The Purdue Plant and Pest Diagnostic Laboratory

What's Hot at the P&PDL for
May 10, 2010

Frost Injury in Grapes

Bruce Bordelon, Extension Specialist, Department of Horticulture and Landscape Architecture, Purdue University

Grapes are very sensitive to frost damage and there have been several instances of light frost across the region this spring. Damage is showing up in commercial plantings and some home gardens. Frost damage often gets misidentified as herbicide injury because other plants may not show typical signs of freeze injury. Grapes are more sensitive than many other plants.

The tolerance of grape tissue to cold temperatures is relative to their stage of growth. A bud that is just swelling can tolerate temperatures in the low 20s with little damage. But as soon as the bud has broken and the leaves unfold, the tissue is sensitive to temperatures of 28-30°F. Varieties may also vary in their response to freezing temperatures.

Damage usually shows up as wilted shoot tips and brown leaves (See Picture 1). When temperatures are cold enough, all shoot tissue is completely killed (See Picture 2). However, in many cases temperatures are just at the lethal point and the shoot may not be completely killed. Some leaves may turn brown and dry out, but older leaves may remain alive and display a pattern of angular flecking with sectors of yellow, white and green (See Picture 3). It is not unusual to see healthy, undamaged shoots next to damaged ones (See Picture 4).

In most cases the vines will recover as secondary buds at the base of the damaged shoot will break and produce healthy shoots for this growing season (See Picture 5).  These shoots are seldom as fruitful as the original primary shoots, so fruit yields will be greatly reduced this year.

Click image to enlarge

Wilted shoot tips and brown leaves

Picture 1

Dead tissue

Picture 2

Grape leaf yellowing

Picture 3

Healthy shoots next to damaged

Picture 4

Healthy shoots emerging

Picture 5

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service