ForesTree - A Guide to Tree Health

Pest and Disease Information

Blue Oak
  • Quercus douglasii - Resistant to Verticillium. Susceptible to Caterpillars, Insect Galls, California Oak Moth, Gall Wasp and Scales, Crown Rot, Mistletoe, Oak Root Rot, Brown Rot, Powdery Mildew and Root Rot. Additional and expanded information listed below.

  • For further tree information:
       SelecTree (1234) | Silvics of North America
9 Records Found
Disease or Pest NameDescription of Disease or Pest

Brown cubical rot
Laetiporus sulphureus

Laetiporus_sulphureusThe fruiting bodies of brown cubical rot are annual. They are spongy to leathery and up to 40 cm wide. They may appear as bracket-like or occasionally they are stalked. Fruiting bodies may occur in larg...

Oak root fungus
Armillaria mellea

Armillaria_melleaArmillaria cases reduced terminal growth and general decline in affected plants, As the Armillaria advances dieback of twigs and branches (most apparent in hardwoods) can occur. Crown symptoms include chl...

Phytophthora root disease
Phytophthora cinnamomi

Phytophthora_cinnamomiP. cinnamomi causes a general plant decline. Plants can be killed quickly causing them to retain dead leaves for a long period. Plant symptoms include leaf and twig dieback, bleeding through bark cracks,...

Powdery Mildew
Microsphaera alni

Powdery mildew may occur on any green plant tissue or on flowers and fruits. Light colored mats of fungal growth often appear on infected leaves. Infected leaves may drop prematurely and leaves and shoot...

True Mistletoe
Phoradendron villosum

phoradendron_villosumTrue mistletoe is an evergreen parasitic plant with developed stems and leaves. The infection causes swollen branches and brooming. Most infections start in the upper crown of the tree, since the plant i...

California oakworm
Phryganidia californica

phryganidia_californicaCalifornia oakworm is an important defoliating pest of ornamental coast live oak. Most years it is of little concern, but some years the damage is extensive. California oakworm seldom kills trees, but it...

Fruittree leafroller
Archips argyrospila

moth"Fruittree leafroller can be a serious pest throughout California. It occurs on a very large number of ornamental trees and is particularly damaging to deciduous and live oaks. Even if completely defoliate...

Gall wasp

Cynipidae_gallHundreds of species of gall wasps occur in the oaks in California. The female wasp deposits her egg in the plant tissue and the plant produces the gall around the developing wasp. They generally do not d...

Oak pit scales
Asterolecanium minus

Asterolecanium_minusOak pit scales feed on oak twigs causing ring-shaped depressions on the bark. Death of twigs and distorted terminal growth may result from heavy infestations. Mature scales appear as brown, gold, or gree...