Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2019
Publication Date: 4/22/2019
Citation: Doherty, E.M., Meagher Jr, R.L., Dale, A.G. 2019. Turfgrass cultivar diversity provides associational resistance in the absence of pest resistant cultivars. Environmental Entomology. 48(3):623-632. https://doi.org/10.1093/ee/nvz026.
DOI: https://doi.org/10.1093/ee/nvz026

Interpretive Summary: Fall armyworm (FAW) is a serious lepidopteran pest of agricultural crops such as maize, sorghum, cotton, and rice in North America. One strain of FAW caterpillars also feed on turf and pasture grasses. In Florida, St. Augustine grass is a main turfgrass species that is found in lawns and public areas and suffers attack from FAW. Researchers from the University of Florida, in collaboration with a scientist from USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, assessed feeding damage produced by larval stages of FAW caterpillars on various St. Augustine grass varieties. No single St. Augustine grass variety was found to have resistance to FAW caterpillar feeding. However, having a mixture of varieties reduced larval feeding damage and resulted in a reduction in pest fitness. The results suggest that warm season turfgrass variety diversity may be a viable integrated pest management option for reducing damage to the grass and lowering FAW populations.

Technical Abstract: Turfgrasses are ubiquitous in urban landscapes and can provide numerous ecosystem services. However, most warm season turfgrasses are produced, planted, and maintained as cultivar monocultures, which may predispose them to herbivore attack and reduce the services lawns provide. Turfgrass breeders and managers historically employ host plant resistance as a strategy to reduce herbivory and preserve beneficial services. Increasing turfgrass cultivar diversity may provide similar or greater benefits through associational resistance while conserving desirable maintenance and aesthetic traits. However, no studies have examined this in warm season turfgrasses. To address this, we evaluated host plant resistance to fall armyworm (Spodoptera frugiperda [J.E. Smith]) in commercially available cultivars of St. Augustinegrass (Stenotaphrum secundatum) and then investigated if the resistance or susceptibility of S. secundatum cultivars carried over in mixed cultivar plantings. Through a no-choice diet mixing study and a limited-choice greenhouse study, we detected no host plant resistance in monocultures of S. secundatum cultivars. However, we did find that as cultivar diversity increased, female S. frugiperda larval weight and herbivory decreased. Additionally, choice tests indicated that larvae prefer less diverse stands of S. secundatum cultivars. Interestingly, our results suggest that in the absence of host plant resistance, warm season turfgrass cultivar diversity may reduce herbivore pest fitness and damage. These results demonstrate that warm season turfgrass cultivar diversity may be a viable integrated pest management tool, which warrants further investigation.