The emerald ash borer (Agrilus planipennis) is a green jewel beetle
native to north-eastern Asia that feeds on ash species. Females lay eggs
in bark crevices on ash trees, and larvae feed underneath the bark.
It is an invasive species and is highly destructive to ash trees native
to North America.
By 2019, the ash borer was destroying most of the ash population in Pennsylvania. The primary cause appears to be due to climate change and the warmer winters. After 400–500 accumulated degree-days above 50 °F, adults begin to emerge from trees in late spring, and peak emergence occurs around 1000 degree-days.
The beetles also appear to be taking advantage of weakened tree health attributed to ozone, acid rain and moisture.
The following pictures are from Blue Mountain, Pennsylvania in the summer of 2019.
