Physiological disorders in loquat (Eriobotrya japonica Lindl.).
Studies were conducted [date not given] to identify some of the factors contributing to the high incidence of plant disorders in loquat in Israel. A survey of russet incidence in different loquat plantations revealed that the percentage of russeted fruits was significantly higher in exposed orchards compared to trees grown under a black net cover. Shading trials, followed by both temperature and irradiance measurement, showed a positive polynomial increase in the percentage of russet with increasing temperature, and a parabolic function in relation to irradiance. The fresh weight gain of loquat fruits followed a two-phase discontinuous polynomial growth rate. Fruit growth rate under black net cover of 40% shade lagged initially after the fruit growth rate on exposed trees. Russet was first detected at 41 days after fruit set. In net-covered plots, the percentage of fruits with russet spots increased steadily at a slow rate, reaching 15% at 111 days from fruit set. In exposed fruits, a sharp increase in russet incidence was observed between days 54 and 76. Russet incidence in exposed fruits reached 42% at harvest. Purple spots decreased linearly as the number of fruits per cluster increased. Defoliation was used to establish different fruit leaf ratios. Purple spot incidence increased from 25 to 65% as leaf area per fruit increased.