|Scientific Name||Phyllocoptruta oleivora (Ashmead)|
|Common Names||English: Citrus rust mite; German: Zitrus-Gallmilbe; Spanish: Acaro del tostado de los citricos; Italian: Acariosi dei limoni|
|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.|
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.
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.
In some areas, the citrus rust mite is considered the most important pest of citrus. Besides affecting the outer appearance of fruits (thereby rendering them unmarketable), extended feeding by P. oleivora can lead to reduced fruit size and weight, and to increased fruit drop. The juice content is reduced and its quality changes. Constantly high population densities can have a significant negative impact on plant health and growth.
Useful non-chemical contribution to Integrated Weed Management
If treatment is necessary, selective pesticides are to be preferred. Indiscriminate use of broad-spectrum insecticides may aggravate the situation.
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