Sunburn damage is a skin discoloration of the exposed side of the fruit. Three different types of sunburn can be distinguished based the conditions of their formation;
- Sunburn browning is the most common type caused by the concomitant action of radiant heating and UV-B exposure. The symptoms are yellowish, brownish patches on the sun-exposed side of the fruit. Symptoms occur on the surface of the fruit (epidermis and hypodermis) but do not penetrate into the core tissues.
- Sunburn necrosis is
Burr knots are root initials that appear on the aboveground portion of the apple tree trunk. Some rootstocks, such as M.7, M.9, M.26, MM.106, and MM.111, are more prone to developing burr knots than others. Conditions that favor burr knot development include low light, high humidity, and temperatures between 68°F and 95°F.
Burr knots are problematic in a couple of ways. They can be an entry point for organisms, such as dogwood and plum borers, woolly apple aphids, fire blight …