Severe scale crawler infestation on Scotch pine, along with a heavy amount of sooty mold (black coating on stem and needles). Courtesy of Brian Schildt, PDA
Toumeyella pini (King)
- Two- and three-needled pines, especially Scotch
Symptoms and Signs
- Black sooty mold on surface of bark and needles; tree may appear darker from distance
- Clusters of brown and white, helmet-shaped scales on branches
- Presence of stinging insects in and on trees
- Reduced plant vigor
Causes of Similar Symptoms
- Pine tortoise scale
- Cinara aphids
Note: Many previous reports of pine tortoise scale (Toumeyella parvicornis Cockerell) in Pennsylvania actually refer to this closely related species. Striped pine scale is the more common of the two species in Pennsylvania.
The striped pine scale is a soft scale found on the new growth of pines. The coverings of adult female scales resemble miniature helmets. They are reddish brown and may appear to have one or more cream or white stripes centrally. This coloration varies with age and condition of the scales. The coverings of mature females are ¼ inch (6.3 mm) long. They are generally found in clusters on the outer twigs of host trees. Nymphs or crawlers of this scale are tan to orange and will be found on the twigs and needles of new growth. As this insect feeds on the bark of pines, it excretes a sugary liquid known as honeydew (Figure 1).
Figure 1. Striped pine scale excreting a drop of honeydew. Courtesy of Brian Schildt, PDA
Black sooty mold will grow on the bark and needles coated with the honeydew, giving the tree a darkened appearance (Figure 2). Frequently, ants, bees, and wasps will be found feeding on this honeydew. A heavy buildup of sooty mold results in stunting and chlorotic growth.
Figure 2. Black sooty mold development resulting from honeydew excretion. Courtesy of R. Scott Cameron, Advanced Forest Protection, Inc., Bugwood.org (#3226096)
Calendar of Activities
Biology and Life Cycle
Striped pine scale has a single generation each year in Pennsylvania. Fertilized, immature females can be found on twigs of the most recent season’s growth (Figure 3). Occasionally, a few mature females may also be seen overwintering for a second season on last year’s growth. In early spring, the overwintering nymphs resume feeding and mature. Females deposit eggs under their helmet- or tortoise-shaped covering in early summer. These eggs, which may number in the hundreds, will hatch over a period of several weeks in late June or early July. The newly hatched nymphs, or crawlers, are very active (Figure 4). They quickly move to the new expanding growth and can even be found on the ground under trees. Crawlers can attach to insects, birds, animals, people, and machinery and be easily moved to uninfested trees. Within a day or two, the newly emerged crawlers molt, losing their legs and gaining long mouthparts. Once they settle to feed, this pest is no longer capable of moving about on the host. Female scales remain on the bark of twigs, while male scales settle on the needles. The males are much smaller and the winged adults are generally unnoticed.
Figure 3. Female striped pine scales. Courtesy of Brian Schildt, PDA
Figure 4. Scale crawlers moving over the top of a female scale. Courtesy of Rayanne D. Lehman, PDA
Monitoring and Management Strategies
- Plant trees with adequate spacing between them to prevent crawlers from moving tree to tree on overlapping branches.
- Inspect seedling stock before planting for presence of scales on the young growth.
- Scout fields of susceptible trees for presence of scales on last season’s growth. Pay particular attention to trees attractive to ants and stinging insects.
- If only a few trees show severe infestation, remove these trees from the field before bud break and burn or chip them.
- Monitor known scale infestation for presence of emerging scale nymphs.
- Growing degree days: Crawlers emerge at 400–500 GDDs.
- Avoid mowing during crawler emergence to prevent mechanical spread.
- At the end of the season, evaluate results and update records.
- Encourage naturally occurring parasitoids and predators. Lacewing larvae and lady beetles feed on crawlers.
- Do not use a broad-spectrum insecticide that will kill beneficial insects.
- Remove and burn or destroy severely infested trees before bud break.
- No recommendations are available at this time.
- Apply dormant oil in fall or in spring before bud break.
— Only apply oil when temperatures are above freezing.
— Oil will remove “bloom,” or blue color, from blue specimens.
- A single insecticide treatment applied at crawler emergence in early summer is generally effective. After first spray, inspect foliage with a hand lens to determine if the spray was effective or if a second spray is necessary.
- Purchase and plant scale-free nursery stock from a reputable company.