Missouri Ruralist logo

Treatment tips for thrips

How to know whether your pest control management practices failed on cotton acres.

Mindy Ward, Editor, Missouri Ruralist

June 6, 2024

4 Min Read
thrips damage on a cotton plant
PLANT DAMAGE: There are five distinct thrips damage ratings for cotton plants. Zero is no injury, while 5 equals dead plants. This picture represents a 2. John C. French Sr., Retired, Universities:Auburn, GA, Clemson and U of MO, Bugwood.org

Missouri’s cotton farmers are trying to outrun thrips injury, but the weather is not cooperating.

“Sadly, 2024 has not been an ideal year for thrips management due to the consistent overcast during the daytime hours,” reports Chase Floyd, University of Missouri Extension state crop protection specialist based in the Bootheel. “This restricts thrips movement and can increase injury.”

Reaching the fourth true leaf stage is crucial for cotton plants to outpace thrips damage. However, with limited hot and sunny days to speed up growth development, farmers need management options.

Floyd offers some advice on how to control thrips:

In-furrow boost. Liquid in-furrow applications of imidacloprid have shown better success compared to seed treatments. However, thrips resistance to neonicotinoids (including imidacloprid) is reducing efficacy. “It is likely that in-furrow imidacloprid applications will require a foliar spray in the Bootheel,” Floyd notes.

Foliar and mites. There are limited foliar options that are efficacious for thrips control in cotton. MU Extension conducted bioassays near Holcomb in 2023 to monitor thrips resistance to organophosphates (OPs). Results showed that commonly applied OPs, such as Acephate and Bidrin, reduced thrips populations by 37% and 80%, respectively.

The Bootheel region faces a challenge with OP applications because of the risk of spider mite outbreaks. The sandy soil profile allows precipitation to drain quickly, creating a dry environment conducive to spider mites.

When considering OPs, check the forecast for higher humidity post-application. Humidity can suppress thrips but may also increase spider mite risk.

“If forecasts predict hot and dry weather conditions in the near future, I typically will avoid applying OPs if possible,” Floyd adds.

Insecticide cost. Intrepid Edge is a more expensive option compared to OPs, but it offers benefits like no risk of spider mite or aphid outbreaks. Bioassays also demonstrated 100% control regardless of location in the cotton belt.

For better efficacy, add surfactant and oil (if tank-mixing). Consider using finer droplet nozzles to increase droplet density. Apply 3 fluid ounces per acre of Intrepid Edge regardless of tank-mix.

Floyd says Intrepid Edge provides three to four days of protection, which is longer than the initial knockdown achieved with OPs.

If you have any questions concerning thrips management decisions, call Floyd at 901-493-2377.

What control failure looks like

Understanding the distinction between recolonization and failure in managing thrips is crucial for effective control.

Here’s the breakdown:

Recolonization

Scenario: After a foliar application, you observe adult thrips still present on the cotton plants.

Explanation: This does not necessarily mean the product failed. Adult thrips are constantly dispersed by wind, and their presence is expected even after treatment.

Takeaway: Don’t panic if you see adult thrips; they’re part of the natural population dynamics.

Treatment failure

Scenario: You notice immature thrips (juveniles) following the application.

Explanation: Immature thrips indicate active feeding and egg-laying. If they persist after treatment, it means the foliar application is no longer effective.

Action: Consider alternative strategies or reapplication to address the ongoing thrips pressure.

Plan for thrips in 2025

Floyd offers a few management options for thrips control to consider in 2025, particularly in Bootheel cotton acreage.

Variety selection. ThryvOn is Bayer’s Bt technology designed to target thrips and plant bugs. ThryvOn varieties are highly effective against thrips, Floyd says, and foliar applications for thrips are unlikely to be necessary.

When scouting these varieties, be aware that both adult and immature thrips will be present. However, insecticide applications should not be based solely on thrips numbers. Instead, consider the level of damage.

“With that said, my colleagues and I across that cotton belt have looked at ThryvOn varieties for several years, and no one has yet to recommend a foliar application to any ThryvOn,” Floyd notes.

Seed treatment. Insecticide seed treatments are the primary method for thrips control in cotton. Their effectiveness varies based on weather conditions and thrips pressure.

In the Bootheel region, where wheat is used as a cover crop, thrips pressure tends to be higher, Floyd says. As wheat dries down after planting, thrips move directly to the emerging cotton.

Seed treatment packages typically include a base (with imidacloprid + fungicide) and field rates (with higher imidacloprid + fungicides). The base rate offers minimal control, so a minimum imidacloprid rate of 0.375 mg ai per seed is needed for effective field control.

Remember to adapt these strategies based on local conditions and consult with local experts for the most effective thrips management in your specific area.

About the Author(s)

Mindy Ward

Editor, Missouri Ruralist

Mindy resides on a small farm just outside of Holstein, Mo, about 80 miles southwest of St. Louis.

After graduating from the University of Missouri-Columbia with a bachelor’s degree in agricultural journalism, she worked briefly at a public relations firm in Kansas City. Her husband’s career led the couple north to Minnesota.

There, she reported on large-scale production of corn, soybeans, sugar beets, and dairy, as well as, biofuels for The Land. After 10 years, the couple returned to Missouri and she began covering agriculture in the Show-Me State.

“In all my 15 years of writing about agriculture, I have found some of the most progressive thinkers are farmers,” she says. “They are constantly searching for ways to do more with less, improve their land and leave their legacy to the next generation.”

Mindy and her husband, Stacy, together with their daughters, Elisa and Cassidy, operate Showtime Farms in southern Warren County. The family spends a great deal of time caring for and showing Dorset, Oxford and crossbred sheep.

Subscribe to receive top agriculture news
Be informed daily with these free e-newsletters

You May Also Like