by Connie Oswald Stofko
Margaret Raupp, coordinator of Open Gardens, alerted me to a couple of problems with disease and pests that she noticed while touring the gardens.
We’ll talk about the first one, lily leaf beetle, today.
Raupp said that when she visited an Open Garden in Lockport, the garden of John Taylor and Mary Brennan-Taylor, almost all of the Asiatic and Oriental lilies were lost to the lily leaf beetle, an invasive species that’s fairly new to Western New York. After she visited that garden, Raupp found it in several other gardens where the gardeners didn’t even know they had it.
I checked with John Farfaglia, extension educator with Cornell Cooperative Extension in Niagara County, who said he started getting calls about this bright red bug last year.
“In some cases, it does a pretty good job chewing leaves,” he said, “and some people report that the flower buds were chewed, too. Just a few beetles can do a lot of damage.”
These insects are a problem for true lilies that grow from a bulb. They also attack fritillaria, a spring bulb that some gardeners like.
The bugs aren’t a problem for daylilies, which aren’t true lilies and grow from a tuber.
If you had lily leaf beetles this year, expect to have them next year, Farfaglia said. If you didn’t have them, look for them in early spring.
The bug is large enough that you will be able to see it, and it’s bright red with black legs, so this is a problem that’s fairly easy to diagnose.
According to a Cornell University factsheet, both the larvae and adults feed on the leaves and flower buds. This doesn’t kill the plant, but it ruins the flower, and of course, who wants to grow lilies if you don’t get the pretty flower?
There are two things you can try to get rid of the lily leaf beetle. One is picking them off by hand, which is hard to do, and the second is using a pesticide, which you can’t do until next spring.
It’s hard to pick off the adults because they move so fast, and the “larvae are disgusting and difficult to hand pick,” according to the fact sheet. If you want to try to get rid of the adults by hand, the sheet recommends holding a jar of soapy water underneath the branch that has beetles. The beetles tend to drop from the branches when disturbed, so your goal is to catch them in the soapy water as they drop. Wait a few hours before dumping out the soapy water to make sure they have completely drowned.
If you want to go the pesticide route, don’t try it now, Farfaglia said. You have to catch the insect in the early stages before the damage is done.
“If you catch them early, one treatment with pesticide at the right time should head them off,” he said.
The larvae hatch in late May to early June. That is the most destructive stage.
Because the lily leaf beetle is rather new to the state, few pesticides are registered for use, according to the factsheet, but it lists some pesticides that could be used.
Do not use insecticides on plants with open flowers; you don’t want to kill bees and other pollinators. This is another reason not to apply pesticide now.
The factsheet adds this lake-friendly tip: Choose the right plant for the right place. Since these beetles attack only lilies that grow from bulbs and fritillaria, consider replacing your lilies with other perennials that aren’t affected.