Keep an Eye Out for Lily Leaf Beetle
by Tawny Simisky Extension Entomologist , UMass Extension Landscape , Nursery , & Urban Forestry Program . Hort Notes Vol 31:3 .
As soon as lilies break through the ground and foliage is available , bright red , overwintered adult lily leaf beetles ( Lilioceris lilii ) can be seen wandering and feeding on host plant leaves . Mating and egg laying will soon occur , and eggs can usually be found on hosts in May .
Host plants include true lilies ( Lilium spp .) and fritillaries ( Fritillaria spp .). Daylilies ( Hemerocallis spp .), however , are not hosts . Adult beetles can fly and do not necessarily overwinter right next to susceptible host plants , so they are capable of dispersing on their own to new plantings or may be carried into new areas on infested host plant material . While lilies and fritillaries are the most significantly impacted , these insects may also be seen on lily of the valley ( Convallaria majalis ), Soloman ’ s seal ( Polygonatum spp .), bittersweet ( Solanum spp .), potato ( Solanum tuberosum ), hollyhock ( Alcea spp .) and various hosta species . However , damage to these other plants is typically not significant . Lily leaf beetle is native to Europe and Asia and was first detected in the United States in Cambridge , MA in 1992 .
Mating adult lily leaf beetles . Amherst , MA . 6 / 8 / 2017 . Photo : Simisky
Now is the time to pick off and remove adult beetles from plantings where it is practical to do so . In large plantings where populations of lily leaf beetle are significant and cause great damage , other means of management may be necessary . Reduced risk insecticides containing the active ingredients neem oil or spinosad are labelled for use against leaf beetles , and may be more effective on young , still small larvae . Please note that spinosad is toxic to pollinators until the product dries ( for most , this occurs within 3 hours of application ), so do not apply these products to plants in bloom . Follow all label instructions for safety and proper use .
Lily leaf beetle eggs . Amherst , MA . Photo : Simisky
If installing new plantings in areas where lily leaf beetle has historically been a problem , the University of Maine has recently conducted studies that indicate that certain lily species limit the survival of lily leaf beetle eggs and larvae . Their researchers report that Asiatic hybrids may be the most susceptible species , while certain Oriental lilies and other hybrids may provide some resistance , including : Lilium henryi ‘ Madame Butterfly ’, Lilium speciosum ‘ Uchida ’, and Lilium ‘ Black Beauty ’.
Finally , researchers at the University of Rhode Island have identified and released parasitoid wasp biological controls that were found to be specific to Lilioceris spp . and approved by the USDA APHIS PPQ for field release . Tetrastichus setifer , Lemophagus errabundus , and Diaparsis jucunda have been a part of release , recovery , establishment , and distribution studies in New England from 1999 – 2016 . ❖
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For more information about the lily leaf beetle , visit the updated UMass Extension : Lily Leaf Beetle fact sheet https :// ag . umass . edu / landscape / fact-sheets / lily-leaf-beetle
Check out the life cycle of the lily leaf beetle showcased in Episode 2 of InsectXaminer ( short video series ).
https :// ag . umass . edu / landscape / education-events / insectxaminer
17 MLP Newsline | March 2021