The Breeding and Evaluation of Fine Fescue Species (Festuca spp.) for Tolerance to Tenacity Herbicide.

The fine fescues (Festuca spp.) are a complex cool-season turfgrass species that are popular in low maintenance situations due to their dense dark green color, low fertility requirement and tolerance to heat and drought. Tenacity is an herbicide with the active ingredient mesotrione that is used for pre and post emergent control of many broadleaf and grass weeds commonly found in turf stands. Mesotrione is in the HPPD inhibitor class of herbicides which target the plant enzyme 4-hydroxyphenylpyruvate dioxygenase. This enzyme is necessary for the biosynthesis of carotenoids which prevent the degradation of chlorophyll.  This herbicide is effective for controlling various weeds at seeding and planting of mature turf plants.  When tenacity is used at seeding on fine fescues the establishment and injury to those plants is very high which causes many problems establishing a turf stand.  The objective of this study is select and breed the fine fescue germplasm to increase the tolerance to tenacity. A nursery of hard fescue (Festuca brevipila), Chewings fescue (Festuca rubra subsp. commutata), and strong creeping red fescue (Festuca rubra ssp. rubra) was planted and evaluated for tenacity tolerance after three applications of Tenacity at 8 oz. per acre. Tolerant plants were selected and moved into crossing blocks to inter-pollinate and those progeny were planted in turf plots with various fine fescue controls and evaluated for tenacity resistance with a 6 oz per acre application of Tenacity at planting followed by a 4 oz per acre application of Tenacity 28 days after seedling emergence.