Date of Graduation

12-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Entomology (PhD)

Degree Level

Graduate

Department

Entomology

Advisor

Gus M. Lorenz

Committee Member

Jarrod T. Hardke

Second Committee Member

Donn T. Johnson

Third Committee Member

Nicholas R. Bateman

Fourth Committee Member

Glenn E. Studebaker

Fifth Committee Member

Jeffrey Gore

Keywords

Economic Threshold, Grain Sorghum, Milo, Rice, Rice Stink Bug, Sampling

Abstract

Rice stink bug, Oebalus pugnax (F.), is a serious pest of headed rice, Oryza sativa L. and an occasional pest of heading grain sorghum in the Mid-south. Work from this dissertation focuses on resolving gaps in and knowledge of rice stink bug sampling and management, and attempts to create a basis for rice stink bug damage assessment in future studies.

Field experiments were conducted from 2016-2018 to asses variation in sweep net sampling by observing producers, researchers, extension personnel, consultants and their workers. Large levels of variation were found in sweep lengths between observed sweepers and reliability of smaller sweep lengths that were commonly used was evaluated. Controlled sweep lengths of 0.9m, 1.8m, and 3.5m were evaluated and significant differences in rice stink bug collection were observed. Sweep net samples measuring 1.8m or greater per sweep were determined to be accurate and reliable, and therefore are recommended for future sampling.

In 2018, uncaged trials were conducted to relate sweep net samples of 1.8m to direct and indirect yield loss by the rice stink bug. Peck levels and total milled rice were affected by rice stink bug density, whereas data on total head rice and direct yield loss were less clear. These results confirm the validity of the current Arkansas indirect yield loss threshold of 10 rice stink bugs during the second two weeks of heading.

In 2016-2018, insecticide termination timing for rice stink bug in rice was determined based on visual evaluation of percent rice grain maturity (hard dough). Data suggested that rice with low percentages of hard dough kernels were susceptible to indirect yield loss, but applications can be terminated at 60% hard dough if threshold-level populations aren’t present.

Experiments were performed in 2016 and 2017 to determine the amount of yield loss caused to grain sorghum by rice stink bug feeding at different heading growth stages, and to develop dynamic thresholds for these stages. These data indicate that rice stink bug poses its greatest threat to grain sorghum in the early heading growth stages, and yield loss potential decreases as grain sorghum matures.

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