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White Prunicola Scale

| By | Pests

White Prunicola Scale (Pseudaulacaspis prunicola)

GDD Window (base 50): 707-1151

Overview:​​

  • Overwinter on bark as mated females​
  • Most infestations occur on the stems and major branches  ​
  • Armored scale, difficult to control due to long crawler emergence periods  ​
  • Second and third generations occur during early and late summer periods  ​
  • Indistinguishable from white peach scale without a compound microscope ​
  • Leaves a white ring of its outer margin when removed from bark or leaf tissue   ​
  • Mature females are circular & white with a yellow center, & is 1/16”  diameter  ​
  • Male covers are elongate, white, and up to 1/16” in length ​
  • Crawlers are salmon-colored​
  • Causes leaf yellowing, shedding, stunting, and branch death
  • Host plants: Prunus (flowering cherry), blue holly, lilac, & privet

Management:

Cultural Practices:
  • Natural predators:  brown lacewings, green lacewings, lady beetles, &  Parasitoid wasps ​
  • Prevent dusty conditions​
  • Reduce plant stress​
  • Dispose of heavily infested plants 
Materials:
  • Contact insecticides:​
    • Carbamates [1A]: carbaryl​
    • Pyrethroids [3A]: –thrins​
    • Organophosphates [1B]: acephate (translaminar), malathion​
  • Considerations:​
    • Will harm non-target species​
    • Timing is essential in controlling armored scales (target crawler stage before waxy covering forms)​
  • Systemic insecticides:​
    • Neonicotinoids [4A]: dinotefuran, acetamiprid, thiamethoxam​
    • Tetronic acids [23}: spirotetramat 
Biorationals:
  • Insecticidal soaps and Horticultural oils​
    • Neem oil​
  • Insect growth regulators:​
    • Pyriproxyfen [7A]​
    • Buprofezin [16]
With nursery container plants, the White Prunicola Scale on blue hollies is typically found infesting the lower branch stems near the base of the plant. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Close-up of the lower stems of a blue holly with an extreme infestation of White Prunicola Scale. Male scale covers have completely obscured the females scales. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Males scales have a white, elongated shape & the female scales are a circular shape with a yellow cast skin in the center. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Are these scales that require treatment? No! They are plant seeds that exuded oils, that turned white when dried & stuck to leaf. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Disclaimer – Materials do not cover all possible control scenarios and are intended for licensed professionals. Tradenames do not imply endorsement and are used as examples. You must strictly follow the label for each compound prior to use. Rutgers is not responsible form is used materials or damages thereof. The label is the law. Labels will provide detailed information on use and restrictions. Additionally, application intervals, compatibility, surfactant use, PHI, PPE, important and other key information is described in detail. Always discuss treatments with your local agents. Note: Neonicotinoids can only be legally applied in commercial agriculture settings by licensed applicators. Guidelines and recommendations made in this presentation are specific to the state of New Jersey.