Five years ago, my sister in central Massachusetts complained that red beetles had eaten all of her Stargazer oriental lilies. The next year a friend and fellow gardener in Riverside mentioned that she lost her orientals to red beetles. The year after, the infestation reached my Barrington lilies.
The red lily leaf beetle (Lilioceris lilii) has been spreading through New England since the early 1990s. It's a European import and it has no natural predators in the United States. And in a matter of weeks, lily beetles can completely defoliate your lily garden. Three years of repeat infestation have destroyed most of my Asiatic and Oriental lilies.
But I'm not ready to throw in the towel. Armed with education and Neem oil, I'm prepared to do battle. Here's what I've learned.
The adult beetle is about the size of a lady bug, but a little more oval in shape. It's bright red and has black legs, head, antennae and belly. Their reddish-orange eggs hatch into larvae that look like slugs. These larvae attach themselves to the underside of leaves and cover themselves with a disgusting fecal shield. Larvae hatch into bright orange pupae, which drop to the soil.
The adult beetles dig into the soil in late summer and emerge in early spring. These beetles feed on the young lilies and look for mates. After mating, female lays eggs on the underside of leaves.
The main damage to the plants is done by the larvae, which hatch in 7-10 days. They feed for 2 to 3 weeks, then drop into the soil and begin to pupate. The next generation of beetles will emerge in another 2 to 3 weeks, and the cycle begins again. This takes place several times from early spring to summer.
There is no easy way to get rid of lily beetles. If you have only a few lilies, you can try hand-picking. First, remove the adult beetles. They're not easy to kill, so even if you squish them you'll want to drop them in a pail of water to which you've added soap or vegetable oil. The additive is important. They'll crawl right out of plain water, so don't waste your time and theirs.
Bear in mind that these are tricky little buggers. If you try to grab one and miss, they'll fall to the ground and lie on their backs. Since their undersides are black, this renders them almost invisible. Putting a light-colored cloth or a white garbage bag under the lilies before you start picking will go a long way toward foiling escape attempts.
The next step is wiping down the underside of the leaves. Look for lines of orange dots -- those will be the eggs. Be sure to remove any disgusting clump of brown sludge you find. That's the larvae. Hand-picking is effective if you keep at it every day, but even two or three rainy (or busy) days is enough for beetles to do serious damage. So you may want to combine hand-picking with another solution.
Some gardening websites recommend spraying your lilies with a soap solution. I've tried this. The result is very clean beetles.
The best choice for organic gardeners would be Neem oil. A solution of Neem will repel beetles and it kills larvae. It must be applied every 5 to 7 days after the eggs hatch.
Systemic insecticides that can be applied to the soil now. If you're more concerned about your lilies than the long-term effect of pesticides, check with gardening centers for products.
There is one bright spot in this scenario. Lily beetles only eat true lilies and fritillaria. They don't bother day lilies.
If you aren't sure lily beetles have found your garden, take a trowel and dig no more than a half inch. Beetles live near the surface of the soil. If you've got them, it won't take long to turn them up.
Please note that these beetles are emerging. Yesterday I checked one of my emerging Asiatic lilies and found an adult beetle just under the soil. The lily sprouts already show some leaf damage from the emerging beetles. If you're got lily beetles in your garden, now's the time to prepare a solution of Neem oil and start spraying.