Eggs are laid on the surface of the bark, in bark cracks and crevices or just under the outer bark of ash trees. The eggs, which are very small and reddish-brown, may be laid in groups or individually.
Emerald ash borer egg group
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Eggs hatch in 2-3 weeks and the larvae immediately begin chewing through the outer bark to the phloem. Larvae begin feeding in late July, but most feeding and growth occur from August to October. Larvae feed in S-shaped tunnels, called galleries, in the phloem. As the larva feeds and grows, the galleries get larger. The galleries disrupt the transport of nutrients and water within the tree.
Emerald ash borer galleries in ash tree phloem
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Most larvae overwinter as prepupae in cells found about a half-inch into the sapwood or outer bark.
Emerald ash borer prepupae
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