THERMAL ENVIRONMENT OF THE CITRUS RUST MITE

The distribution of citrus rust mite on individual fruit and in the whole citrus tree suggests an avoidance of solar exposure. A model of fruit temperatures as affected by solar radiation in different parts of the tree was constructed, and its predictions are compared with field temperatures and rust mite distribution patterns. The fruit temperature model is a function of latitude, time of year, time of day, fruit diameter and reflectance, position in the tree, atmospheric transmissivity and wind velocity. Where model predictions indicate unfavorable conditions, rust mite population levels were low. When the tree was divided into north-south, top-bottom quadrants, the north bottom quadrant had the most favorable temperatures and usually the most rust mites; the south bottom was also favorable and had high mite densities. The south top quadrant was least favorable often having temperatures in the lethal range, and it also had the lowest rust mite populations. © 1979.