Beetles taking toll on local lily plants

PHOTOGRAPHER: Peter R. Barber

Lily Beetle damage on plants in the garden of Phyllis Ochs of 229 Seward Place in Schenectady Tuesday.

Oriental lilies were traditionally some of the easiest plants to care for in Phyllis Ochs’ garden — up until last year, that is.

One June day in 2012, the Schenectady resident went out to admire her flower garden and noticed that the leaves on her lily plants had been eaten away.

She peered at the underside of one of the leaves that had been chewed ragged and discovered “all sorts of crud.”

That crud, she learned, was the feces-covered larvae of the lily leaf beetle, a pest that is attacking lily plants in a growing number of local gardens.

The bright red beetle, which sports a black head and underside as well as black antennae and legs, has a taste for true lilies — those belonging to the genus Lilium.

That group includes Asiatic, Oriental, Easter, tiger and Turk’s cap varieties, which are all grown from bulbs. Common daylilies are not at risk.

Female lily leaf beetles can lay up to 400 bright red eggs on the underside of leaves, and larvae hatch out in about five or six days, according to Scott Kirkton, an associate professor of biology at Union College.

The larvae are what do the bulk of the damage to the plant.

“There’ll be a row of 8 or 10 of them working their way from the tip [of the leaf] down to the plant,” explained Timothy McCabe, New York’s state entomologist. “They’ll completely strip all the green off the plant.”

To deter predators, the larvae, which are between 6 and 8 millimeters in length, carry a shield of excrement on their backs.

The beetle is believed to have been shipped from Europe along with ornamental lily bulbs and has been present in Montreal since the mid-1940s.

The beetle first showed up in the U.S. in Cambridge, Mass., in 1992 and was first discovered in New York in 2009 near Rochester, said Kirkton.

About a month ago, Kirkton discovered the beetles for the first time on the sole lily plant in his yard in Old Niskayuna.

He picked them off and hasn’t seen any since, but the damage had already been done.

“Our lily doesn’t even look like a lily anymore, so they may have moved on to something more tasty,” he speculated.

The beetles are moving into more gardens locally.

While helping a neighbor in her garden recently, Ochs discovered the beetles there, and other friends on Upper Union Street and in Scotia are having issues with them this season as well, she said.

If an infestation is left unchecked, the insect can kill the plant, Kirkton cautioned.

Control of the beetles can be a challenge, since the adults overwinter in the soil and they are strong flyers.

They emerge in the spring and start laying eggs on lily leaves in May. After the eggs hatch, the larvae feed, then drop down to the ground where they pupate and emerge as adults.

Once the beetles sense the presence of danger, they drop off the lily leaves and turn on their backs when they hit the ground so their black underside is showing, making them difficult to spot. When they are picked up, they make a squeaking sound, another defense mechanism.

Holding a bowl of soapy water beneath the lily’s leaves before disturbing the beetles is the best way to eliminate them, said McCabe. When the beetles drop from the leaves, they will drown in the soapy solution.

Larvae removal requires a more labor-intensive approach.

“The larvae will kind of hunker down, so you’ll have to put on your latex gloves and run the leaves between your fingers and get the larvae off and let them drop down into the soapy water, too,” McCabe said. “So that means several visits all summer long to your lily plants to keep them beetle-free.”

Eggs can be removed in a similar manner.

Pesticides can also be used to control the beetle, but they kill beneficial insects, too, cautioned Jason Dombroskie, collection manger for the Cornell University Insect Collection and the coordinator for the college’s insect diagnostic lab.

Infestations can also be staved off with good prevention practices.

Purchase lily plants from a reputable garden supplier, suggested Dombroskie.

Since the beetles overwinter in the soil, if lily plants are shared from garden to garden, the pest can be transported to a new location without there ever being a sign of infestation on the plant, he noted.

A small, parasitic wasp has been introduced in New England by the U.S. Department of Agriculture as a biological control for the beetle, but its effectiveness has been limited to within a mile or so of the release zone and it’s still unknown how well the wasp will establish itself, McCabe said.

“It’s not like ladybugs that gardeners can go down to the store and get for their gardens,” Kirkton noted.

This year, Ochs was on the lookout early in the season for the bright red beetles.

“Starting in May I started killing all of the beetles I could find and then destroying the eggs under the leaves, so right now I don’t have any larvae, but my lilies are still eaten because I didn’t get out there quickly enough to stop the beetles from eating them. It’s awful,” she said.