Just last week, as I peered into my tiger lily bed, a splash of red caught my eye. Even though I squashed every lily leaf beetle and larvae I found last year, some had apparently been missed and they overwintered to once more feast upon my lilies. The lily leaf beetle is native to Europe and is believed to have entered North America through plant shipments to Canada in the 1940’s. It was first confirmed in New England in 1999, when adult beetles were found in Boston. The bright red adults and rusty colored larvae have a voracious appetite for all kinds of true lilies – Asiatic, Trumpet, Tiger, Martagon, Oriental, Turk’s Cap, etc. as well as Fritillaria (Crown Imperials – although mine got a wilt and died back before the beetles came out) and our native Solomon seal (Polygonatum biflorum). Daylilies, which are not true lilies but instead in the Hemerocallis genus, are not affected. Occasionally lily leaf beetles are said to feed, but not reproduce, on hostas but this has not been a problem with the variegated ones in my gardens.
Adult, bright red lily leaf beetles overwinter in mulch and litter and emerge in the spring shortly after lilies begin to pop up and expand their foliage. The adults will feed on the leaves and flowers, mate and then females can lay more than 250 eggs on the undersides of lily leaves. The eggs will hatch in 8 days or so and then the larva will also start feeding on the leaves. To make matters worse, the larvae cover themselves with their own excrement. This is likely a defense mechanism to avoid being picked off as a menu item by birds and other predators. However, it makes squishing them unpleasant so while I will pick off beetles by hand, I admit that I use gloves for the larvae. If left to their own devices, the larvae will pupate, adults will emerge late summer and feed on any lilies left, drop to the ground to overwinter and come back to start this voracious cycle again next spring.
What’s a lily loving gardener to do??? Well, if you are a Connecticut resident join our control study!
Researchers at UConn are conducting a lily leaf beetle biological control project during the summer of 2015. If you grow lilies in Connecticut, have a minimum of 12 plants in the lily family (Oriental lilies, Asiatic lilies, Turk’s Cap lilies, or Fritillaria) in your garden, and have lily leaf beetles feeding on them, we would like your help. We will be introducing two species of beneficial parasitic wasps in June and would like to collect lily leaf beetle larvae from June through August. The parasitoid wasps attack lily leaf beetle larvae and over time these natural enemies will disperse from release sites and begin to spread through the state to reduce populations of lily leaf beetles. The wasps were first introduced in Connecticut in 2012 and have also been released in Maine, Massachusetts, New Hampshire and Rhode Island, where they are establishing and starting to impact lily leaf beetle populations. Please contact Gail Reynolds, Middlesex County Master Gardener Coordinator (email@example.com; phone 860-345-5234) if you would like to participate in the research project.
Gail wants you to know that “the parasitoid wasps are very tiny, non-social, stingless wasps and that the wasps are not a panacea that will destroy the lily leaf beetles quickly. We encourage gardeners to tolerate the beetles and the (yucky) larvae so that we can collect and inspect them. If they spray an insecticide or pick off the adults/larvae, then we can’t ascertain if the wasps are doing their thing. We could potentially have had more parasitism occurring but we can’t confirm if the larvae are removed and killed without being examined.”
Donna Ellis, UConn Senior Cooperative Extension Educator and Integrated Pest Management (IPM) Program Coordinator, who is coordinating this research project wants you to know that “The lily leaf beetle biological control project, funded in part by the U.S. Department of Agriculture, began in CT in 2012 with the release of two species of beneficial parasitoid wasps that will help reduce lily leaf beetle populations. The releases will continue this year, and Gail is looking for gardens throughout Connecticut. The releases have been made in all counties. To date, there has been one confirmed site where a parasitized lily leaf beetle larva was collected (New Haven County) in 2013. With additional numbers of beneficial wasps introduced each year in the state and the establishment of these biological control agents, we anticipate an increase in the number of parasitized lily leaf beetle larvae in the near future.”
Gail will visit potential gardens to assess the lily, and lily leaf beetle populations, and she will release the parasitoid wasps, which are reared and shipped to CT from the University of Rhode Island (URI). Gail will also be doing most of the lily leaf beetle larval collections, to ship to URI where they will be examined to determine whether they are parasitized. During the summer, Gail and Donna will receive training at URI so that we can examine the larvae at UConn.
Gail took the lead in creating a new fact sheet on lily leaf beetle biological control in Connecticut which can be found on the UConn IPM website: http://ipm.uconn.edu/documents/raw2/html/569.php?aid=569
Good gardening to you all!
Dawn (with input this week from Donna Ellis and Gail Reynolds, UConn PSLA & Extension)