The pointed nail galls are caused by microscopic mites, which overwinter in the bark of lime trees and crawl on to the underside of the foliage in spring to feed. The mites secrete chemicals into the leaves causing them to produce the unusual projections into which the mites move to continue feeding during the summer. Infestations of mites and the nail galls they induce don't appear to affect the health of the trees and there's no way of controlling or preventing them.
Pointed, tubular growths appear in summer on the upper surface of lime tree leaves. These growths, or galls, may be yellowish green or red.
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