The San Jose Scale (Quadraspidiotus perniciosus) was described in California during the year 1880.
It affects more than 150 plant species, among them the stone fruit trees (cherry tree, almond, peach, apricot, plum, nectarine. ..) and nugget (pear, apple tree, quince).
This plague of the cherry tree , is also known for caspilla or pernicious black scale
Quadraspidiotus perniciosus does not affect the citrus fruit or the olive tree, these are parasitized by other species of woodlice.
This is the case of the Lapilla or citrus flea that affects lemon trees, orange trees, mandarinos… and the Caparreta or black scale of the olive tree .
The excretions of these black scale are the ideal substrate for the Bold or sooty .
Although the Quadraspidiotus perniciosus does not cause damage to citrus fruits, some treatments and cultural measures are compatible with the control of the citrus flea.
Curiosities: It receives the name of plague or San Jose Scale due to the zone where the plague was discovered. The plantations of the Californian city of San Jose, were the first to be affected by this virulent plague of Asian origin.
Quadraspidiotus perniciosus description
Probably, Quadraspidiotus perniciosus is plague plus destructive and virulent of black scale. Although winter oil treatments control this disease, these are not always done by farmers. The black scale is fixed on branches, leaves and fruits of fruit trees, sucking the sap and drying branches and trees completely.
By feeding on fruits, the San Jose plague produces red spots on the skin that devalue the fruit.
They present three generations per year. The larvae that have hibernated return their activity in spring, reaching their adult stage in April-May and giving rise to the first generation.
1st Generation at the end of May, beginning of June.
2nd Generation takes place at the end of July-beginning of August.
3rd Generation at the end of September, beginning of November.
Damage caused by Quadraspidiotus perniciosus
After the attacks of Quadraspidiotus perniciosus, their populations cover the branches, leaves and fruits if there were shields.
As a consequence of the sucked sap, the tree weakens and the harvest is reduced.
The black scale, when placed on the trunk, obstructs the stomata (cells responsible for respiration and capture of CO2).
The Bites of the Quadraspidiotus perniciosus are toxic and wither the affected area.
The fruit reduces its commercial value due to the visible spots on the skin and the presence of the black scale.
In small fruit trees and even large trees. When control techniques are not carried out after several campaigns of Quadraspidiotus perniciosus attacks, the populations reach levels that can dry the tree completely.
Curiosities: This species of black scale does not excrete molasses.
Control of San Jose Scale
The application of chemical treatments allows effective control of San Jose Scale.
The treatment with winter oil is probably the most adequate and economical. The oil works by contact, creating a film that prevents the black scale breathing and suffocation. This application also helps to reduce the wintering populations of aphid .
The paraffin oil to 83% is the product authorized by the ministry, is marketed under the name PROMANAL AGRO.
Within the treatments with insecticides. The following active matters are authorized for the control of the Quadraspidiotus perniciosus on November 3, 2017:
Buprofezin 23.4%, Buprofezin 25%, Deltametrin 1.57%, Deltametrin 2.5%, Fenoxicarb 25%, Methyl Chlorpyrifos 22.4%, Piriproxifen 10% and Calcium Polysulfide 18.5% .
A significant part of the information, comes from Spanish research organizations. When phytosanitary products are used, it is important to verify that their use is currently authorized in the country of application.