Question
English Oak
Hi Jim,
I have an English Oak approx 50 ft. tall that has developed some type of disease. Does the attached picture show a fungus or is it the result of an insect. There are some small "fruit fly" types and I spotted a small (2mm)black beetle type but don't know if they're the cause or just feeding on the fungus. Thanks for your insignt and suggestions.
John
AnswerLooks like an oak borer. The insect borers into the bark and the tree exudes sap and many other insects will feed on the sap. I would treat the area on the trunk with an insecticide called Merit or Onyx. These will be absorbed into the bark and wood and kill the insect under the bark. The sap will then stop flowing and the other insects will go away. Trees that are attacked by borers are under stress so I would also fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. Apply the fertilizer just before a rain storm and you will not need to water. This will increase the health of the tree. I would fertilize now and again in the Spring.
