Red Lily Beetle: A Garden Pest to Watch Out For
In the gardening world, the red lily beetle, scientifically known as Lirioceris lilli, has become a notorious pest for lily enthusiasts. This non-native invasive species, originally from Eurasia, has made its way to the UK and is now a major problem for gardeners. In this article, we will explore the ins and outs of the red lily beetle, its life cycle, and how to control this insect in your garden.
The Red Lily Beetle: An Introduction
The red lily beetle, also known as the scarlet lily beetle or lily beetle, belongs to the leaf beetle family, Chrysomelidae. They are easily recognizable due to their vibrant red colour and size. The adult beetle is around 8mm in length, with bright red wing cases and thorax, and in contrast the head and legs are black – making it a handsome looking mini-beast. Unfortunately, their beauty is deceptive; they are major pests that feed on the genera Lilium, Fritillaria and Cardiocrinum (together grouped as lilies) causing significant damage to these beautiful plants.
Life Cycle of the Red Lily Beetle
The life cycle of the red lily beetle begins in early spring when the adult beetles emerge from the soil after overwintering. They quickly start feeding on lily plants and lay their eggs on the undersides of leaves. The eggs are scarlet-orange, sausage shaped and hang in lines on the underside of the leaves. So always look under the leaves!
The larvae that hatch from these eggs feed voraciously on the leaves of lilies. The larvae will also eat the petals, seed pods, and the surface layers of the stems.
Expert tip: now is the time to check your snake’s head fritillaries and crown imperials (Fritillaria imperialis) for red lily beetle infestation. In my experience if you notice that your fritillaries are looking ragged, take a peek inside the flowers because the adults often hide inside the bells.
Lily beetle larvae are reddish brown with a black head, but they are quickly hidden under a blanket of their own black, wet-looking droppings (known as frass). This cloak of excrement probably protects and camouflages them from predators. The frass makes them appear like a bird dropping – therefore, many gardeners fail to recognise them as being the larvae of the lily beetle.
As the larvae mature, they drop to the soil to pupate and emerge as adult beetles ready to continue the cycle. The lily beetle, despite what some earlier literature may suggest, has only one generation a year.
Adult beetles overwinter in soil, leaf litter, and other messy areas both near and away from the lily plants, so it isn’t possible to treat them outside of the growing season.
Emerging overwintering adult beetles locate lily plants from volatile chemicals emitted by the leaves. Once lily beetles are active, they will attract others to the plants by producing aggregation pheromones.
Managing the Red Lily Beetle
Controlling the red lily beetle is challenging, but there are several strategies that gardeners can employ to minimize the damage caused by these pests.
Both the adult and larval stages of the lily beetle can cause damage to lily plants during their growing season (March to October). During its life cycle there is no stage where it attacks or attaches to the bulb, in other words you will not introduce lily beetles into your garden from any new lily bulbs that you buy and plant.
Some Effective Management Techniques:
Handpicking: Regularly inspect your lilies for adult beetles, larvae, and eggs. Handpick them off the plants and squash them between your fingers or drop them into a bucket of soapy water to eliminate them. The key to successfully managing this pest is to regularly check your lily plants during the growing season – this prevents the build-up of a large population of these damaging pests.
Expert tip: place sheets of newspaper under your lily plants before checking for lily beetles. Lily beetles drop to the ground at the slightest touch, and they always end upside down on the soil, where their black undersides blend in.
Avoid confusion: don’t harm the similarly looking native cardinal beetle, Pyrochroa coccinea, which causes no damage in the garden. Unlike the lily beetle, the cardinal beetle has comb-like antennae.
https://www.ukbeetles.co.uk/pyrochroa-coccinea
Last year I had a customer bring in a plastic bag containing what she claimed were squashed lily beetles she had picked off her lilies. Sadly, they were all beneficial ladybird beetles.
https://www.woodlandtrust.org.uk/blog/2021/03/ladybird-identification/
Plant resistant lily species: There is limited evidence that not all lilies are as susceptible to the ravages of the lily beetle. Research suggests that Asiatic lilies are more vulnerable to damage by the lily beetle than Oriental forms. There is also some evidence suggesting that species lilies may be more resistant to lily beetles than hybrids.
Top tip: you may read on the internet about other groups of plants being vulnerable to lily beetle damage, such as daylilies, but this is not true.
Natural predators: Encourage natural predators of the red lily beetle into your garden, such as birds and parasitic wasps, to help keep beetle populations in check.
Pesticides: Pesticide treatments are legally available in garden centres. They must be used responsibly, so always follow the instructions on the label. Plants in flower should not be sprayed because you are likely to harm visiting bees and other pollinators.
By implementing some of these management techniques, you can effectively control the red lily beetle population in your garden and protect your precious blooms from damage.
Conclusion
The red lily beetle is a troublesome garden pest that can wreak havoc on your lilies if left unchecked. By understanding the life cycle of these pests and employing effective management strategies, you can protect your plants and ensure a healthy garden. Stay vigilant, keep an eye out for these bright red beetles, and take action to keep them at bay. With the right approach, you can enjoy beautiful, healthy lilies without the threat of the red lily beetle.
So, have you had any encounters with the red lily beetle in your garden? What strategies have you used to keep these pests at bay?
Things to do:
Help the RHS monitor the spread of this pest by filling in their online lily beetle survey if you spot any of them in your garden – it only takes a couple of minutes to complete.
https://www.rhs.org.uk/biodiversity/lily-beetle
Visit RHS Wisley in Surrey to see magnificent displays of the stunning Fritillaria imperialis this weekend. You will find them growing along the paths on Battleston Hill.
https://www.rhs.org.uk/gardens/wisley
Further reading:
Slugs and snails are another major pest problem for lilies. The flower producing heads of newly emerging lilies are vulnerable to mollusc damage. To learn how to deal with these common garden pests read our blog:
https://www.capitalgardens.co.uk/blog/can-you-stop-slugs-and-snails/
