Odd-looking white spots on a pachysandra bed often indicate a euonymus scale infestation. This pest, although uncommon on pachysandra, is known to harm plants by feeding on plant sap with piercing-sucking mouthparts. Protecting the adult insects with a covering makes controlling them with insecticides challenging.
While action is not immediately necessary, it’s vital to manage the infestation once the pest’s population grows. The female scale insects remain on plants over winter and begin laying eggs in late April through May. Crawlers emerge over a two-to-three-week span.
Males inhabit a narrow white waxy coating and mate with females in spring. Crawlers roam the plants briefly before feeding and forming their own waxy covering. A second generation occurs from late July through August.
Intervention is most effective in the crawler stage. Pruning infested areas of the pachysandra in March helps remove overwintering females. Debris should be disposed of in garbage or commercial landscape waste sites for composting. This process helps kill the insects through high-heat treatments.
Crawlers are active from late May to early June and late July through August, providing prime opportunities for control measures. Removing overwintering adults reduces pest populations significantly.
Applying a summer-weight dormant oil during crawler stages offers additional control.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at [email protected].
Tim Johnson, senior director of horticulture at the Chicago Botanic Garden, shares these insights.
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