Scale Insect Problems on Hemlocks

Elongate hemlock scale on Fraser fir

Hemock woolly adelgid has captured much of the press in recent years regarding our eastern hemlocks. There has, however, been a noticeable increase in the presence of another insect pest of hemlocks in the last few years.  Elongate hemlock scale, an armored or hard scale, is being found more frequently here in parts of the Northeast not only on hemlocks (both eastern and Carolina) but also on other coniferous trees such as Fraser firs.  Mature female scales are yellowish to brownish while mature males are white. Both are elongate in shape and around 2 mm in length. Scales are typically found on the undersides of needles.  There is one generation here in the Northeast with egg hatch occurring in late spring.  The young nymphal stage (crawlers) emerge over the course of several weeks.  Treatments can be applies as sprays (dormant oil & crawler stage) or as subsurface systemic applications.

Circular hemlock scale

Another scale that is also being seen more frequently in the southern part of the Northeast is circular hemlock scale. This scale manifests itself as small, raised, dark colored shells of mature females primarily on the undersides of needles. Spruces can also be infested. The life cycle and controls are similar to elongate hemlock scale.

Both these scales can cause needle yellowing, needle drop and possible branch death.  Yellowing of needles during the growing season is one of the first symptoms although this should not be confused with seasonal needle drop.  Control is important before major foliage loss occurs which can weaken trees and result in branch

Needle yellowing from scale insect feeding

death.