For years Alberta gardeners were exempt from this aggressive lily pest, but over the past couple of seasons their numbers have vastly increased.
Lilioceris lilii, commonly known as the Red Lily Beetle, Lily Leaf Beetle or Crimson Lily Beetle is native to Eurasia and has most likely spread into North America from either non-inspected "bootleg" (smuggled) imports or poorly inspected bulbs and plants with soil attached. Emerging in April and May, the adult beetles lay their eggs on the undersides of leaves from about late April until early September. Eggs hatch in about a week and the larvae feed on both foliage and flowers from May through September. In two weeks, when the larvae are fully grown, they pupate underground and emerge as adults for another cycle of feeding, then return to the soil or nearby ground litter for overwintering.
Though most commonly found on lilies, the adult beetle has reported to have also been found on Hosta, Lily of the Valley and Soloman's Seal. It has been making its way westward through the Canadian provinces and now appears to be firmly established in Ontario, Manitoba, Saskatchewan, and even Calgary, Alberta, most likely due to inter-province delivery of plants with infected soil.
In spring, when lilies are beginning to emerge just a few inches out of the soil, begin looking for overwintered adult beetles, inspecting stems from all angles. Lift leaves and also carefully inspect the crowns when they are still small and before developing buds begin spreading apart. Wear disposable or dish washing gloves and put white cloth or paper under plants as you work. Hold a plastic carton of hot, soapy water under each area of the stem you are working on. If the beetles sense danger or see a shadow, they will most likely drop, dark belly side up, hopefully in the water or where you can pluck them off the light colored material. (Dropped onto mulch or soil will make it difficult to find them again, so put down your light colored mat first.)
An application of Diatomaceous Earth spread around the base of stems that might have been affected the previous summer will not only impact the adult beetles, but also help to eliminate unwary mollusks who might dine on the lily sprouts as they emerge, a double benefit. You can also lightly mist lily plants throughout summer and sprinkle the fine Diatomaceous Earth powder on the leaves. Use a puff applicator for under leaves. Our Dust Applicators are a great tool for applying Diatomaceous Earth, as well as other garden dusts such as Sulphur.
Neem Oil is a very effective control as well, both eradicating the larvae and repelling the adults. Note that Neem Oil needs to be reapplied frequently to be effective; once every 5-7 days.