When Magicicada cicadas deposit eggs into a tree branch sometimes the branch dies, the leaves turn brown, and the branch droops like a flag. This is called flagging.
Here are some examples of flagging from the Brood X emergence in Princeton, NJ.
Typically flagging is more impactful to trees imported to North America, but it also impacts native species. The positive aspect is it prunes weaker branches, which helps the tree, and helps other plants in the shade of the tree.
If you want to learn whether eggs/larva survive flagging read FLAGGING: HOSTS DEFENCES VERSUS OVIPOSITION STRATEGIES IN PERIODICAL CICADAS (MAGICICADA SPP., CICADIDAE, HOMOPTERA) by JoAnn White. Hint: very few survive.
A small tree with flagging:
Flagging up close:
Another small tree with flagging:
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