Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Master of Science in Entomology (MS)

Degree Level

Graduate

Department

Entomology

Advisor/Mentor

Nicholas Bateman

Committee Member

Benjamin C Thrash

Second Committee Member

Gustav M Lorenz III

Third Committee Member

Jarrod T Hardke

Fourth Committee Member

Neelendra Joshi

Abstract

Rice stink bug, (RSB), Oebalus pugnax (F.), (Fabricius 1775) is the major pest of headed rice, Oryza sativa L. in the southern rice producing states. The evaluation of current insecticides is imperative to efficient and economical RSB management for rice growers. Multiple reports of field failures with lambda-cyhalothrin have been documented since 2019. Lambda-cyhalothrin has been the standard for RSB control for the past two decades. The objective for this research was to determine if RSB is becoming resistant to lambda-cyhalothrin in Arkansas, and the most economical insecticide choice for growers with respect to RSB control and grain quality. RSB populations were collected throughout Arkansas throughout the growing season to determine resistance levels to lambda-cyhalothrin. Increased resistance to lambda-cyhalothrin in RSB populations in Arkansas is occurring, among naturally diverse RSB populations. Lower mortality was observed for collections made in August compared to May, June, or July. Based on results from this study growers and consultants should not anticipate more than 70% control with lambda-cyhalothrin, and commonly a decrease in percent control as the growing season progresses. These assays were direct exposure, and less control should be anticipated in a field setting. Foliar insecticide comparison trials were conducted in 2021 and 2022 at a total of 7 sites, to evaluate insecticides for efficacy and residual control of RSB, and to determine any subsequent on rice quality. Lambda-cyhalothrin provided lower control of RSB nymphs at all sampling dates, up to 14 DAT, compared to dinotefuran and thiamethoxam + lambda-cyhalothrin. Dinotefuran and thiamethoxam + lambda-cyhalothrin had less RSB damage (“peck”) compared to all other treatments excluding carbaryl. Total peck was reduced with dinotefuran and both rates of thiamethoxam + lambda-cyhalothrin across all locations, compared to malathion, zeta-cypermethrin, and lambda-cyhalothrin. Return on investment was the highest in dinotefuran, thiamethoxam + lambda-cyhalothrin, and carbaryl treated plots compared to lambda-cyhalothrin. Foliar timing experiments were performed in 2022 over three field sites, to establish at which time in grain maturity is treatment for RSB is most crucial to preserve grain quality. This study observed common trends between the three test locations, where RSB peck was higher in lambda-cyhalothrin treated plots compared to dinotefuran and thiamethoxam + lambda-cyhalothrin. Applications of lambda-cyhalothrin only lowered RSB peck when applied late or applied twice compared to the untreated check (UTC). No differences were observed between thiamethoxam + lambda-cyhalothrin and dinotefuran within or across application timing. Greater net returns were observed for thiamethoxam + lambda-cyhalothrin and dinotefuran, at each treatment timing compared to lambda-cyhalothrin and the UTC. A trend was observed that an application of either dinotefuran or thiamethoxam + lambda-cyhalothrin at the soft dough growth stage provided greater returns on investment than an application made during flowering or at both timings.

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