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Prevent Red or Scarlet Lily Beetles (Lilioceris lilii) from Destroying Plants

Scarlet lily beetle

Lilies are the third most imported Dutch bulb in the United States and serve as an important perennial plant. Since the accidental introduction of the scarlet lily leaf beetle to the country in 1943, it has spread as an invasive species with increasing sightings in different states since 2014.

The lily leaf beetle (LLB) (Lilioceris lilii), also known as the scarlet lily beetle, is an invasive insect of Eurasian origin. The adults are between a quarter to three-eighths of an inch long, bright scarlet-red, with black legs, head, and antennae. Larvae are yellow, orange, or brown.

In Eurasia, where lily leaf beetles (LLB) are native, parasitic wasps control populations. These wasps are under review for introduction into the USA, but in the meantime, you need some solutions. I share what has worked for me in this article, adding some context to this flaming feeder’s life cycle and habits.

Table of Contents

    Introduction to the Scarlet Lily Leaf Beetle

    The scarlet lily leaf beetle was unintentionally imported into North America via Montreal, Quebec, in 1943. It was found in Massachusetts during the summer of 1992, causing havoc in flower beds everywhere it went.

    In Wisconsin, it was first detected in 2014 and seven years later had been seen in 21 counties. Nine out of the ten Canadian provinces and 14 states in the United States, including the New England states, Pennsylvania, Minnesota, and Washington, have reported the presence of LLB.

    Given the native distribution of LLB and the suitability of its environment, it is probably capable of spreading too much in the United States, and everywhere where the Liliaceae family grows.

    The Beetles Life Cycle

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    Lily Leaf Beetle Eggs

    The lily beetle is known to lay its eggs and develop only on true lilies (Lilium species), fritillaria (Fritillaria species), and other members of the family Liliaceae.

    Usually, early in May, adult beetles start laying eggs on the undersides of lily leaves. The eggs are elliptical and placed in rows resembling tan lines, and the eggs will become orange before changing to a deep crimson color just before they hatch. The larva will emerge at around 72 °F (22 °C) in a week.

    Lily Leaf Beetle Larvae

    The larvae are slug-like in appearance, with soft, plump orange, brown, yellowish, or even greenish bodies and black heads.

    The young larvae initially feed on the undersides of the foliage but eventually will move to the upper surfaces and the buds.

    While they feed, the larvae pile their excrement on their backs, making them objectionable to hand-pick backs, and this forms a barrier of sorts against pesticides.

    The larval feeding is the most destructive and lasts two to three weeks. The larvae then drop into the soil to pupate.

    Fun Fact: There are more than 100 species, of which 80 of them occupy Asia

    Tony O’Neill

    Scarlet Lily Beetle Pupa

    After 16-24 days, the larvae will drop into the soil to pupate. The pupae are florescent orange. New adults emerge in 16-22 days, feeding until fall. This generation will not mate or lay eggs but overwinter in the soil or plant debris.

    Lily Leaf Beetle Adult

    The adult LLB will spend the winter underground and come out to eat from late March to June. The adults like damp, cold, sheltered, shaded settings.

    Usually, in May, the adult beetles will lay their eggs on the undersides of the lily leaves in clusters of around 12. Throughout two growing seasons, the female beetle will lay 450 eggs.

    All sections of the plant that are above ground are attacked by both the larvae and adults, who can completely defoliate a plant, causing it to lose its vitality.

    Damage to the foliage and blooms may weaken the plant and make it more vulnerable to ailments like lily grey mold (Botrytis elliptica).

    Monitoring Lily Plants For Eggs

    Watch adults, larvae, eggs, and feeding damage throughout the growing season on possible host plants. Beginning in the spring, when lilies and fritillaries appear, inspect plants for adult LLBs and their eggs on the underside of leaves. In midsummer, look for larvae that are covered in frass.

    While pests like the Japanese beetle don’t appear until well into summer, the lily leaf beetle can be a threat throughout the growing season.

    Lily Beetle Control

    Currently, the most practical approaches for controlling LLB are to prevent them from occurring in the first place and eradicate individuals before they spread to new areas.

    Cultural Control

    Hand-picking LLB From lily Plants

    An efficient way to lessen beetle damage is by manually removing adults, larvae, and eggs. Check the underside of leaves for egg masses, especially while adults are present, and seek for beetles starting in April and continuing during the growth season, as stated in the “Monitoring” section.

    When removing the larvae from host lily plants, think about using gloves because they are covered with bug excrement.

    The larvae are the hardest to manage. Hand-picking is an alternative, but it needs frequent patrols and close attention. The larvae are difficult to squish because they are coated with feces and are slippery between your fingers.

    Put on nitrile or latex gloves. Rather than squashing them, pulling off the entire leaf and placing it in the jar is sometimes simpler.

    Choosing Resistant Plants

    The scarlet lily leaf beetle has a peculiar appetite for true lilies. Below is a table of what they will damage and what they won’t.

    Lily Leaf Beetle PreferencesMore Resistant to LLB
    True lilies (Lilium spp.)Daylilies (Hemerocallis spp.)
    Fritillaries (Fritillaria spp.)Canna lilies (Canna spp.)
    Lily of the Valley (Convallaria majalis)Calla lilies (Calla palustris)
    Solomon’s seal (Polygonatum spp.)Madame Butterfly (Lilium henryi)
    HostaUchida (Lilium specsiosum)
    Black Beauty
    Golden Joy
    Defender Pink

    [Source]

    Biological Control

    The University of Rhode Island deserves applause, especially its Biocontrol Lab. The university was heavily involved in the host range testing of scarlet red lily leaf beetle parasitoids resulting identifying four species deemed worthy of consideration for lily leaf beetle biological control in North America.

    Once the wasps lay their eggs in the red lily beetle larvae, the growing wasps use their LLB hosts as food and refuge. A wasp emerges from the corpse of its deceased host in the spring after the parasitized LLB larva has dropped to the ground to pupate.

    • Tetrastichus setifer
    • Diaparsis jucunda. Found to be the most specialized with a clear preference for the LLB.
    • Lemophagus errabundus
    • Lemophagus pulcher

    The embedded YouTube video below will give you some ideas on how to deal with the Scarlet Lily bug or beetle.

    Scarlet Lily Bug / red beetles

    According to the report: In the spring of 2021, we used an online survey to determine the status of the lily leaf beetle and its parasitoids in North America.

    We asked participants what year they had first noticed the lily leaf beetle in their gardens, what year they had experienced the worst damage caused by the beetle, and how they would describe the observed trend in damage levels (increasing, decreasing, remaining at a high level, or remaining at a low level) over the past year and over the past five years.

    We also asked them to tell us their methods to control the beetle.

    A total of 649 individuals responded to the survey. Most people (55%) who responded to the question about control methods replied that they hand-picked lily beetle scarlet from their plants. Nearly 10% reported giving up growing lilies and removing the defoliated plants from their gardens.

    Declines of lily leaf beetle in Ottawa, where we had previously collected T. setifer (Blackman, 2017), were also likely due to the activity of T. setifer. We do not have dissection results to document the establishment of T. setifer at the other 25 sites where T. setifer was released in Ontario, Quebec, Alberta, and Manitoba.

    Still, Tewksbury et al. (2017) showed that T. setifer was established at most sites where it had been released. Lilioceris lilii (LLB) populations have declined near Canadian sites where this parasitoid was released, while beetle populations have increased elsewhere in the United States and Canada.

    Chemical Control

    When used every 5 to 7 days after egg hatching, azadirachtin (neem oil) and insecticidal soaps have shown some promise in controlling LLB.

    Depending on the label instructions, systemic insecticides, such as imidacloprid, may offer efficient control as a soil drench or foliage spray.

    However, it is important to remember that imidacloprid and other insecticides should not be used on plants that are in flower or when bees are busy.

    Permethrin, cyhalothrin, deltamethrin, and pyrethrin are the active ingredients in contact insecticides that are effective against larvae.

    In general, systemic action insecticides do more harm to non-target species than shorter persistence pesticides.

    Lily Leaf Beetle

    If chemical control is required, pick less dangerous agents like insecticidal soaps and azadirachtin and use them at night or in the morning when bees are inactive.

    Neem oil (azadirachtin) is a natural pesticide derived from the neem tree. Neem repels adults and destroys larvae.

    It must be meticulously administered every five to seven days and is most effective early in the season and on immature larvae.

    Spray coverage must be high and thorough since the larvae’s “fecal shield” appears to offer some protection from sprays. Larvae in the late season appear to be slightly neem resistant.

    It is crucial to take measures while applying pesticides to save pollinating insects like bees.

    Apply pesticides in the evening, when there will be fewer bees foraging, and when there is the least amount of spray spread caused by wind and volatilization caused by heat.

    To stop drifting, avoid spraying while it’s windy. When close to blooming neighboring plants, particularly weeds, avoid spraying

    In Closing

    Whatever you choose to call it, red lily beetles may damage other plants in your gardens, such as potatoes, hollyhock, and Hosta, but the most damage will occur on true lilies and close relatives of the lily. Controlling them is a weekly exercise, manually removing them or using Neem oil.

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