Degree

Doctor of Philosophy (PhD)

Department

Entomology

Document Type

Dissertation

Abstract

Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most destructive insect pest of rice in the United States. Lissorhoptrus oryzophilus larvae feed on rice roots, reducing yields by up to 25 %. Lepidopteran stem borers, in the family Crambidae, are also economically important pests of rice in Louisiana.

Currently, insecticidal seed treatments are used throughout the U.S. Mid-south rice industry to prophylactically control L. oryzophilus. Chlorantraniliprole seed treatments are also effective against stem borers. Thus, insecticidal seed treatments are used on >80 % of Louisiana rice acreage. Although seed treatments reduce damage inflicted by these pests, they are applied preventatively and do not adhere to the fundamentals of integrated pest management (IPM). Additionally, over reliance on a single insecticide promotes pesticide resistance through increased selective pressure. This dissertation aimed to improve the efficacy and sustainability of insecticidal seed treatments in accordance with IPM principles.

Two years of data were collected in Acadia, Jefferson Davis and Vermillion Parishes to understand the spatial distribution of L. oryzophilus and stem borers in Louisiana rice. Pest populations had an edge-biased distribution. Lissorhoptrus oryzophilus was also influenced by distance from overwintering/alternative non-crop habitat, while stem borer populations were influenced by region.

A three-year small-plot experiment investigated the integration of chemical and cultural control practices in rice. Results demonstrated that early-planting and delayed-flooding work synergistically to reduce L. oryzophilus and stem borer pest incidence and injury. Chlorantraniliprole was the most effective tool for managing both pests. However, the neonicotinoid, thiamethoxam, can be used in conjunction with cultural controls as an alternative to chlorantraniliprole, especially in areas with low stem borer populations.

Remote sensing, using unmanned aerial vehicles equipped with multi-spectral cameras, produced vegetation indices that were significantly correlated with L. oryzophilus densities. Four indices can be used to predict yields and L. oryzophilus induced crop stress. This could enhance monitoring of L. oryzophilus on large commercial farms.

This research can be used to improve deployment of seed treatments and IPM implementation in Louisiana rice. It elucidates potential tools for moderating the risk of pesticide resistance, supports decision making processes and explores avenues for reducing input costs.

Date

11-14-2021

Committee Chair

Wilson, Blake E.

Included in

Entomology Commons

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