Investigating white grub tolerance in turf-type tall fescue

Tall fescue is a cool-season, bunch-type perennial grass that is native to Europe and Africa and introduced to the U.S. in the 1600s. It gained popularity in 1940 after the release of the first commercial cultivar, ‘Kentucky-31’. Since then, hundreds of turf-type tall fescue cultivars have been developed. Tall fescue has gained popularity due to its tolerance to heat and drought, insects, shade, and good performance with minimal maintenance. Because of these strengths, tall fescue has become the major cool-season turfgrass species used in home lawns and recreational fields, athletic fields, and golf courses throughout the northern U.S. and transition zone. The turfgrass breeding program at Rutgers University has focused on producing tall fescue cultivars with superior turf quality characteristics, sustaining endophyte infection through seed production, and building tolerance to abiotic stresses (e.g., drought, heat, and shade) and biotic stresses (e.g., disease and insects). A complex of white grubs, including the oriental beetle, Japanese beetle, northern masked chafer, and Asiatic garden beetle, are the most destructive and widespread turfgrass insect pest in the northeastern U.S. A lot of research has been conducted on the impact of white grubs on turfgrass and their cultural, chemical and biological control, but little has been done to understand the potential for breeding for tolerance to white grub feeding. Research goals were to investigate white grub tolerance in turf-type tall fescue. This was accomplished through a field trial and series of growth chamber experiments. The field trial was used to determine if white grub densities impacted turf quality, if there were any differences in white grub population development among cultivars with and without endophyte, and if there was mortality among the different cultivars. The growth chamber experiments evaluated the ability of plants to recover from and regrow roots in a controlled environment simulating white grub herbivory via root severing and a drought study to determine if drought tolerance correlates to white grub tolerance. Plants in the field trial and growth chamber experiments were evaluated for endophyte presence to determine any associations with white grub herbivory. In the field trial, cultivar/experimental selection had a significant effect on turf quality and percent endophyte of each cultivar had a strong positive correlation with turf quality. However, white grub densities and development were not significantly affected by cultivar/experimental selection. The root cutting study simulating white grub herbivory showed that cultivar had a significant effect on plant growth traits and root morphological traits including dry shoot biomass, shoot length, root surface area, and root volume. However, Epichloë endophyte infection did not have a significant effect on any plant traits. The drought study showed that cultivar/experimental selection had a significant effect regarding visual drought tolerance and plant measurements. However, Epichloë endophyte did not have a significant effect. These findings will help to better understand the interaction between white grubs and turf-type tall fescue and aid plant breeders in the production of insect tolerant cultivars.