Plant Diseases/egg sac?

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QUESTION: This morning I found 3 (maybe more) pinkish, waxy, ball-like, egg sacs on my maple tree leaves.  The balls are 1cm in diameter.  I haven't cut one open yet, but holding it up to the light, the dark spot (what ever organism is in it) looks to be about 4 to 5mm.  I've Googled every description I can think of and can't find anything.  Any ideas?

ANSWER: Monica:

If possible, you are welcome to send me a closeup photo of this structure for an identification.  There are several "gall" insects that can produce such a structure.  Chemical control is usually not necessary since these insects usually don't have a significant impact on the overall health of the tree.  There are many natural predators that keep these things in check.  Another option to consider- collect a few affected leaves and carry to your local garden center- many times these folks may have seen such insects and can offer an id.  Simply raking up the leaves during the winter is usually enough to manage these types of insects since they can spend the winter on the fallen leaves.

Regards
Steve

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QUESTION: Thank you.  Here are two pix.

Answer
Hi Monica:
Thanks for your pictures. I contacted my entomologist colleague and he says it is an insect gall.  There are numerous types of galls that can occur on tree leaves.  These structures will usually contain a single egg that will develop into a mature insect.  (There is a cherry oak gall that looks similar).  This gall is likely caused by a tiny cynipid gall wasp (many species!)that is in the 1/4 inch size range. As mentioned in my earlier note, chemical management isn't usually necessary- just rake up fallen leaves during the winter before springtime and discard or burn (if allowed in your community) or just pull off individual leaves if feasible and discard.

P.S. These leaves look very similar to oak instead of a maple.

Regards
Steve

Plant Diseases

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Dr Stephen Vann

Expertise

Plant Diseases and Disorders of Lawn Grasses, Trees, Vegetables,and Ornamentals

Experience

Plant Diseases Identification and Management

Education/Credentials
B.S. Botany --- Miss. State Univ. M.S. Plant Pathology --- Miss. State Univ. Ph.D. Plant Pathology --- Texas A & M Univ.

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