The damage is characterized by the appearance on young leaves at the periphery of the tree of tiny gray or silvery specks, a process called stippling. Occasionally, fruits and twigs may also be affected. At high levels of infestation, these specks merge into spots that give the leaf or the green fruit a silvery or bronze appearance. The damage to the leaf tissues reduce the area used for photosynthesis and attacked tissue gradually decay. Premature leaf fall, twig dieback, reduced quality of fruits and decreased vigor of the trees can ensue. This is particularly the case during adverse environmental conditions, for example dry, windy weather. By contrast, a good water supply reduces the incidence and the damage caused by this pest.
Symptoms are caused by the feeding activity of the adults and nymphs of the citrus red mite Panonychus citri. They are characterized by a pear-shaped brick-red body and strong white hairs protruding from pearly spots on the back. They infect citrus trees and occasionally also other crops such as papaya, cassava or grapevine. It is found on both surfaces of leaves but appears mostly to feed on the upper surfaces. Thanks to the production of silk thread, it can be easily transported by wind to other trees. Insects and birds are other means of spreading. Infected tools and bad field practices can also propagate the pest to other fields. A good irrigation scheme with an optimal water supply for the trees reduces drastically the incidence and the damage caused by this pest. By contrast, low or high humidity, high wind, drought, or a poorly developed root system can worsen the situation. Optimal conditions for the citrus red mite are 25 °C and 50-70% humidity.
Panonychus citri has a large number of predators and other natural enemies, which is frequently sufficient to control its spread. Several phytoseiid mites (for example Euseius stipulatus) have been used in different countries for the effective control of the citrus red mite, when population numbers are still low. Some species of ladybird of the genus Stethorus feed voraciously on the pest. Fungi, and particularly viruses, also play a major role in controlling Panonychus citri populations in the field, something that may be influenced by temperature.
Always consider an integrated approach with preventive measures together with biological treatments if available. Selective pesticides are highly recommended, as broad-spectrum insecticides may aggravate the situation. For example, synthetic pyrethroids encourage outbreaks of this mite. The use of several types of acaricides avoids the development of resistance.