Table of Contents

1. Southwest injury
2. Other topics in Other Pests and Disorders
   • Nematodes
   • Deer Control
   • Mouse and Vole Control in Orchards
   • Controlling Rabbits
   • Bird Control
   • Preventing Heat Stress and Fruit Sunburn on Apple and Pear Trees
3. Chapter 9 - Other Pests and Disorders - PDF 240 kb
4. Related Links

Southwest injury, or winter sunscald, occurs in the winter and is especially severe when cold, still nights follow cold sunny days. This phenomenon can occur in apple, peach, pear, cherry, plum, apricot and tree nut orchards. Injuries are usually confined to the south and southwest sides of the trunks and main scaffold branches. On sunny days these tissues become considerably warmer than the surrounding air and at night they cool rapidly. Under these conditions, freezing of the bark may occur. This injury usually affects large portions of the bark tissue that become brown and eventually slough off as healing occurs beneath.

In stone fruit orchards, these injuries provide ideal sites for infection by peach canker or other canker diseases. The combined effect of southwest injury and peach canker greatly reduces the productive life of affected trees.

Paint the trunk, crotches and lower parts of main scaffold branches with exterior white latex paint to minimize southwest injury. The white paint reduces the damage by reflecting direct sunlight on exposed tissue. This helps to prevent rapid warming on sunny days when air temperatures are below freezing.

Do not use oil-based or latex paints that contain any oil. These products contain toxic materials that may injure or kill fruit trees.

• October is the best time to apply the paint. Best results are obtained when trees are painted on days when the temperature is above 10°C and when spray will dry rapidly.
• Apply the paint by brush or by spray. If you choose spray, use 1-2 L of water/4.5 L of paint, depending on the thickness of the paint and the air pressure available.
• On young trees, paint the whole trunk. Only the south and southwest sides of older trees require paint. The whiter the bark after you paint, the greater the protection. Better quality paints are more durable.
• On young trees, injury from rodents may be a greater problem than southwest injury. To obtain protection from both problems, use commercially available thiram-latex mixtures, which reflect sunlight and act as a taste repellent for rodents.
• Do not use the thiram-latex mixture if you plan to use a fall Bordeaux spray program. The thiram reacts with the Bordeaux spray, changing the colour of the paint from white to brown and reducing its effectiveness as a heat reflector. The Bordeaux spray does not affect trees painted with latex only and can be used when thiram is excluded from the mixture.