Pest
Lily beetle
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Watch for | Watch for in March | Watch for in April | Watch for in May | Watch for in June | Watch for in July | Watch for in August | Watch for in September |
What it is
Lily beetle is a striking leaf beetle with a glossy scarlet back and black legs and head, about 8 mm long. It was once rare in Britain but is now widespread across England and spreading north. It breeds only on lilies and fritillaries, so if you grow them, you will probably meet it.
Symptoms
Adults chew irregular holes and notches in leaves, and both adults and larvae eat flowers and buds. The larvae are orange-red, but you rarely see that colour because they cover themselves with their own black, slimy droppings, which look like blobs of wet soil on the leaves. Heavily attacked stems can be reduced to bare stalks. Rows of small orange eggs line the undersides of leaves.
Cause
Adults overwinter in soil and leaf litter, emerging as soon as lily shoots appear in early spring. Females lay eggs over a long season, and larvae feed for a couple of weeks before dropping into the soil to pupate. A fresh brood of adults appears in summer and feeds until autumn.
Control
Hand-picking is the most reliable control. Approach carefully: the beetles drop to the ground and lie on their backs when disturbed, so hold a hand or a pale cloth below the leaf. Squash or wipe off eggs and larvae, wearing gloves if you prefer. Inspect every few days from March to late summer. Insecticide is a last resort, and a poor one because of the risk to bees visiting lily flowers; follow the label if you must.
Prevention
Grow lilies in pots where you can see them easily, ideally at eye height on a table. Check new bulbs and plants before adding them to the garden. Clear fallen leaves from around lilies in winter to reduce overwintering sites, and keep watch for beetles on nearby fritillaries.
Plants often affected
Could it be something else?
These problems share some of the same symptoms. Compare them, or run the symptom checker with these signs ticked.
Months to keep an eye out: March, April, May, June, July, August and September.
Sources
Identification and life-cycle details were checked against the references below. Text and advice are our own. See our editorial policy.