Key Features
- Twig and leaf browning
- Striped bumps at base of browned twig
- Honeydew and sooty mold
Symptoms
In mid-summer (July) small groups or individual leaves turn brown near branch ends. One or more bumps are present at the base of the leaf stem(petiole) of browned leaf or stem with brown leaves. Bumps have distinctive a stripe across the middle. Honeydew and sooty mold can be present on leaves and branches of heavily infested trees. Unlike a periodical cicada, affected twigs do NOT have slits cut in stems. Kermes galliformis (pin oak kermes) has been associated with a fungus that causes stem cankers and a blight that kills and browns leaves..
Biology
Oak kermes has one generation per year. They winter as immature settled scales on twigs and branches. When the weather warms in the spring (May) the scales become active and move to a new site on the stems to feed. White male scales can be seen feeding on trunk in June. Winged adult males emerge in early summer and fly to mate with females in the tree canopy. Mated females become rather large and brown with a distinctive light color stripe across the middle capable of producing over 3000 eggs from July- early September. Eggs hatch into flat crawling stages during September and October. These crawlers settle in nooks and crannies of twigs to feed before becoming dormant in the winter.
Management Recommendations
Insecticides are not very effective at controlling this pest. Apply horticultural oil when scales become active in May. This will kill immature scales and conserve natural enemies that normally keep this scale under control. Some trials show that application of a pyrethroid insecticide (bifenthrin, permethrin) could cause greater rates of mortality. Pyriproxifen, an insecticide that has proven effective against armored and soft scales may also be useful at this time.
Effective Pesticides
Active Ingredients include: Bifenthrin, Flupyradifurone, Horticultural oil (Paraffinic or superior oil) , Permethrin, Pyriproxyfen
