PINE NEEDLE SCALE ON BLUE SPRUCE

Asked April 7, 2015, 3:15 PM EDT

HELLO! IT IS NOW APRIL AND I HAVE HAD PINE NEEDLE SCALE ON A LARGE BLUE SPRUCE FOR YEARS. WALKING PAST TJE BRANCHES AND THE NEEDLES DROP LIKE CRAZY. I LIVE AT 7364 ELEVATION IN GRAND COUNTY. CAN I SPRAY NOW AND WHAT DO YOU ADVISE USING? THANKS!!!

Grand County Colorado trees and shrubs disease issues horticulture

1 Response

Hello
I just want to be sure that you have properly diagnosed the issue -- are you seeing the white scale on the needles, or just noticing needle drop? If you have seen the scale, there are various options for control:
Pineneedle scale
Pine needle scale is more readily controlled with horticultural oils than are some other armored scales, such as oystershell scale. Oils applied during the dormant season (dormant oils) are recommended for pines. Spruce may temporarily discolor at the rates used for these treatments (about 2 percent concentration). However, we are now about out of the dormant season, so you may want to save that for next year if the following solutions don't work:

Monitor your tree carefully, and spray a "crawler spray" during the vulnerable crawler stage. Many yard and garden insecticides are labeled for this purpose, including insecticidal soaps, Sevin, Permethrin, Orthene, cyfluthrin and various oils.

Apply crawler sprays shortly after egg hatch, which can be determined by monitoring. The small, rosy-colored crawlers are detected by shaking a branch over a piece of white paper. Try this survey when crawlers are expected to first appear, from late April to late May. If egg laying and crawler activity occurs over a period of several weeks, repeat applications of insecticides, particularly if short-lived residual treatments (soaps, oils) are used.

If you miss that window, wait until all the new growth is fully expanded (it will turn the same color as the older needles), and apply a summer oil, but be aware that it can discolor spruce. Summer horticultural oil young, settled scales, as well as crawlers and eggs. Do not apply horticultural oils when new growth emerges or if plants are under stress from drought.

Summer oil and horticultural oils can be found at garden centers (or perhaps online, You might find the "crawler sprays" at hardware stores or garden centers.

Good luck!
Irene