gene can help reduce the amount of injury plant bugs inflict to squaring cotton but adults, especially large numbers of adults, can knock squares off of ThryvOn just like non-ThryvOn. I’ve seen ThryvOn cotton go from 90 plus percent square retention to sub 50 percent in 5 days due a large, consistent migration of adult plant bugs. The biggest benefit we see from ThryvOn is the reduction of plant bug immatures in bloom. That being said, you will typically see increased square retention in ThryvOn vs non-ThryvOn throughout the fruiting period. Scout your cotton and don’t ignore migrating plant bugs in ThryvOn or non-ThryvOn.  Also, many of the newer varieties begin squaring on the 5^th or 6^th node and we need to quickly transition from scouting for thrips to plant bugs.

Based on field reports, 2.0 oz/a of Centric is performing well on plant bug populations. Although the same class of chemistry, imidacloprid’s performance is fair at best and recolonization often happens quickly after an imidacloprid application. I try to not recommend consecutive applications of neonics due to efficacy falling off after the first shot. However, consecutive shots of neonics may be warranted for several reasons (cost, presence of mites, personal choice etc.) and on the second application I tend to increase rates of Centric to 2.5 oz/a especially if it was used previously. After the second application we’ve pretty much exhausted that chemistry. Other options are: acephate which carries a high risk of flaring mites and aphids especially in our current dry period, Vydate which is effective in killing plant bugs but has limited residual, roughly 36 hours, Bidrin isn’t labelled for plant bugs between first square and bloom, Transform, which is very effective, but is expensive and many want to save those shots for bloom unless aphids are present and Diamond. Diamond’s activity is best utilized in the 3^rd week of squaring to first bloom window, several studies at MSU and UT have shown the best ROI of 6.0 fl oz/a Diamond during that time period.

Final note, I’ve received a few questions on squaring cotton having poor square retention but very few or no plant bugs are found scouting. Adult plant bugs, especially at this time of year, will move in and out of cotton quickly. The abundance of alternative hosts facilitates movement in and out of cotton without colonization. The take home is since most are scouting once a week, it is prudent to be more aggressive with applications and not risk square retention falling below 80% if you’re close. Monitoring square retention is one of, if not, the best way to determine if early-season treatments are working. Migrating adults can give the impression of an insecticide failure, but maintaining good square retention is a good indication that treatments are working.

With warm conditions moving into West TN, many producers are  underway with cotton planting. Below are a few things to consider with regards to thrips control.

ThryvOn: ThryvOn is Bayer’s Bt technology that has activity on thrips and plant bugs. ThryvOn cotton varieties are very effective against thrips and it is not anticipated that any fields will need foliar  treatments. ThryvOn will still have thrips present (adults and immatures) but insecticide applications should not be triggered on thrips numbers but damage level (Fig 1.). Applications should be initiated when plant damage is approaching 3 in figure 1. That being said, I’ve evaluated ThryvOn varieties for several years under excellent and terrible growing conditions and I as well as my colleagues across the cotton belt, have never recommended a foliar spray for thrips.

Insecticide Seed Treatments (ISTs): ISTs are the predominate control method for thrips in cotton. IST performance can be highly variable depending on weather conditions and thrips pressure. High thrips pressure and poor growing conditions will often necessitate the use of foliar sprays even with ISTs. Seed treatment packages typically come in a base (storage rate of imidacloprid + fungicide) and field rates of imidacloprid (these have several names) + fungicides, others may have nematicides, biologicals etc. Base treated seed may as well have no insecticide, the small stored product rate will offer almost no control of insects in the field. Standard options of imidacloprid (0.375 mg ai/seed) are the minimum needed for insect control in field cotton.

In-furrow: In-furrow liquid applications of imidacloprid are more effective than seed treatments; however, resistance development to neonicotinoids are diminishing the efficacy of imidacloprid in-furrow. Fields with in-furrow imidacloprid may still require a foliar spray under heavy thrips pressure. Granular AgLogic (aldicarb 15G) is highly effective against thrips populations and works like aldicarb should.

Foliar Spray Options: My recommendations are going to be limited for foliar sprays. Based on ongoing tobacco thrips resistance monitoring, to organophosphates (OPs), started by Scott Stewart several years ago, I am hesitant to recommend Orthene or Bidrin for thrips sprays. Resistance levels, in assayed populations from West TN, and the number of complaint calls I received last year are a good indication that OPs have limited use against our tobacco thrips populations. There may be areas where OP’s worked last year but it’s hard to say if they will work this year. That being said, Intrepid Edge at 3.0 fl oz/a is my go to for foliar thrips control. Although more expensive than the OPs, Intrepid Edge runs no risk of flaring mites or aphids and a surfactant has shown to increase efficacy (herbicide surfactants will work if you’re co-applying). Recolonization vs failure is another subject with foliar sprays. Presence of adults doesn’t mean the application didn’t work, adult thrips are always present on seedling cotton. Presence of immature thrips means adults are feeding and laying eggs and whatever control method you used is broken.

I am big believer in NCSU’s thrips predictor model https://products.climate.ncsu.edu/ag/cottontip/. We utilize the model to target planting when thrips numbers are highest, growers would do the opposite. Model runs for locations around West TN show that cotton planted May 1^st through the 15^th have a low to medium probability of experiencing large thrips populations. This is hopefully a welcome relief from years of cold, wet springs with large thrips populations plaguing our cotton. The warm weather will help germinate cotton quicker and standard ISTs may be enough to push us to the 4 true leaf stage (when thrips are typically no longer a concern) without a foliar spray.