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Citrus Rust Mite

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Symptoms of damage of the citrus gall mite on citrus fruit.
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Symptoms of damage of the citrus rust mite on citrus fruits.

Scientific Name

Phyllocoptruta oleivora ASHMEAD

Biology

Description

The mites have the elongated body which is typical for members of the Eriophyidae. They are only 1.2 mm (0.047 inch) long and of light yellow color.

Damage

Due to their small size, the mites themselves do not attract attention. An attack of Citrus rust mite first becomes apparent when white spots appear on the fruits. The fruits later become darker, until they are completely brown; often, their surface roughens too. Different symptom levels are usually described by specific terms that vary between growing areas. Very common terms include „golden“ for light darkening, „black russet“ after a severe attack on young fruits, or „shark skin“, used to describe excessive rust mite damage on young grapefruits.
From a distance, infested fruits may look dull, as if covered with a fine dust, which in fact consists of a huge number of mite exuviae. Typically, the discoloration is more pronounced on the side of the fruit least exposed to the sun, as the mites avoid direct sunlight.

Lifecycle

Phyllocoptruta oleivora lives on the plant surface of Citrus spp., mainly on fruits and leaves. It destroys epidermal cells by injecting saliva and sucking out their contents. An individual female produces about 20-30 eggs, which are laid into pits and depressions, preferentially on the fruits but also on leaves or in small cracks in the bark of twigs. There are two larval stages, called protonymph and deutonymph. The generation time is about one week in summer and 2 weeks in winter, so the population density can soar under favourable conditions. The mites prefer warm and humid weather. However, all developmental stages can be found throughout the year; only reproduction is temporarily suspended during periods with low temperatures.

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