Question
QUESTION: I live in Washington State, the wet eastside of it.  I have 10 Italian cypress trees.   I planted the trees three years ago and they are about 10 feet tall now, the first three years they seemed to be doing fine.  Just two weeks ago I noticed that the usually dark green needles and branches are turning a bit light.  Some of the ends of branches and needles are dying, they are brittle and yellowish and breaking off.  The very tops look ok though.  I noticed on a couple of them, on the branches near the inside they are coated with a gray like matter.  I really like these trees and would hate to loose them and suggestions?  I plan to spray with an insecticide and fungicide tomorrow.  Thank You.

ANSWER: Sounds like spider mites.  Mites are not insects but are more closely related to spiders.  They are very small and not seen easily with the naked eye. They have piercing mouthparts that they use to suck plant sap. Their feeding results in speckling (formation of tiny yellow spots) on needles. Some needles may turn brown and drop off. With heavy infestations, fine webbing may be seen on the plant. Several seasons of heavy mite feeding may kill a conifer. Although most spider mites increase in numbers during hot, dry weather, spruce spider mites are cool-weather mites. Their populations peak during spring and fall, but drop dramatically during the heat of summer when predators feed on them.

Miticides Spider mites are usually not killed by regular insecticides, so be sure to check the pesticide label to see if "miticide" is present. Pesticides claiming "for mite suppression" are usually weak miticides and will not perform well. There are few products available to the homeowner. Dicofol (=Kelthane) is registered for over-the-counter use but is difficult to find. Acephate (=Orthene), dimethoate (=Cygon), chlorpyrifos (=Dursban), diazinon, disulfoton (=Di-syston), and malathion have over-the-counter product labels but are considered weak miticides.

A newer product is Called Bayerr Advanced 3-in-1 Insect, Disease & Mite Control. It comes as a ready to use product that attached to a water hose or a concentrate that is mixed with water and sprayed in a sprayer.   

Here is a web link to more information on this product. Check with your local nursery for these products for mites.

http://www.bayeradvanced.com/product/3-in-1-Insect-Disease-and-Mite-Control/read

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QUESTION: Wow!  Thank You for the very quick reply and detailed explanation.  I'll try the 3-in-1 product and see what happens.  Any thoughts about the gray matter on some of the trees.  Looks almost like ash.  Powdery Mildew?  Can that kill the trees?  What's the best way to treat it?  Thank You.  

Answer
It sounds like the webbing from the spider mites.  During feeding
some mite species may inject toxins that cause varying degrees
of leaf discoloration and distortion. Some spider mite
species may produce webbing that covers leaves and stems when
populations are high. A simple technique for sampling, (especially conifers) is to tap a few terminals or leaves over a piece of white paper. Wait a few seconds and watch for movement. The mites may take a short time before they begin crawling on the paper.