In the past, Lecanium (Lecanium fletcheri) spp. of scales found on Taxus have been assumed to be L. fletcheri. However, Lecanium fletcheri is reported to have only one generation per year; while a common Lecanium scale found on Taxus
plants has two generations per year. In some places in Michigan and nearby a Lecanium spp. on Taxus has one generation per year.
All Taxus species. Also, a similar scale is found on arborvitae.
The first generation crawlers emerge from June 10-30, settle on the needles and twigs and feed until August when they are nearly mature. A second generation of crawlers emerges in September. These young scales will mature in May.
Look for small (3-5 mm), brown hemispherical scales on inner foliage and twigs of Taxus plants. Young immature scales are even smaller, flat and clear.
Only apply insecticides to Taxus if the scale population is too high (greater than 15% of samples. are infested). Parasites and predators regulate scale populations. Parasites are most effective along field borders. Biological control has good potential in production nurseries as well. .
Dursban or Talstar in early October if scales can be found on more than one of 10 leaf samples examined in August. If an unacceptable level of live scale is still found in April or early May, another application can be made at that time. Early July is the next best time to apply an insecticide. However, because of a second generation, a July spray without an October spray is risky.
Information obtained through Michigan State Extension, Landscape CAT Alert 61094006