Scarlet Lily Beetle
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Treat, then re-check in 5–7 days
Pick off the worst material, apply the organic option below, and look again after five to seven days. If the spread continued, escalate rather than repeating the same treatment.
Carried by insects
An insect moves it plant to plant, so controlling the carrier matters as much as treating the symptom. Check for the vector before assuming the plants infected each other directly.
Safe to compost
No pathogen carries over on this material, so it can go on an ordinary heap with the rest of the garden waste.
When and where to look
Scout the planting while temperatures hold between 10°C and 30°C.
The signs that lead here
Full problem lists for these crops
About
The scarlet lily beetle (Lilioceris lilii) is a brilliant red beetle that has spread through Europe and North America over the last few decades. Both adults and larvae eat lily and fritillary foliage, and an unwatched clump can be stripped to bare stems in a fortnight.
Symptoms
Bright red beetles, 6–8 mm long, on leaves and buds from April. Ragged holes in leaves, then whole leaves eaten away. The larvae are orange grubs that cover themselves in their own black excrement as camouflage.
Organic Treatment
Hand-picking is genuinely effective if done daily from April — check the undersides of leaves and the soil beneath, because the beetle drops and lands on its black back to hide. Squash the eggs, which are orange and laid in lines along the leaf underside.
Chemical Treatment
Contact insecticides work but must reach the larvae under their excrement shield, so thorough coverage matters more than the product. Never spray open lily flowers, which are heavily visited by pollinators.
Prevention
Inspect new lily bulbs and pots for adults, which overwinter in soil and leaf litter. Clear debris around lily beds in autumn, and check plants every few days through spring — early interception prevents the population establishing.
Crops at risk
Related problems
Scarlet Lily Beetle risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.