The lily leaf beetle is an imported pest that attacks all true lilies (not daylilies). It lays eggs only on true lilies and fritillaria species but researchers from the University of Rhode Island have found the beetles feeding on Soloman’s seal, potato, hollyhock, bittersweet and some hosta species.
The lily leaf beetle was first officially sighted in the U.S. in Cambridge, Massachusetts in 1992, most likely having arrived in a bulb shipment from Europe. They are strong fliers and can be moved to other locations on host plants, therefore they have spread rapidly throughout eastern MA and are now also prevalent in central MA.
Adult beetles have a bright red body with black legs, head, antennae and undersurface. About 1/2” long, adults squeak if disturbed to ward off predators. Larvae resemble slugs with swollen bodies and black heads. Smaller than adults, larvae cause more destruction and are repulsive in that they carry excrement on their backs.
Adults overwinter in sheltered places and emerge in the spring (late March into early April in MA) to mate. Each female lays 250-450 reddish-brown eggs that appear in irregular lines on the underside of foliage in April/May. Larvae hatch within 4-8 days. The larval feeding period is the most destructive and last 16-24 days. They then drop to soil to pupate and new adults emerge 16-22 and can be seen feeding throughout the growing season.
Adults can be removed by hand. Kill larvae and deter adults with early, repeated applications of Sevin or Bon-Neem insecticidal soap. Inspect potential host plants carefully when acquiring new ones or moving them to a new location. In May, use a liquid MERIT product such as Sevin or Bayer Tree and Shrub in the soil to kill the larvae and prevent infestation.