Flower Bud Winter Damage of Stone Fruit In New Mexico During 2011

Late frosts are the primary issue limiting fruit production in central and northern New Mexico and nearby states. But in 2011, a cold snap occurred around January 1 and another severe one in early February with minimum temperatures reaching -7.2 °F (-21.8 °C, Jan. 1) and -11.3 °F (-24.1 °C, Feb. 3) at Alcalde in northern NM, and 4.8 °F (-15.1 °C, Jan. 1) and -13.9 °F (-25.5 °C, Feb. 3) at Los Lunas in central NM.  At Alcalde, 10 days after the -7.2 °F (-21.8 °C) on January 1, 400-1000 flower buds per cultivar of peach and apricot were dissected and evaluated for their survival rate with brown/black flower primordia considered dead and greenish flower primordia considered as live. Live flower bud percentage varied by cultivar for peach, ranging from 11% for ‘Blazing Star,’ 25% for ‘PF-1’ to 85% for ‘Encore’ and 87% for ‘China Pearl.’ Flower buds of apricots were hardier than peaches with ‘Perfection’ showing 70% survival, 97% for ‘Sunglo’ and 99% for ‘Harglow.’ Later in the season, peaches and apricots were evaluated with the same criteria, and plums were judged near bloom with swelling buds/flowers considered as live and no swelling buds as dead. After the early February freeze, peach flower buds were severely damaged from central to northern New Mexico. Twelve peach cultivars were dissected and evaluated on Feb 11, 2011 at Alcalde, NM. Flower primordia were all brown/black in color with fewer cultivars showing less than 1% survival. Based on the above information, the 10% kill of flower buds for most peach cultivars occurred at temperatures higher than -7.2 °F (-21.8 °C) and 90% kill occurred between -7.2 °F (-21.8 °C) to -11.3 °F (-24.1 °C). Peach vegetative buds were safe for all cultivars. Apricots survived better than peaches. The flower buds on spurs or shoots of lower canopy of ‘Perfection’ and ‘Puget Gold’ had 0% survival and less than 1% for ‘Goldcot.’ But ‘Harglow,’ ‘Harlayne,’ and ‘Sunglo’ had 8-15% survival.  For vigorous shoots at the upper canopy, apricot flower buds on one-year shoots had higher blooming rate than those on spurs of second-year or older wood. Flower buds of Japanese plums were also damaged severely (less than 0.2% survival for ‘Santa Rosa’ and 4.8% for ‘Methley’), but European plums were safe with over 98% flower bud survival for ‘Castleton’ and ‘NY6’ and 87% for ‘Stanley’ after -11.3 °F  at Alcalde.