How To Deal With Lily beetle in Your Irish Garden
What is Lily beetle?
The lily beetle is a strikingly beautiful but devastatingly destructive pest of lilies, fritillaries and other plants in the family Liliaceae. Adults are bright scarlet red, about 8mm long, with a black head, legs and underside. They emerge from the soil in spring and immediately begin feeding on lily foliage. Both adults and larvae cause severe damage, but it is the larvae that are the most destructive. Lily beetle larvae are distinctive and unpleasant — orange-red grubs that cover themselves in their own black, slimy excrement as a deterrent to predators. First recorded in Britain in the 1940s, the lily beetle has spread northward and is now well-established in parts of Ireland.
Damage Caused by Lily beetle
Lily beetle adults and larvae strip leaves, buds, flowers and seed pods from lilies and fritillaries with alarming speed. Adults eat irregular holes and notches in leaves from April onwards. The larvae, which appear from late April through summer, are even more voracious, capable of completely defoliating a lily plant within days. Repeated annual defoliation weakens bulbs, reduces flowering and can eventually kill the plant. All garden lilies and fritillaries are susceptible, though some species are attacked more heavily than others. Lily-of-the-valley, Solomon's seal and other related plants may also be damaged.
How to Prevent Lily beetle
Check lily shoots daily from March onwards as they emerge, looking for the bright red adults sitting on the foliage. Be alert to their defence behaviour — adults drop to the ground underside-up when disturbed, making them hard to spot against the soil. Plant lilies in pots where they can be monitored more easily. Avoid planting lilies in dark corners where beetles can hide. Remove plant debris in autumn where adults might overwinter.
How to Treat Lily beetle
Hand-picking is the primary control method. Check lily plants daily from early April, collecting the bright red adults and the black-slimy larvae by hand. Squash or drop them into soapy water. Adults make a distinctive squeak when picked up. Check the undersides of leaves for the orange egg strips and remove these too. For severe infestations, spray with organic pyrethrum or neem oil, ensuring coverage of leaf undersides. Chemical insecticides based on deltamethrin or acetamiprid are effective but will also harm beneficial insects.
Lily beetle in Ireland
The lily beetle arrived in Ireland relatively recently and has been spreading steadily, particularly in the eastern half of the country. Dublin, Wicklow, Wexford and Cork gardens report the highest incidences. The mild Irish climate has allowed populations to establish readily, and the beetle continues to spread westward and northward. Gardeners in western Ireland may not yet have encountered lily beetle, but it is likely to arrive in coming years. Irish lily growers are advised to be vigilant from March onwards. The RHS and Irish Garden Plant Society track lily beetle sightings to monitor its spread.
Plants Affected by Lily beetle
Treatment Products at MCDS.ie
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