Annual bluegrass (Poa annua) populations exhibit variation in germination response to temperature, photoperiod, and fenarimol

Laboratory studies were conducted to evaluate variation in germination response of eight annual bluegrass ecotypes (Augusta 4', 'Augusta 8', 'Augusta 14', 'Augusta 17', Auburn', 'Birmingham, 'Columbia, and Purchased') to photoperiod, temperature, and fenarimol, a fungicide-herbicide used for preemergence annual bluegrass. Seed collected from greenhouse-grown plants and stored for > 2 mo were evaluated under 18 environments (three day and night temperatures by six day and night durations). There was a significant ecotype by environment interaction affecting annual bluegrass germination. High temperature markedly restricted germination, with only the Birmingham ecotype exceeding 20% germination at day and night temperatures of 39 and 29 C, respectively. Maximum germination of all ecotypes was observed at a day and night temperature of 19 and 10 C, respectively. Maximum germination for a specific photoperiod was not consistent across ecotypes; however, all ecotypes germinated to some degree in complete darkness, which indicates that maintaining a dense turf canopy to eliminate annual bluegrass germination may not be completely effective. Ecotypes did not differ with respect to root length response to fenarimol but did vary with respect to shoot length response. Purchased and Columbia shoot growth were the most tolerant to increasing fenarimol concentrations. This information will be used to develop improved management strategies for annual bluegrass.