Question
Hi,

I went out to water my young (<10 yr old) Oak Tree and I was shocked to see 100"s of black beetles no bigger than 0.5 - 1.0 cm climbing all over the lower bark and around the tree.

Are these harmful to my tree and if so, how do I get rid of them?  

Thank you in advance!

sincerely,
Jennifer

Answer
Hi Jennifer,

Without seeing the beetles, I cannot tell you what they are.  Check your tree for evidence of damage such as chewing holes on the leaves or boring damage (sawdust, holes) in the trunk. I think that given the number of beetles, that they "hatched" in the area and climbed the tree.

If you suspect that the beetles are causing damage or if you want to get rid of them just in case, you can use an insecticide.  You can spray them with a product such as insecticidal soap or Sevin, both of which can be bought at your local garden center.  You can also make your own insecticidal soap by searching on the internet for "homemade insecticidal soap."  Depending on the site, they will give you different amounts of dishsoap and water.  Some may add vegetable oil, pepper, garlic, etc. to the solution.  If you only treat the trunk, you should be safe with any of the solutions.  If you use something containing oil, you may want to come back and wash the trunk the next day since the oil can get a rancid odor.  If you need to treat the leaves, it is best to spray only a few leaves and wait a few days.  If any brown or rusty spots develop or if the leaves fall off, then the solution is likely to be damaging the tree and shouldn't be used on leaves.  If the leaves look normal after a few days, then you can treat the leaves if necessary.

Good luck!