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White Prunicola Scale (WPS)

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Pseudaulacaspis prunicola
Written by: 
Jaime Pinero

Overview

White Prunicola Scale (WPS) is a serious pest of Prunus, especially in temperate areas. In upstate NY orchards, Cornell University researchers  have reported the presence of WPS, which seems to be a closely related species of White Peach Scale (Pseudaulacaspis pentagona) found in the southeastern United States. The WPS is more common in temperate climatic zones.

Infestations are characterized by numerous white scales that cluster on the trunk and scaffolds, giving them a whitewashed appearance. Feeding reduces tree vigor, and foliage of affected trees may become sparse and yellow. Heavy infestations can cause death of twigs, branches and entire trees if left unattended.

Biology

WPS overwinters as an adult female and deposits eggs in the spring. In northern Pennsylvania, the scale is bivoltine (two generations per year).  

Monitoring

Monitor crawler emergence with black electrician's tape wrapped around scale infested branches with the sticky side out. A thin coating of petroleum jelly will enhance and extend the tape's effectiveness in capturing crawlers.

Management

Horticultural oil is recommended as a dormant spray in April, and insecticides can be used against crawlers in mid-June through early July (about 700–1150 DD base 50°F from March 1).