Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Plant and Environmental Science

Committee Chair/Advisor

Joseph Roberts

Committee Member

Haibo Liu

Committee Member

Churamani Khanal

Abstract

The root-knot nematode (Meloidogyne spp., RKN) is a common plant-parasitic nematode (PPN) associated with hybrid bermudagrass [Cynodon dactylon × C. transvaalensis ‘Miniverde’] in the Carolinas. Severe outbreaks of take-all root rot (TARR), a recently described bermudagrass disease caused by multiple fungal species, are frequently linked to high PPN populations despite well-timed fungicide and nematicide applications. These recurring outbreaks highlight the need for improved understanding of pathogen interactions and alternative management strategies. The objectives of this research were to (1) evaluate the interaction between RKN and TARR on hybrid bermudagrass quality and (2) assess Bacillus firmus strain I-1582 (Votivo SC, BASF) as a bionematicide for RKN management. A greenhouse co-inoculation study examined individual and combined pathogen effects on turfgrass quality. Two additional experiments evaluated B. firmus I-1582 rhizosphere colonization across root-zone mixtures and its field efficacy relative to synthetic nematicides. Results indicated that turfgrass exposed to multiple pathogens declined more rapidly than turfgrass exposed to a single pathogen. Rhizosphere colonization in a greenhouse setting moderately favored organic matter-rich root-zone mixtures and application frequency had no consistent effect on B. firmus accumulation. While B. firmus alone was insufficient as a stand-alone management strategy, integrating a bionematicide with reduced-rate synthetic nematicides provided RKN control comparable to full labeled rates, while potentially offering environmental, economic, and turfgrass health benefits.

Author ORCID Identifier

0000-0001-9193-3153

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