- Citrus

Citrus Citrus

Citrus Hindu Mite

Mite

Schizotetranychus hindustanicus


In a Nutshell

  • Numerous and minute gray or silvery specks appear on leaves.
  • Attacked tissue usually has a silvery appearance from the distance.
  • Heavy infestations lead to premature leaf fall, twig dieback, reduced quality of fruits and decreased vigor of the trees.
  • A good water supply reduces the incidence and the damage caused by this pest.

Symptoms

The damage is characterized by the appearance on the upper surface of leaves of tiny gray or silvery specks, a process called stippling. These are usually more numerous along the midrib and later extend to the entire leaf blade. Usually, leaves fruits and twigs at the periphery of the tree are more likely to be attacked. At high levels of infestation, these specks merge into larger spots that give the leaf or the green fruit a uniform silvery or bronze appearance. The attacked tissue gradually harden and decay, leading to premature leaf fall, twig dieback, reduced quality of fruits and decreased vigor of the trees. 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.

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Hosts

Trigger

Symptoms are caused by the feeding activity of the adults and nymphs of the citrus Hindu mite Schizotetranychus hindustanicus. They are characterized by peculiar web nests (1-3 mm in diameter) that females produce on the underside of leaves and under which the colony develops. This characteristic differentiate them from other mites and give them their other common name 'nest-webbing mite'. Adults move out of the nest and attack other leaves or fruit tissues, while immature stages prefer to settle under the web. Insects and birds may transport and spread the mites to other trees. 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.

Organic Control

Schizotetranychus hindustanicus has a large number of predators and other natural enemies, which is frequently sufficient to control its spread if weather conditions are unfavorable for the insect. Because of the web nests, phytoseiid mites (for example Euseius stipulatus) are not effective against this mite. Some species of ladybird of the genus Stethorus feed voraciously on the pest. Fungi, and particularly viruses, also play a major role in controlling populations in the field, something that may be influenced by temperature.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Selective pesticides are highly recommended, as broad-spectrum insecticides, by killing predators and other beneficial insects, may aggravate the situation. A rotation of several types of acaricides avoids the development of resistance.

Preventive Measures

  • Monitor the orchards with a lens regularly to assess numbers of mites.
  • Avoid an excessive use of pesticides as this can influence negatively the populations of beneficial insects.
  • Water the tree properly and avoid drought stress.
  • Avoid contact of branches with grasses or weeds on the ground.
  • Keep the orchard clean of weeds.
  • Remove waste and debris after harvest.

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