Homeowners and horticulturalists alike will remember being inundated with tiny, green loopers feeding voraciously on many of our shade trees this past spring (Acer, Betula, Celtis, Fagus, Malus, Quercus, Tilia, Ulmus). These were the larvae or caterpillar stage of the Fall Cankerworm (Alsophila pometaria).
Larvae are light green with thin longitudinal white stripes down their bodies and 3 pairs of prolegs at the end of their abodomen (although, the first pair is much smaller and you might miss seeing it). Larvae grow to 2.5 cm long. There is also a black-green race. (Photo: Dave Cheung).
You could also find them hanging under the canopy, suspended on thin threads, which help keep them off the ground in case they lose their “footing”….and also so that the wind might take them to other luscious hosts. (Photo: Chris Hsia)
We had exceptionally high populations of this native pest in the Greater Hamilton area this spring, and also some little hot spots to the east and to the west. Adult fall cankerworm moths emerge starting in late October and finishing up by the end of November. So it might be a good idea to get out there and try to intercept some of the breeding adults before they lay their eggs.
Adult male moths are winged (above, Photo: William M. Ciesla, Forest Health Management International, Bugwood.org), very mobile and difficult to manage.
Flightless, adult female moths emerge from pupal cases in the soil. They crawl up the trunk, mate and lay eggs during late October-November on small twigs. This adult female moth (above) was discovered with her girlfriends on the lower trunk of black locust, silver maple and birch trees last December in the GTA (Photo: Linda Hawkins, Four Seasons Tree Care). Without wings, they look a lot smaller than the males.
Adult females lack mouth parts, they only live long enough to mate and lay eggs (what dedication). Eggs are laid on twigs in neatly organized clusters of approximately 100. (Photo: http://www.dcnr.state.pa.us). This photo is absolutely incredible!
Adult females can be trapped easily with sticky bands wrapped around tree trunks starting in late October. With the mild conditions in the fall of 2015, we saw adult cankerworms as late as December. However, this year, many climatologists are predicting that Mother Nature isn’t going to be so easy on us. And I believe them 🙂