The lily leaf beetle is a relative new comer to Northumberland gardens. It is native to Europe and North Africa and was first found in Canada in Montréal 1945. It has recently spread west and south. The lily leaf beetle looks like a bright red ladybug without spots. The head, legs and under surface are black. The adults prefer environments that are shaded, protected, cool and moist.
They are strong flyers and spread easily to neighbouring gardens.
Lily leaf beetle is a pest of lily species (Lilium sp.) and fritillary (Fritillaria sp.)
To combat lily leaf beetles it is important to understand its life cycle. The lily leaf beetle overwinters in soil and plant debris and emerges early in the spring about the same time as lilies begin to show. The adult beetles eat small holes in lily foliage. The adults mate and the female lays 250 – 350 eggs. The eggs look like a tiny string of orange dots on the underside of leaves. Some females can survive to lay eggs over 2 successive years. The eggs hatch in 5-10 days.
The newly hatched larvae feed on the underside of leaves while the mature larva feed on upper surface of the leaves. Larva is typically covered with a protective case of its own excrement and looks black, sticky and repulsive. They devour whole leaves starting at tip and proceeding to stalk. The larval stage lasts 16-24 days.
The pupal stage lasts 20-25 days and occurs in the soil with a secreted cocoon. The new adults feed until fall and do not usually mate or lay eggs until following spring.
Hand picking is most effective. Examine your plants daily and carry a small can of soapy water with you. Using a small paint brush, push the pests into the can. You can just squish adults. The adult beetles spook easily and fall to the ground black belly up making it difficult to find them. Vigilance early in season reduces damage later.
There are presently no chemicals specifically registered for lily leaf beetle control.
Neem oil will repel adults and kill larva only if it contacts them.
Home remedies include coffee grounds or citrus peels sprinkled at the base of plant. Another recommendation is to spray soil with a 10:1 water:ammonia mix as soon as lilies emerge.
A strong blast of water from a hose will dislodge larva.