Issue link: https://read.dmtmag.com/i/333548
w w w. v w m m e d i a . c o m J u l y - A u g 2 014 | V I N E YA R D & W I N E RY M A N A G E M E N T 3 7 eat damage can reduce both yields and quality in the vineyard. The effect of heat waves depends on the phe- nological stage and vine water status of the vines at the time of the occurrence, as well as the severity and duration of the heat wave. From bud break through flowering, flower parts are susceptible to damage from extreme heat, which can result in poor set and reduced yields. After set, grapes become increasingly susceptible to heat damage. Red grapes, after verai- son in particular, can experience tempera- tures significantly higher than their surrounding air temperature. Heat damage can cause grape sunburn or shrivel, negatively affecting both quality and yield, as well as chemical changes that can negatively affect flavor, color and quality. The temperature of a grape cluster is affected by ambient air tempera- ture, absorbed radiation, and cooling from evapo- transpiration, which are in turn affected by vine water status, relative humidity, wind velocity, solar radia- tion and cluster exposure. Additionally, cluster mor- phology, berry size and color also modulate cluster temperature. G r e e n b e r r i e s b e f o r e veraison and white grapes after veraison do not get as hot as dark berries when exposed to similar condi- tions. This is related to varying rates of light reflec- + Heat damage can cause grape sunburn or shrivel, hurting both quality and yield. + Optimal row orientation and trellis design can mitigate the negative impact of heat waves. + Transpiration has a cooling effect on plants; it is the role of the viticulturist to encourage this in periods of high heat. + Irrigation and canopy man- agement strategies can be utilized to protect vines dur- ing heat waves. + Shade cloth, sprinklers and misters should be consid- ered in high-risk sites. AT A GLANCE RELIEF FROM the Heat Various tactics protect vines from searing temperatures Photo: Thinkstock/deyangeorgiev SOIL & CELLAR REMI COHEN