Whereas many cotton growers are eagerly awaiting the full industrial launch of ThryvOn Expertise to assist handle thrips and tarnished plant bug infestations, there’s nonetheless the matter of this crop season. What are the very best methods for managing these pests earlier than the “easy button” arrives available on the market?
Scott Stewart, professor of entomology and director of the West Tennessee AgResearch and Schooling Heart supplied an insect management update for 2021 in the course of the College of Tennessee Institute of Agriculture’s digital Cotton Focus. He mentioned the foremost pests of the northern cotton belt and simplest management strategies in line with his analysis.
Tobacco thrips could be a substantial pest of cotton if they’re not managed. Happily, in line with Stewart, relating to thrips administration, growers should be good however not good to protect yields. In a seven-year analysis trial, managing for thrips with only a neonicotinoid insecticide seed therapy averaged a 107 lb/a lint improve over non-treated plots. That comes out to a internet worth of roughly $70 per acre.
“We know there’s a significant economic advantage on average to managing thrips in cotton,” Stewart mentioned. “You don’t always realize this return — sometimes you see no benefit — but other times it’s substantially more.”
There are a selection of seed and in-furrow remedies that may cut back thrips damage, though in line with Stewart’s analysis, they fluctuate of their efficacy. He recommends beginning with an imidacloprid base seed therapy. For growers contemplating an add-on therapy, Stewart says Aeris has supplied some further safety above imidacloprid alone in latest trials. AgLogic, an aldicarb pesticide utilized in-furrow, has additionally proven to offer good thrips management.
Whereas acephate seed or in-furrow remedies are well-liked in some geographies, they haven’t risen to the highest in latest analysis trials in western Tennessee.
“Acephate as a seed treatment or even by itself as an in-furrow treatment is not providing particularly good control,” Stewart mentioned. “It provides some protection, but we have pretty good information that our tobacco thrips are developing resistance to some of these insecticides, particularly acephate.”
Given the issues over thrips resistance, foliar-applied pesticides will fairly often be needed, significantly in robust climate circumstances or areas with excessive thrips stress.
“Usually, we recommend one insecticide application very early,” Stewart mentioned. “At about first leaf stage is the best timing.”
In 2020 trials, Intrepid Edge and Radiant, which each include the lively ingredient spinetoram, had been the highest foliar insecticide remedies for thrips in Stewart’s trials. Each come at a premium worth in comparison with Orthene, however in recent times, these merchandise have outpaced Orthene in thrips management, which Stewart attributes to creating acephate resistance.
“Presuming you have an imidacloprid seed treatment, I think we can continue to use Orthene,” Stewart mentioned, “but I do suggest you use a higher rate of acephate. That does seem to overcome some of the issues to resistance we’re seeing. Bidrin is an option that can also be considered.”
Stewart can also be main research trying on the impression of plant density and insecticide seed therapy together on thrips damage.
“In my experience, when we have thinner plant stands we see higher thrips injury. We’re not really sure why that’s happening, but our data is confirming that,” Stewart mentioned.
Rising analysis is exhibiting will increase in thrips damage as plant populations are reducing. Remoted crops are inclined to have worse thrips damage, even when a seed therapy was utilized. Stewart recommends not reducing seeding charges too low to keep away from potential for thrips points.
“If you have a poor stand to begin with and then have high thrips pressure, it’s going to make it necessary to make that foliar application and maybe two to control thrips,” Stewart mentioned.
Curious as to what degree of thrips stress you may anticipate for 2021? As your planting date approaches, Stewart suggests visiting the web Thrips Infestation Predictor for Cotton. This device, developed by college at North Carolina State College, gives predictions for thrips dispersal and damage threat based mostly on planting date and climate circumstances in your location.
The knowledge can be utilized to optimize collection of thrips administration measures and prioritize scouting.
Within the second a part of his presentation, Stewart transitioned to plant bugs, starting with figuring out thresholds for therapy. For tarnished plant bugs the primary two weeks of squaring are crucial, and growers ought to deal with upon discovering eight or extra plant bugs per 100 sweeps. After the third week of squaring, the therapy threshold is relaxed to fifteen plant bugs per 100 sweeps, however Stewart cautions that anytime sq. retention drops under 80 p.c and plant bugs are current, therapy must be thought-about.
“In my tests and trials across the Mid-South, Diamond, Orthene and Transform are consistently the top three insecticides for managing tarnished plant bug numbers,” Stewart mentioned.
Stewart mentioned a season-long strategy to managing plant bugs, in addition to stink bugs created substantial yield will increase in his trials — on common a 1,250-pound improve in seed cotton in comparison with doing nothing.
“You may’t overlook to account for stink bugs or different pests. I’m a giant fan of utilizing mixes or rotating these top-shelf insecticide merchandise. I like mixes of merchandise like Orthene, Diamond, Rework, and Bidrin.
“We’re seeing some neonicotinoid resistance. I think neonicotinoids still have a place, but it’s in the early squaring window. They don’t have a place after flowering at all.”
Stewart additionally mentioned non-insecticide approaches to plant bug administration.
“When we have cotton near corn, there tend to be more plant bugs in the area, so you can try to avoid that affect by blocking cotton together,” Stewart mentioned.
“Planting early as early as practical is always recommended. For Tennessee, I think it’s very important to use early or mid-maturing varieties. You’re very likely to have to make an additional insecticide application if you’re growing more full season varieties.”
As a result of it’s within the stewarded launch section, cotton with ThryvOn Expertise will solely be obtainable on a restricted foundation to pick out growers in the course of the 2021 crop season. Stewart has evaluated the trait since 2014 and feels assured that upon it’s full-scale launch, ThryvOn can be a helpful device for growers.
“It’s excellent at reducing thrips injury. In our ThryvOn evaluations, we never rated thrips injury greater than 1.0 on a 0 – 5 scale. That’s essentially unheard of with an insecticide seed treatment or in-furrow treatment for thrips.”
This know-how is delaying and lowering the buildup of tarnished plant bugs. Due to that, we’re not having to make as many insecticide functions,” Stewart mentioned.
In College of Tennessee trials, ThryvOn Expertise decreased the necessity for foliar insecticide functions for thrips and plant bugs by half. For ThryvOn, two functions for tarnished plant bugs and stink bugs had been required, whereas spray thresholds for thrips had been by no means triggered. Evaluate that to non-traited varieties, which required on common one foliar software for thrips and three functions for tarnished plant bugs for a complete of 4 functions.
“We are going to have to continue to manage plant bugs even after ThryvOn,” Stewart mentioned, “but we may realize insecticide savings.”
UT Cotton Focus
The Cotton Focus displays are being launched weekly on the UT Crops New Blog. As of press time, webinars on weed management, illness administration and the Cotton Belief Protocol had been additionally obtainable.