Yellow Poplar Weevils
Originally posted on ecoIPM.org
I was in Northwestern Pennsylvania last week and found tulip poplar trees with leaves that had brown dried edges and small brown spots. From a distance the trees looked like that had leaf scorch or some disease. It turned out they were covered in small black to blue weevils call yellow poplar weevils, Odontopus calceatus. I have never encountered these in Raleigh. The authoritative Insects that Feed on Trees and Shrubs by Johnson and Lyon has a short entry on this critter. Apparently theoverall distribution is from New England south to Louisiana but are most common in central Appalachia. This fits with the location of the trees I found and with reports from Cliff Ruth that these are common in the mountains of NC this year.
A quick google search turns up dozens of news articles from PA and WV describing outbreak populations and damage this year.
There is one generation per year. Adults overwinter in leaf litter fly to trees in spring and lay eggs in early summer. A report from Auburn describes the life cycle in the South. Larvae and adults feed on leaves causing blotch mines and holes. They pupate within leaf mines. New adults emerge in mid-summer, feed a little, then become scarce until the following year.
These probably do not threaten tree longevity or growth especially if they just turn up occasionally. They will make your tree look a little ragged though. Since there is one generation per year if you could dislodge or kill the bulk of them with horticultural oil or soap you would reduce the damage. A pyrethroid would also kill adults but maybe not all the larvae in mines. Other beetle-active systemic products like neonics or Acelepryn should kill the beetles and larvae but it may be late in the year to try and make drench applications you could try a foliar application.