I must confess that spotting this beetle on one of our martagon lilies yesterday gave me a smile and added enough spring to my step that I could have managed the clicking-of-the-heels. This leaf beetle –with its scarlet and black coloration–has impressed me since I first heard about it. It is a major pest of Liliaceae plants and was first introduced to North America from Europe in about 1943. I had never come across these until yesterday when I spotted one on our martagon lilies. I captured it, and today I went out to do a more thorough search to see just how bad the infestation was. Only two Martagon lilies were showing any leaf damage. I searched them and the other lilies nearby but found no more adult beetles or grubs and only two rows of eggs.
Scarlet lily leaf beetles overwinter in the soil as adults and then emerge to feed, mate and lay eggs in spring. The slug-like larvae, which are brown, orange or yellow in color, hatch 4 to 8 days later and begin feeding underneath the lily leaves. The larvae use their own feces as a shield, and it is often this pile of frass that first draws attention to the pest because they soon begin feeding on top of the leaves. The larva feeds for about 24 days before they descend to the ground, burrowing into the soil to pupate. About 20 days later they eclose and make their way to the surface to begin feeding on lily plants again until the end of the season.
Because it does not appear to be a major infestation, I will be hand-picking to control them, but I will leave some eggs to hatch in controlled conditions so I can (hopefully) photograph the rest of the lifecycle.
According to Lynnette Westfall (in an Edmonton Hort. Society pdf) this pest was first seen in the Edmonton area in about 2009. More information can be found at the University of Massachusetts Extension and at Plantlilies.com. Visit the Alberta Regional Lily Society for more information on raising lilies in Alberta.