Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Plants, Soils, and Insects

Major Professor

Thomas C. Mueller

Committee Members

John C. Sorochan, Carl E. Sams, Thomas J. Samples, William E. Hart


Dura Blue™ and Thermal Blue™ hybrid bluegrass (Poa arachnifera Torr. x Poa pratensis L.) have been selected for increased heat and drought tolerance and offer an alternative to traditional Kentucky bluegrass and tall fescue in the transition zone. Dura Blue and Thermal Blue were compared to Apollo™ Kentucky bluegrass, Dynasty™ tall fescue, and Kentucky 31 tall fescue. All turfgrass species tested were acceptable for use in the transition zone. Thermal Blue should be seeded from 50 to 150 kg seed/ha. Thermal Blue should be seeded in September for highest quality and most rapid turf cover. However, January and April provided complete turf cover 7 months after seeding. Thermal Blue should be fertilized with 100 to 300 kg N/ha/yr. However, higher nitrogen fertility reduced turf quality in late summer and early fall. Thermal blue can be mowed at heights from 20 to 50 mm, although, mowing heights should be ≥ 35 mm to avoid decreased turf quality in the late summer and fall. Applications of the plant growth regulators ethephon and paclobutrazol caused injury to Thermal Blue during the summer and should be avoided. Thermal Blue exhibited a significant reduction in cover (>57%) from dithiopyr, oryzalin, oxadiazon, pendimethalin, prodiamine, quinclorac, and trifluralin applied at turf seeding. Postemergence applications of foramsulfuron and trifloxysulfuron on established Thermal Blue decreased turf quality and caused unacceptable injury (>15%). Established Thermal Blue treated with clethodim, fluazifop- p-butyl, and sethoxydim showed decreased quality and unacceptable injury (>15%). Hybrid bluegrass is thought to have increased heat tolerance based on greater total nonstructural carbohydrate (TNC) accumulation. Thermal Blue hybrid bluegrass, Apollo Kentucky bluegrass, Supranova™ supina bluegrass, and Laser™ rough bluegrass showed linear decreases in TNC accumulation in the leaves from April to July. However, hybrid bluegrass and Kentucky bluegrass showed a linear increase in TNC accumulation in the roots from April to July. This research indicated that hybrid bluegrass and Kentucky bluegrass may have more heat tolerance due to a reallocation of TNC from the leaves in April to the roots in July.

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