EFFECTS OF EVAPORATIVE COOLING ON GRAPE BUD HEAT SUMMATION AND ONTOGENY
in HortScienceThe major production risk for grapes on the Texas High Plains is freeze injury to buds and wood due to deacclimation brought about by warm periods in late winter. Delaying plant development by any means would reduce risk from injury. Reducing cumulative heat summation between rest and bloom has resulted in delayed bloom on peaches but internal rest is not expressed in grapes. An evaporative cooling system using microsprinklers was applied to a Cabernet Sauvignon vineyard during Jan.-April 1989. The system provided a 25 second wetting period at 3 minute intervals anytime air temperatures exceeded 10° C. Bud temperatures were monitored continuously with a data logger and correlated to cumulative budbreak and plant development. Significant bud cooling was achieved and by normal budbreak cooled buds lagged uncooled buds by 72% in degree days. A similar lag in budbreak was recorded early with some cooled buds breaking 3 weeks after most uncooled buds were open. Cooled plants continued to lag uncooled plants at bloom and even at harvest where oBrix and pH were lower and total acids higher from cooled plots.
