Degree

Doctor of Philosophy (PhD)

Department

Entomology

Document Type

Dissertation

Abstract

Furrow-irrigated rice (FIR) (Oryza sativa L.) is an upland irrigation system that has expanded rapidly across the U.S. Midsouth over the past decade. In FIR, rice is planted on shallow raised beds and water is delivered through furrows via polypipe. Key advantages include improved water-use efficiency, reduced labor, and compatibility with rotations involving corn, cotton, and soybean. Despite these differences from traditional flooded systems, insect management in FIR largely mirrors flooded rice practices, particularly the widespread use of insecticidal seed treatments (ISTs) targeting rice water weevil (Lissorhoptrus oryzophilus Kurchel). However, irrigation differences may alter pest communities, reducing pressure from semi-aquatic pests and elevating the importance of upland pests such as the rice billbug (Sphenophorus pertinax Olivier), which was historically minor. This dissertation aimed to improve understanding of insect pests associated with FIR and refine management approaches to align with integrated pest management principles. From 2022–2024, field surveys of commercial fFIR operations characterized pest and natural enemy communities. Wasps and spiders were the predominant natural enemies. Surveys also revealed that S. pertinax infests nearly all FIR hectares in Louisiana, with greater infestation linked to corn–rice rotations and tail-water release irrigation. A three-year multi-state small-plot experiment evaluated ISTs (thiamethoxam, clothianidin, cyantraniliprole, and chlorantraniliprole) across two irrigation tactics (tail-water release vs. end-blocked). ISTs did not reduce S. pertinax densities or injury. Yield benefits were inconsistent and largely confined to areas with high pest pressure. Tail-water release consistently increased both injury risk and yield loss. A separate two-year experiment conducted with multiple universities assessed cultivar resistance/tolerance and quantified yield loss associated with S. pertinax injury. Some commercial cultivars exhibited resistance and estimated yield loss ranged from 0.5–2% per whitehead per m². Finally, analysis of ≈600 panicles from FIR fields showed that injured panicles still filled ~47% of kernels compared to ~76% in uninjured plants, and that grain loss increased with later planting dates. Collectively, this work provides a foundation for sustainable insect management in FIR and clarifies the economic impact of S. pertinax as the principal weevil pest in the US Midsouth.

Date

11-20-2025

Committee Chair

Blake Wilson

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Available for download on Friday, November 20, 2026

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