One of the most filthiest scale insect pests known to horticulturalists, the Euonymus scale (Unaspis euonymi) is a tiny little armored scale that covets evergreen Euonymus fortunei in the garden or landscape. Adult females have a dark cover that is wider at the posterior end, sea-shell in appearance with white margins. The smaller males have a white, narrow cover and they resemble white flecks with the naked eye.
The good news is, the crawlers have hatched and are starting to colonize feeding sites on 2016 shoots. The tiny little orange crawlers can be found on shoots and leaf undersides. Crawlers look like “eggs with legs”. And they are at their most vulnerable life stage.
Once they settle (above), crawlers lose their legs and become “nymphs”. They also become a duller orange-brown. They become more ridged looking and enlarge as they grow while sucking plant juice from the mouthparts on the under side of their heads.
Crawlers and newly settled nymphs are susceptible to insecticides, including insecticidal soap, the summer rate of horticultural oil, Lagon and Orthene. Kontos is a new insecticide for Euonymus scale that can also be used as a container soil drench (a great alternative to foliar spraying).
The dead adult (above) scales will often persist on stems and leaves, long after they have died…giving the plant an appearance of severe infestation. Usually the dead scales are washed off by rain over time. Applications of water or the summer rate of horticultural oil may help speed up that process.
A second generation of crawlers usually appears about 6-7 weeks after the first, depending on how warm their location is. So mark your calendars appropriately for a second generation around the second week of August.
Where Fletcher scale (taxus scale, Parthenolecanium fletcheri) has been a problem in the past, monitor for dark brown “bumps” on twigs and needles of Eastern white cedar (Thuja occidentalis) or yews (Taxus spp.).
Some of those eggs will have legs (click here for video) and will be crawling looking for tender new growth to feed on.
Several insecticides are registered for management of Taxus scale crawlers in the nursery. Try insecticidal soap in the landscape. The summer rate of horticultural oil may be phytotoxic on some hosts, especially when temperatures are > 26C.