Non chemical control
Where only a few lilies and fritillaries are being grown, the plants should be regularly inspected from late March onwards so that adult beetles, larvae and eggs can be removed by hand. One Lilium (Lily 'Defender Pink') is advertised as lily beetle tolerant.
For extensive infestations, it may be necessary to use an insecticide, such as thiacloprid (e.g. Bayer Provado Ultimate Bug Killer), acetamiprid (e.g. Bug Clear Ultra), deltamethrin(e.g. Bayer Sprayday Greenfly Killer, Bayer Provado Ultimate Fruit & Vegetable Bug Killer) or lambda- cyhalothrin (e.g. Westland Resolva Bug Killer). Organic gardeners can use natural pyrethrum/pyrethrins (e.g. Py Spray Garden Insect Killer, Py Bug Killer spray, Bug Clear Gun for Fruit & Veg, Pyrol Bug & Larvae Killer or Growing Success Shrub and Flower Bug Killer). These products should control newly hatched larvae but are likely to be less successful against adult beetles.
Plants in flower should not be sprayed to avoid harming bees and other pollinating insects.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)