Scout for pine tortoise scale crawlers
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
If you grow Scotch pine and had high populations of pine tortoise scale (Toumeyella parvicornis (Cockerell) last year, you should be scouting your trees for the crawlers. Particularly check trees that had black sooty mold last year. If you have trees that are within two years of harvest, you don’t want to let pine tortoise scale build up to high levels. These scales secrete huge amounts of sugary honeydew. Black sooty mold grows on the honeydew and can make the trees unacceptable to sell when scale populations are very high.
If you had some "black scale" last summer and need to apply a horticultural oil or insecticide spray, you should time the spray to coincide with this crawler stage. Crawlers begin to hatch around 400-500 GDD base 50 and continue through 1,000-1,200 GDD base 50. The crawlers are pinkish-red and can easily be seen moving about on the shoots and needles. We have found that emergence of crawlers occurs over a month long! The key to control this scale is to remove trees heavily invested, get good coverage with spray materials and continue to scout trees in June and July for crawler emergence.