Friday, June 10, 2016

What's Eating my Lilies?

Understanding the lifecycle of a garden pest is the first line of defence. Knowing how to spot lily beetle eggs, recognizing their rather disgusting looking larvae and having a simple method for eliminating the adults can go along way to having better looking lilies in your garden this summer! In her second post, Jean Godawa tackles the subject of lily beetles.

Lilioceris lilii

Like street lights, stop signs or fire trucks, the bright red colour of lily leaf beetles (Lilioceris lilii) certainly attracts our attention. The beauty of this insect, especially against a leafy green backdrop, becomes irrelevant however, as you see the damage it causes to your lilies.

Lily Beetle Eggs

After spending the winter protected from the elements, adult lily leaf beetles emerge in the spring, coinciding with the emergence of lily plants. They mate then lay orangey-brown lines of eggs on the underside of lily foliage. These pests can lay over 400 eggs in a season.

Lilioceris lilii larva

When the eggs hatch, the orange larvae feed under dark shields of their own excrement. Well protected from predators, the immature insects grow and continue to damage the plant. 

Healthy Lilies

Defoliated lily with buds intact

Several adults and larvae together can completely defoliate the lilies in your garden.

After a few weeks, the larvae drop to the soil where they pupate for a few more weeks then become adults. In the fall, this new generation will seek out shelter or burrow into the soil to overwinter. The cycle begins again in spring.

The best defence against these red nuisances is to destroy them before they have a chance to lay eggs. If you’ve been plagued by lily leaf beetles in the past, keep watch for the emerging adults as soon as your garden starts to wake up in spring.

Hand-pick the beetles off your plants and squish them between your thumb and forefinger. Don’t worry, they won’t bite, but you have to be quick. When disturbed or threatened, the beetles drop to the ground on their backs. The underside of these bright red creatures is black and blends in well with the soil.  

If the thought of squishing bugs is too unpleasant, you can drop them into a bucket of soapy water to destroy them. Where space permits, shake the plant gently over the bucket to get rid of any beetles you can’t see.

If you missed the opportunity to find the adults and there are already gooey black larvae munching away on the plants, you can hand remove those as well. Where several larvae or eggs are infesting a leaf, or if you just can’t bring yourself to squish poop-covered creatures, it might be more effective to just cut the leaf off, if the plant is otherwise healthy and robust.

Lily beetles are not originally from North America so there are no natural predators here to keep the population in check. A tiny parasitic wasp from Europe is being studied as a potential control agent for this introduced species.

We’ve been conditioned to recognize red as a warning colour. Whether by natural design or coincidence, bright red lily leaf beetles warn gardeners that their lilies are in danger.

About Jean GodawaJean is a science teacher and writer. She has been writing science-related articles for print and online publications for more than ten years. Jean holds a degree in biology and environmental science with a focus on entomology from the University of Toronto. She had conducted field research in the tropical rainforests of Asia and South America.

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  1. I have lots of lilies and have spent these last few weeks capturing and destroying Lily Beetles. Normally I find about 60 but this year only 15 so far, may be I am winning from previous years. I put a small glass under the beetle, knock it in, and then tip it onto the concrete and squash with my foot. It seems cruel but my lilies are more important to me. I don't like the eggs becoming grubs when they are covered in excrement, I watch carefully to prevent that stage.

    1. The larvae stage was something I discovered only recently. I turned over a damaged leaf and wondered what the heck I was looking at. Thank goodness Jean, who wrote this post, identified them for me.
      I swash lily beetles with my foot, but hadn't thought to capture them in a glass. I think I'll try that or perhaps a small glass bottle.

  2. I assume these beetles attack the true lilies such as Oriental and Asiatic lilies? I have lots of day lilies, but few of the other... so far I haven't seen this pest but I'll be keeping my eyes open.

    1. Thanks for commenting Kathleen. Day lilies aren't affected by this pest but, as you mention, Oriental and Asiatic lilies are common hosts. Some late-blooming Oriental species are more resistant than the Asiatics to the beetle. Check out this site for a few more details:

  3. I never knew about these, Jennifer.
    Fortunately, I don't think they've ever visited my lilies, but I sure am glad to know about them.
    Thank you so much for all of the information and beauty here.
    You have a wonderful weekend!

  4. I seem to kill so many each year. I always carry a paper tissue in my pocket, so knock the adults onto that, then stamp on them on the concrete path. I have just one lily this year which has the young on it, most of the leaves will have to come off unfortunately.

  5. There's always something to ruin the fun in the garden, isn't there? I haven't seen any of these beetles yet, but I'll be running through the garden checking for them today. Thank you for the heads up!

  6. I have to keep my eyes open for these disgusting beetles too .. I was getting wrapped up in the aphid problem .. this year seems to be one of those years for rotten garden bugs!

  7. I don't have lily beetles but a clump of lilies that are normally huge are really small this year. I have no idea why...

  8. Hi, Is this the only way - cant the plant be sprayed with something?

    1. You can spray Neem oil to kill the larvae and the bugs, but it isn't necessarily the easy fix you are hoping for. You have to make sure to get the larvae on the undersides of the leaves and you need to repeat the spray a week after the first application to make sure you have caught any eggs that might have hatched. Neem oil also has the drawback of killing beneficial insects as well as lily beetles.


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