The scales of summer
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.
Eggs of the summer generation of pine needle scale have started hatching. In most years this generation’s eggs continue to hatch over a relatively long period of two to four weeks. This extended period of hatching probably occurs because the spring generation scales develop at different rates during May and June. Some scales develop relatively quickly because they are exposed to more sun and warmer temperatures than scales that feed in shaded locations on the tree. The newly hatched crawlers move onto the expanding shoots and feed primarily on the current-year needles. The ideal window for applying insecticides to control the summer generation eggs generally occurs at around 1,500 GDD50. Spraying after nearly all eggs have hatched and most crawlers are in the hyaline stage should achieve good control.
If you are finding black sooty mold, honey dew, ants and bees on your Scotch pine you may have problems with pine tortoise scale. Growers are finding scale crawlers hatching. This scale feeds on sap on the woody shoots of pine trees. It is known as black scale because it secretes a huge amount of sticky, sugary honeydew. Black sooty mold then grows on the honeydew, turning affected shoots and foliage black.
We have found that crawlers can continue to hatch over a month. You should be scouting your trees now, looking for crawlers. The crawlers are bright pink or red, and you will be able to see them moving about on the twigs and needles. In areas where you have a heavy population, you may need to apply a second spray. Remember good spray coverage is essential.