Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Master of Science in Entomology (MS)

Degree Level

Graduate

Department

Entomology and Plant Pathology

Advisor/Mentor

Thrash, Benjamin C.

Committee Member

Bateman, Nicholas R.

Second Committee Member

Lorenz, Gustav M. III

Third Committee Member

Robertson, Bill

Keywords

Tobacco thrips; ThryvOn cotton; Tarnished plant bug

Abstract

Tobacco thrips are an important pest in Mid-South cotton production. Thrips are a pest of seedling cotton, feeding on the leaf tissue of plants which can result in stunted growth, delayed fruiting, loss of apical dominance, and possible stand loss. Field studies were conducted in 2021 and 2022 to evaluate Thryvon, a new transgenic trait in cotton that produces the Bt toxin Cry51Aa, for control of tobacco thrips. Thryvon cotton was tested at three locations in Arkansas: Marianna, Tillar, and Keiser. These studies evaluated thrips control on ThryvOn vs non-ThryvOn cotton and the effect of insecticide seed treatments on ThryvOn cotton. Untreated ThryvOn cotton had fewer thrips and less injury than untreated non-ThryvOn cotton. ThryvOn cotton in combination with an insecticide seed treatment did not increase thrips control compared to untreated ThryvOn cotton. Controlled environment no choice tests were completed in 2021 to determine the feeding preference of adult tobacco thrips when presented a choice between ThryvOn and non-ThryvOn cotton seedlings. A higher number of thrips were observed on non-ThryvOn cotton seedlings. Results from these studies indicate that ThryvOn has the potential to be a valuable tool for thrips management. Tarnished plant bug (TPB) is the most economically important pest in mid-south cotton production causing square loss, deformed flowers, and damaged bolls, which ultimately reduces yield. TPB is difficult to control with growers averaging 4-6 insecticide applications per year. A field study was conducted at one location in 2021 and two locations in 2022 to evaluate ThryvOn for TPB control and the potential it has to change TPB management. These studies compared ThryvOn and non-ThryvOn cotton that was either untreated or sprayed at 1x, 2x, or 3x the current 3 TPB per 1.5 row m threshold. Based on our current 3 TPB per 1.5 row m threshold, ThryvOn required 2 applications for TPB compared to 5 in non-ThryvOn at Marianna. Untreated ThryvOn cotton had 14.8% higher square retention when compared to untreated non-ThryvOn. Yields in unsprayed ThryvOn were no different than any of the sprayed ThryvOn treatments. Behavioral response tests in the field for TPB were conducted with a cage study in 2022. Adult TPB were caged on the upper 4 nodes of non-ThryvOn and ThryvOn cotton. A greater TPB mortality and square retention was observed on ThryvOn cotton when compared to non-ThryvOn cotton. Results from these studies indicate that ThryvOn will be a valuable tool in TPB management.

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