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San Jose Scale Insect


San Jose Scale Insect

Usually appear in

Spring to Autumn.

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Caused By:-     The Scale Insect Quadraspidiotus perniciosus


The San Jose scale Quadraspidiotus perniciosus (Aspidiotus perniciosus, Comstockaspis perniciosa, Diaspidiotus perniciosus) insect is an extremely important pest pest of Apple, Peach, Pear and Plums and many more trees and plants. It is a quarantine pest in some countries.
Originating in the Siberia, north east China and the northern part of the Korean peninsula. it was introduced into California's San Jose Valley on infested plant stock from China around 1870.
It may have up to 3 generations per year, depending on climate and weather.
It is a sucking insect that injects a toxin into the plant as it feeds causing a reddish purple ring surrounding each spot where a scale settled on the fruits.
They can be found on the trunks, branches, twigs, leaves and fruits of the plant. Females predominate on the leaf stalks and fruit while males predominate on the leaves.
Infestations will cause decline in tree vigour, growth, and productivity and left uncontrolled, they will kill the entire tree in a couple years.
They overwinter as immature scales, although in mild years some adult mated females may also survive. In the spring, the tiny winged males emerge and mate with the wingless females, and about one month later the first crawlers can be seen, usually between between May and June.
Eggs are not seen because females give birth to live, extremely small, flattened, yellowish crawlers, which move to other parts of the tree before settling down permanently. A few days after settling down, crawlers will secrete a waxy covering over their body that will protect them from pesticides.
When the males mature a tiny, yellow winged males emerges from under the scale and will seek out females and the cycle will begin again.
The adult female is yellow and is covered with a rounded dark grey scale up to 2mm in diameter. Adult male are about 1 mm long and golden brown in colour.
This species is found in both temperate and subtropical climates.
Picture by United States National Collection of Scale Insects Photographs Archive, USDA Agricultural Research Service,
See these other Scale insects Azalea Bark, Azalea Cottony, Beech Bark, Brown, Eucalyptus Gumtree, Euonymus Mussel, Hemispherical, Horse Chestnut, Hydrangea, Juniper, Mussel, Oleander, Scale, Soft, Viburnum Cushion, Wisteria, Wooly Vine.


Insecticidal sprays applied to developing overwintered individuals, first flight males, or first generation crawlers will give good control.
Natural enemies that feed on these scale insects include two predaceous beetles: ladybird beetle, Chilocorus orbus, and another small beetle, Cybocephalus californicus along with several chalcid wasps which are known to parasitise this scale insect if they are not killed by insecticides, but they do not give full control.
Spraying in the dormant season with a winter tar wash or insecticidal or horticultural oil will help reduce this pest.
Pheromone traps and double-sided sticky tape can be used to monitor crawlers in April and May.

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