For lily growers across much of North America, the worst threat they will face is that of the red lily leaf beetle, Lilioceris Lilli. This beetle, native to Europe, has been present in Canada and the eastern United States since 1945, but until recently was confined to the Great Lakes region.
It was initially reported 4-5 years ago around the central Manitoba town of Portage la Prairie and seemed confined to that area, but has since been sighted around the province.
Northern gardeners need to know about the lily beetle
No one can pinpoint the source of this westward progression, but it would seem that the beetles came in from the eastern part of the country either on a shipment of lily bulbs or perhaps in infested soil.
It could even have been various plants (daylilies, irises, etc.) brought in by private individuals that had their roots in soil containing larvae. No one knows for sure.
The lily beetle is actually quite beautiful. It is only 6-9 mm in length (about 1/3 of an inch). It has shiny bright red wing covers with black antennae, a head, and an underside.
The larvae are light brown and look similar to potato bug larvae. The larvae will often cover themselves with their own excrement and look like black blobs on the lily leaves; this is to discourage predators.
Characteristic holes chewed through the leaves
The beetles feed and breed only on true lilies (Lilium spp.) as well as fritillaries, and they do not attack daylilies. Adults may be found nibbling on companion plantings but major damage occurs only on lilies.
The greatest damage is done by the larvae feeding in spring, and later on by the feeding of the adult beetles. They will feed on all above-ground parts of the lily.
The lily beetle is a native of Europe and has no natural predators in North America.
Research is being done at the University of Rhode Island using parasitic wasps imported from Europe, however, they have not been approved for release in Canada. Many people prefer to catch the adults and just squish them with their fingers.
To my knowledge, no specific products have been approved in any jurisdiction for the control of the lily beetle.
The control methods that will be mentioned have been gleaned from various websites and from people’s personal experiences with control methods that have worked. Gardeners must evaluate for themselves as to what control methods they are most comfortable with.
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Life Cycle And Control Methods
It is important to understand the life cycle of the beetle in order to effectively control it. The adult beetles overwinter in the soil or under plant debris in the garden or surrounding area.
This can actually occur some distance away from your lilies. Adults prefer environments that are shaded, protected, cool and moist.
They can also be over winter near your Hemerocallis (daylilies), irises, or other perennials. Care should be taken when trading plants in a beetle-infested area so that the pest is not accidentally spread in this fashion.
The adult beetles re-emerge in early spring as soon as the lilies themselves start to emerge. They will mate, and then the female beetle will start to lay eggs on the underside of the leaves.
They lay their eggs, which are reddish-orange in color, in clusters or irregular rows. One female can lay up to 450 eggs per season.
Some control suggestions at this stage are to stir up the surrounding soil during spring cleanup and kill any beetles that turn up. Some people scratch in Rotenone dust at this time as well, but it is only effective for a few days.
You must then inspect your plants daily and handpick the emerging adults. In a very bad infestation, an alternative used by some gardeners is to spray the lilies with a general-purpose insecticide such as Sevin or Malathion.
An appropriate time should be chosen to minimize harm to beneficial insects that may be in your garden.
Beetle larvae roll themselves into their own excrement for protection
The eggs will hatch in about 7-10 days and the larvae will feed on the lower leaves for 16-24 days. They can destroy all of the top growth of your plants in a matter of days. This will severely weaken the bulbs for the next year.
As the beetles grow, they will cover themselves with their own excrement, appearing like black slugs on the leaves. At this point, you may pick off the larvae by hand or dust or spray with Rotenone.
A general-purpose pesticide can also be applied at this stage. Some people have claimed success using Neem Oil which is often sold as a leaf shine for plants.
Neem has a very short life and needs to be reapplied weekly. Regardless, any chosen method of treatment should be repeated at weekly intervals to get all of the larvae as they hatch.
Adult beetles are strong flyers, so it is possible to get a re-infestation from other gardens. It is therefore a good idea to get cooperation from your neighbors in fighting this beetle.
After the larvae finish feeding, they will enter the soil at the base of the plant and pupate for 16-22 days.
The pupae are fluorescent orange in color and are encased in rough dark-colored pupae cases. Stirring up the soil and applying rotenone or diatomaceous earth may help control emerging adults. The emerging adults will climb the plants once again and feed until fall.
They do not mate or lay eggs again until the following spring. Some adults may survive for 2 seasons. Again, this is a good time to control the beetles, which will lessen next spring’s problems.
Adult beetles are easy to spot chewing through the foliage
As the beetle becomes more established, people will come up with their own control solutions. One lady claimed that she had good success with killing the beetles by spraying them with a nicotine mixture obtained from a cigarette tea. Most people prefer to handpick their beetles.
Care must be taken as the beetles will drop to the ground at the slightest movement and are hard to find as they flip onto their backs and hide under the plants.
So do we all throw up our hands and pull out our beautiful lilies? We have learned to cope with aphids, mites, potato bugs, and many other perennial pests. That’s why I believe that if we take a neighborhood approach, with each lily grower doing their part, we can learn to co-exist with this pest.
“Down with the RED MENACE!”
Finally, as we gain knowledge in controlling the beetle in our various parts of North America, it is important that we share our successes and failures with each other.
The Manitoba Regional Lily Society has established a call-answer telephone number in Portage la Prairie. People with beetle problems can leave their name and phone number.
The number is 204-856-0844. They will then be contacted by an MRLS contact person to provide information and gather statistics. Anyone may call this number to report the beetle.
Perla Irish, who is more familiarly known as Irish, is the Content Manager at newfld.com. She loves following trends around home and garden, interior design and digital marketing. Through this blog, Irish wants to share information and help readers solve the problems they are experiencing.