Birch leafminer, black turpentine beetle, Colorado potato beetle, gypsy moths, fall webworm, eastern tent caterpillar……..for the last two weeks we’ve been studying bugs in my master gardener class. I’m getting a little tired of them, but since there are at least 10 million species of bugs in the world and only a small number of them are harmful, it’s important to know about the bad ones. That way you can go after them without harming the ones that are beneficial or cause no problems. I thought it would be useful to post profiles of some of the most harmful/destructive New England pests, starting with the lily leaf beetle.
Now, a pest that destroys ornamentals might not be at the top of your list of the most harmful pests. But lilies are an important part of New England’s culture and landscape–New England would look a lot different in the summer if our lilies were decimated.
Description. The bright-red lily leaf beetle, Lilioceris lilii, is a pretty little European native that turned up in eastern Mass. in 1992–probably in a shipment of lily bulbs. These little guys (and gals) love to eat the leaves of lilies and fritillaria. In fact, if they’re not controlled, they’ll defoliate and kill them. Important: They only eat true lilies, those of the Lilium genus, including Asiatic, Easter, & Oriental lilies. No need to worry about your ubiquitous daylilies–those are in the genus Hemerocallis and are not true lilies.
Lily leaf beetles lay reddish-orange eggs on the underside of lily and fritillaria leaves, and because it’s the just hatched larva that cause the most devastation, here’s a few lovely photos.
On the right is the ugly & slug-like larva. On the left the larva is carrying its frass (entymologist-speak for poop) on its back, an unpleasant habit developed to protect itself from predators (such as pissed-off New England gardeners).
Control. Because it’s a European import, there are no native predators here. University of Rhode Island researchers have traveled to Europe, picked up some larva or parasitic wasps that prey on lily leaf beetles, and are currently introducing the wasp to the region. When this introduction takes hold (and it seems to be successful so far), then hopefully gardeners will be able to breathe a little easier.
In your home garden, patrol for them and pick the adults, eggs, and larva off your lilies, making sure you destroy them–try dropping them in a can of vegetable oil or water with a lid. The adults are easy to find because of their color, but if you drop one you’ll lose it because its underside is black. So you might consider putting white cloth on the ground if you’re going beetle-hunting.
I won’t tell you not to use pesticides on them. If you suddenly find that the lilies you’ve worked hard to cultivate are being destroyed, then you gotta do what you gotta do. But try other methods first if you can. And if you do go with pesticides, ask your local cooperative extension service or master gardener group to help you choose the appropriate one.
Photo credits: Lily leaf beetle by Wikipedia; larva with frass by UMass, larva by University of Guelph.