Johnson’s Florist and Garden Center

Pest Bulletin #4

 

EUONYMUS SCALE

(Unaspis euonymi)

 

How to Identify Damage

• Euonymus scale is hard to detect in its early stages because no obvious damage results.

• Heavy infestations will mark the plant with thinning branches, yellow spotting of the leaves, and widespread presence of thin, white, waxy lines covering the leaves and stems.

• Close observation reveals black-brown scales present, primarily along the leaf mid-vein.

Life Cycle

Female scales overwinter on host plants and begin laying eggs beneath the waxy coverings in early spring. The eggs hatch over the course of several weeks, usually from mid- to late May to the end of June. Newly hatched nymphs crawl over the host plant or are transported by wind to other susceptible hosts. After they find an appropriate spot, they begin to feed and secrete a protective waxy covering. A second generation is produced in late summer, with eggs hatching late July through August. The fertilized females of the second generation pass the winter still attached to the host plant.

Critical Control Time

The best time for control is when the scales are in their newly hatched “crawler” stage.  They lack the defensive waxy covering of other stages and are more easily eliminated.  Target applications of horticultural oils or stronger pesticides during this period.

Control Strategies

Euonymus scale is very prevalent in the Washington metropolitan area. If you wish to plant the evergreen euonymus, you should plan to monitor your plant for this pest on a regular basis. Once a month during the growing season, you should examine your plants thoroughly for the presence of the white male scales. If you find them, prune that section of the plant off and destroy it. Consider planting alternative plants in your landscape that are not susceptible to this pest.

 

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