Semester of Graduation

Spring 2026

Degree

Master of Science (MS)

Department

Entomology

Document Type

Thesis

Abstract

Clean-seed programs in vegetatively propagated crops rely on pathogen-tested planting material, yet maintaining low virus incidence during field multiplication remains challenging because dispersing alate aphids can introduce and spread nonpersistently transmitted potyviruses. This thesis aimed to characterize seasonal patterns of aphid immigration to identify periods of elevated transmission risk and when supplemental management tactics should be deployed, as well as evaluate whether integrated pest management (IPM) tools used in other crop systems can reduce virus reinfection in sweetpotato clean-seed production. Across three Louisiana sites in 2024-2025, alate aphids were monitored weekly using pan traps from June to October to determine the impact of soybean border rows and mechanistically distinct foliar spray tactics, including mineral oil, kaolin particle film, selective insecticides, and a plant defense activator. Virus incidence was assessed from slips prior to planting, from leaves during the season, and storage roots after harvest using multiplex RT-PCR detection of four sweetpotato potyviruses (SPFM, SPVG, SPVC, and SPV2). In addition, a controlled single-aphid transmission assay in potato evaluated whether behavior-modifying chemistries can reduce potyvirus transmission under standardized acquisition and inoculation conditions. Aphid captures occurred throughout the growing season at all sites, with peak captures generally occurring in July-August and September. Field results indicated that treatment performance depended on local inoculum source. Virus incidence was affected by treatment, but differences among individual spray treatments were not significant, while the soybean border showed only a marginal effect on reinfection. The most isolated site remained clean across sampling periods, highlighting how background inoculum source shape reinfection risk. In the controlled potato virus Y assay, all tested chemistries reduced infection relative to the untreated control (71.8%), with lower estimated infection under flonicamid (31.0%), flupyradifurone (9.8%), and VU041 (22.7%). Collectively, these findings support a layered IPM approach for field-based clean-seed, in which complementary tactics are combined to reduce aphid landing, probing and to slow infection accumulation by nonpersistently transmitted viruses.

Date

3-26-2026

Committee Chair

Davis, Jeffrey A.

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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