This maple leaf seems covered with Nerds candy. A quick taste reveals the bumps in question are anything but sweet. What in the woods is it?
Answer
The marks on this leaf were caused by maple gall mites. Picture them as tiny spiders. The abscesses on the leaf – called bladder galls – are green at first, before turning red and black. Sometimes there are so many galls on one leaf that nearly the entire surface is covered.
Bladder galls form when adult mites start feeding in early spring. The mites munch on newly-forming leaves, and as the leaves grow, leaf tissue grows out and forms a gall around each mite. The gall help protect the mites from predators.
Once a leaf is full size, each mite lays eggs and dies. Eggs hatch quickly, with hundreds of tiny nymphs inside each bladder gall. Nymphs are carrot-shaped and worm-like. They are whitish-orange with two pairs of legs.
Once the nymphs have grown into adults, they leave their gall and crawl to new leaves. The cycle continues until late summer when the tree stops new leaf growth for the year. These parasites cause very little damage to the tree.
The information here was taken from the Northern Virginia Ecology website.
Photo courtesy Ronald S. Kelley, VTDFPR.
This week’s contest winner was Brendan Chrabuk of Morrisville State College