What Are Lily Beetles?
The lily beetle is also known as the red lily beetle, scarlet lily beetle, and lily leaf beetle. Adults grow up to 8 mm long and have bright red bodies that are rectangular in shape with a black head, legs and underside. The larvae are soft-bodied and yellow to orange in colour with black heads, however they are usually covered in a blackish slime. Typically larvae tend to be hidden on the undersides of the leaves.
These insects overwinter as adults under debris or beneath the soil surface. In early spring, adult lily beetles will begin to surface to mate. Females will lay hundreds of bright orange eggs on the undersides of leaves, typically on plants in the Lilium or Fritillaria species. Once the eggs hatch, the larvae will feed on the host plant for approximately three weeks then pupate in the soil. Adult lily beetles will emerge less than a month later and mate shortly after. In our Alberta climate, up to three generations can hatch in a single season.
While the larvae tend to do the most damage on a host plant, adults will feed on plants as well. The lily beetle is a very destructive insect and will eat all parts of certain plants in as little as a few days. Known host plants include : lilies, fritillaria, lily of the valley, Solomon’s seal and nicotiana.
How to Manage Lily Beetles
Check Your Plants Regularly
Monitor host plants frequently during the season. Look for signs of damage due to adults and larvae. Be sure to check the undersides of leaves for both larvae and eggs. Hand-pick the adults and larvae from the plants and destroy them. Alternatively, you can spray plants with soapy water or water mixed with olive oil to remove and kill them.
Use a Control
A preferred product for control is diatomaceous earth. This dust can be sprinkled directly on the beetles to kill them. Diatomaceous earth can also be sprinkled on the dirt around the base of the host plant to help kill newly emerging adults.
Another safe way to kill lily beetles is Neem oil. Neem oil can be used to spray the entire plant to kill both larvae and adults. Be sure to repeat again in 5-7 days to kill any newly hatched larvae.