Macro Monday: Scarlet Lily Leaf Beetle

I must confess that when I first discovered this beetle on one of our martagon lilies in 2015 it 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 colouration–has impressed me with its appearance since I first heard about it. However, it is a major pest of Liliaceae plants and it can be quite destructive. It was first introduced to North America from Europe in about 1943, although I had never come across them until May 2015. I captured it, photographed it and then 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 examined them and the other lilies nearby but found no more adult beetles or grubs and only two rows of eggs.

Life cycle:
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 to emerge as an adult beetle, and then make their way to the surface to begin feeding on lily plants again.

Control:
The best way to control this beetle is by hand. The larva and the frass can be pulled off the leaves with gloves and then rinsed off in soapy water. For the adults, you can try to take advantage of their defensive behaviour. When disturbed, the beetle will fall off the plant onto its back, becoming very hard to find on the soil or in the mulch. Use a small container of soapy water and hold it beneath the beetle. Reach down to pick it off. If you miss, it will, hopefully fall into the soapy water and drown. Repeat the search every two or three days.

Not to be confused with the Scarlet Malachite Beetle, below, which is harmless.

References:

More information can be found at the University of Massachusetts Extension and at Plantlilies.com.
Wallish Greenhouses also has a good control explainer.

Visit the Alberta Regional Lily Society for more information on raising lilies in Alberta.