Screening Rhizobacteria for Control of Fall Armyworm in Turfgrass

Abstract

Fall Armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is regarded as one of the most devastating noctuid pests in America. FAW larvae are especially detrimental to turfgrass, as foliar feeding results in an array of visually unappealing symptoms. Traditional pest control methods rely heavily on synthetic insecticides, raising concerns about environmental impact and resistance issues. The growing need to reduce synthetic chemical use in agriculture has driven the search for sustainable alternatives in both fertilizer and pest management. This study explored two approaches for the selective control of FAW larvae in turfgrass: (1) screening a library of Plant Growth-Promoting Rhizobacteria (PGPR) for strains with insecticidal activity, and (2) engineering turfgrass-specific endophytes to express Cry proteins from Bacillus thuringiensis (Bt), a soil dwelling bacterium known for its ability to produce toxins that target various insects. In the first approach, a total of 72 PGPR strains were screened for their effectiveness against FAW larvae. One strain, JM-362 (Serratia marcescens), was identified as a promising candidate, showing strong insecticidal activity and demonstrating potential for biocontrol of FAW. In the second approach, efforts to genetically engineer Blend 20, a group of turfgrass-specific PGPR strains, to express a custom vector encoding a Cry1Fa gene were unsuccessful despite multiple transformation attempts. Although the engineering approach did not achieve its intended goal, the identification of PGPR strain JM-362 as a biocontrol agent presents a viable alternative to chemical pesticides. This work provides a foundational screening platform for identifying PGPR with innate insecticidal activity against FAW and highlights important technical barriers to transformation in Bacillus species.