Lily Beetles Are Emerging This Month – And This Surprising Natural Trick Can Help Stop an Infestation Early
Sunflower oil is an organic alternative to using chemicals – we also recommend handpicking lily beetles as a tried-and-tested control method
Lily beetles cause headaches for all growers of these stunning plants. As spring is a key time when the adults are actively feeding and start laying eggs, gardeners should keep a close eye on their lilies this month.
Left to their devices, adult lily beetles and their larvae can cause huge damage and even stop bulbs from flowering again. Close monitoring for signs of pests and their damage means you can start controlling them more quickly. You can handpick them from the plants or spray sunflower oil to combat active pesky larvae – but it needs to be done carefully.
Whether you have them in borders or grow lilies in pots, your plants are at risk of the lily beetle. Here we reveal the signs to look for and the best methods to get rid of these unwanted pests so your lilies keep putting on a performance year after year.
All About the Lily Beetle
The lily beetle, also known as the scarlet lily beetle, red lily beetle, or lily leaf beetle, is a pest that came over from Europe and has spread across the US since the early 1990s.
The troublesome summer garden pests are small, only 6-8 mm long, with a scarlet-red body and black legs. The adults start feeding once the lilies break through the soil, typically in spring, and lay hundreds of eggs on the underside of leaves.
The larvae feed voraciously before pupating into adult bugs that overwinter in soil or plant debris, to emerge again in spring and start the cycle again.
Lily beetles are good at camouflage and protection. When disturbed, they drop from plants and lie upside down, where their dark undersides are hard to spot against the ground.
The larvae have an unappealing habit of covering themselves in their own excrement, both for camouflage and to deter predators – plus it puts gardeners off picking them from the plant.
The Signs of Lily Beetles to Look For
Lily beetles feed predominantly on lilies and fritillaries, and these are the only plants on which they lay eggs and complete their life cycle. The pests are known to feed on lily of the valley, Solomon’s seal, nicotiana, hollyhock, and potatoes, but not daylilies, canna lilies, or calla lilies.
Adults and larvae mostly eat the foliage, but will also target stems and developing buds at times.
Lotte Berendsen, an expert from the PlantIn app, explains what to look out for during the season. She says: ‘The adults leave small, circular holes in your lilies’ leaves, while the larvae feed away at the bottom, leaving dry and brown patches.’
‘You may find tiny orange-colored eggs on the bottom of the leaves; they are usually laid in clusters,’ adds Lotte.
In most cases, lilies can cope with the damage, provided action is taken. However, large infestations can defoliate plants, destroy flowers, and ultimately cause the lily to not bloom the following year.
It is advisable to monitor plants in the spring for signs of early damage and the presence of eggs. The key times to be vigilant are in April and May when the beetles emerge, and from May to midsummer, when the adults start laying their eggs on the underside of leaves.
Lotte is a gardening enthusiast, writer, and plant expert at PlantIn, where she provides customers with detailed care and treatment plans.
How to Control the Lily Beetle
The best way to control lily beetles is to handpick them from the plants. Scour the leaves (including the underside) and pick them off, dropping them into a container filled with soapy water.
If you place a light cloth or piece of paper under the plant, you’ll be able to spot any adults that drop off and roll over to reveal their darker undersides. Remember, gloves are definitely recommended for handpicking larvae and their unsanitary habits.
An organic, unconventional way to control lily beetles is to spray the plants with sunflower oil. Brandon Runyon, an entomologist with Swat Pest Management, explains how sunflower oil works through suffocation. He says: ‘The oil blocks the spiracles, so the beetle cannot breathe.’
Lotte Berendsen adds that while 100% sunflower oil works best on larvae, it will impact adults, too, just not in the same way.
‘Sunflower oil works best on larvae, as these are soft-bodied and vulnerable,’ she says. ‘It also creates a barrier on the leaves, making it harder for both the larvae and the adult beetles to feed. But adult Lily Beetles have a shell that can protect them.’
Spraying sunflower oil only treats active infestations, rather than being preventative, and only has a temporary effect, so it would need multiple applications. You can get bottles of organic 100% sunflower oil at Walmart.
There are cautions to using sunflower oil to control lily beetles. Primarily, be careful what you spray, as it could also harm beneficial insects if they are caught in the crossfire. But, overall, the oil won’t have long-term impacts on insects in the garden.
Both insecticidal soap (get ready-to-use insecticidal soap at Walmart) and neem oil (get ready-to-use neem oil at Amazon) have been shown to kill larvae. However, these also pose risks to other soft-bodied insects and will need to be reapplied at least once a week.
There are other recommended natural pest control methods. If you grow lilies as part of a wildlife garden and use companion planting to attract birds, beetles, and frogs to your yard, these are all natural predators of the lily beetle larvae and will help to control populations.
Brandon Runyon has 20 years of experience in Pest Control and is a Board Certified Entomologist.
This mix of lily bulbs features Oriental, Tiger, Asiatic, Trumpet, and species type lilies in a range of colors and sizes.
This product is approved for organic gardening to combat a wide range of pests, including lily beetles. It claims not to significantly impact beneficial insects.
Whether handpicking lily beetles or spraying for pests, always protect your hands with gloves. These gardening gloves are soft, comfortable, and durable.
For showstopping displays from your lilies year after year, it is advisable to feed them. You should fertilize lilies in spring to give them all the nutrients they need for the summer blooming. The best type of feed to use at this time of year is a balanced fertilizer, such as this 10-10-10 plant food at Walmart.
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