Question
My maple tree, which is maybe 6 years old has "eggs" all over the leaves. It had them last year also but when I pop or open them, nothing is in it...It seems to be part of the tree. Is the tree fighting something and it shows up as bumps on the leaves? Is there something I can use to heal it?

Answer
Sounds like leaf galls. Galls are irregular plant growths which are stimulated by the interaction between plant hormones and growth-regulating chemicals produced by some insects and mites. The maker receives food and protection from the gall tissue. Gall populations fluctuate from year to year, occasionally becoming very abundant. Despite the aesthetic impact and premature leaf drop during outbreaks, tree vigor is not affected significantly.



Gall makers must attack at a particular time in the year to be successful. Otherwise, they may not be able to stimulate gall production. Generally, initiation of leaf galls occurs around "bud break" or as new leaves begin to unfold in the spring. Once the symptom or gall appears, the organism is protected in the structure, making remedial actions ineffective.

Most galls occur on early spring foliage that develops near the trunk and on larger branches. Additional galls are formed on newly developing leaves later in the summer but mites are most active early in the season. Galls usually form on a small proportion of the leaves and tree health is unaffected.

Treatment is usually not recommended since they cause little real damage to the tree except aesthetics. Here is a web link to pictures and information on insect galls and treatment IF you want to do this.

http://ohioline.osu.edu/hyg-fact/2000/2004.html