Expert: Jim Hyland - 8/6/2006

Question
We live in MD, and have a Blue Spruce about 7 feet tall.  It has clumps of brown pine cone shaped things hanging all over--they look likw dead pine needles mixed with spider webs--they are attached by what apprears to be a web or something bug related.  Are you familiar with this?

Answer
These are Spruce spider mites. Mite feeding can cause premature loss of needles leading to twig and branch death. Heavy infestations can kill trees, especially during drought periods.
Attacked needles appear mottled and often turn yellow to brown.

Mites produce abundant silk that collects dust, dead needles, etc. This imparts a gray appearance to trees. Examination with a hand lens should reveal webbing and shed skins.

Avoid growing spruce on nutrient poor, drought prone soils.
Water spruce trees heavily during periods of drought.

Chemical: Insecticidal soaps can be useful products though they often require multiple applications. Miticides are preferred over general insecticides. The insecticides are more likely to destroy the natural enemy complex of spider mites. Mid-summer applications should be avoided since this mite reduces activity during the hottest parts of the summer.
A couple of these are Dicofol and Dimethoate. Check with your local nursery/ garden type store for these. Spray the foliage completely and it may take a couple of spray application to control the mites.