from the employee owners at Gardener's Supply Co.

Spinosad: a New Option for Control of Lily Leaf Beetles

Products with spinosad offer one more control option for lily leaf beetles.

Flower gardeners are a peaceful lot—at least until someone comes between them and their favorite blooms. Then, they get mean. At least some of us do.

It was about three years ago that I first heard whisperings in the halls at Gardener’s Supply of a new pest: “Something is destroying my Oriental lilies! What can I do?” The unspoken reply: “How far are you willing to go to save your lilies? Will you use chemicals?”

The culprit, the lily-destroyer, the evil insect is Lilioceris lilii, aka: The Lily Leaf Beetle. Oh, these scarlet beauties are striking in the garden. But then they breed and their disgusting offspring take over, devouring the lilies and covering themselves in their own poo.

The devastation brings out bloodlust in some gardeners—even the earth-friendly ones. At first, I tried neem, a relatively harmless spray that does wonders on aphids and controls blackspot on roses. It worked to control the larvae the first year, but I had to spray frequently (every 10 to 15 days). The second year, I couldn’t keep the larvae under control. My lily crop was hit hard, and I got few blooms. Last year, I decided to resort to a systemic called imidacloprid. The results were instantaneous and effective. No more poo-covered larvae; no more devastation.

Larvae of the lily leaf beetle

The eggs of the lily leaf beetle are usually found on the underside of the leaves, as shown on this fritillaria. They’re smaller than poppy seeds, and usually bright red. If you see these, you’ve got a problem.

Still, imidacloprid is not something I can feel good about. Systemic insecticides are harsh. Plus, studies have shown that imidacloprid can be harmful to bees, so I’m giving it up. I need a new approach.

I’ve been reading about something new, a substance called spinosad, which is made from a soil-dwelling bacterium, Saccharopolyspora spinosa. The sprays are said to control foliage-feeding caterpillars, beetles, borers and other pests. When used carefully (read the label!), it’s not supposed to effect beneficial insects. Plus, spinosad has been classified as an organic substance by the USDA National Organics Standards Board. This year, I plan to try Monterey Garden Insect Spray, which is one of the formulations. I’ll let you know how it goes. Have you seen lily beetles in your area? Let me know what works for you by posting a comment, below. Already I’ve had reports from two customers: one infestation on fritillaria and another on Asiatic lilies. Both sites were treated with spinosad.

In the meantime, keep your fingers crossed that researchers will find something that can be used to keep these pests in check. According to David Sims of the North American Lily Society, there is concern that the beetle will wipe out native lily populations. The group has been a sponsor of a study at the University of Rhode Island, where researchers are using predatory wasps to control the beetle. So far, the results have been encouraging.

-David Grist, Online Content Coordinator

5 Comments

  1. Bobo
    June 4, 2008    

    A word of caution… Spinosad IS very toxic to bees, particularly just after applying!

  2. June 4, 2008    

    As with most pest controls, spinosad should not be applied when bees are active.

    According to the EPA’s definition, spinosad is toxic to bees, but only when it’s wet
    However, when it dries, the effect on bees is negligible. Here’s what I found: “The topical acute activity of spinosad against honeybees is less than 1 µg per bee which places spinosad in the highly toxic to bees category of the EPA. However, once residues have dried completely, toxicity of foraging bees is considered negligible (Mayer and Lunden, 1998).”

    For more information, visit the University of Minnesota’s IPM World Textbook:

    http://ipmworld.umn.edu/chapters/hutchins2.htm

  3. Anonymous
    August 20, 2009    

    Minimize your effect on our already-stressed bee population by keeping a bee journal.

    Spend a fortnight observing the activity of your area’s colonies, logging daily the time of first appearance, peak activity, and end of interest in your lillies. Note whether they come back to your lillies after moving on to other flowers, and whether any drift in their daily timing might require further observation of their routines in order to determine a safe dosing time for your spinosad-containing product.

    Apply product at least three hours before the first shift of honeybees clocks in.

  4. KO
    May 22, 2010    

    Thank you for your wonderful Blog! I have those disgusting red, screw and live in your own poop, beatles! I LOVE the comment of keeping a bee journal and watching the bee “shifts.” I’ll do that first then spray the Spinsad. That is, if I can find it. Do I go to a garden place to get this?

  5. May 23, 2010    

    We offer Spinosad on our website (gardeners.com). It’s product number 38-992. Follow label instructions be mindful of the bees. Focus the spray carefully on the stem and base of the leaves, keeping well clear of the flowers.

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