Lily Beetle - plant pest
also known as red lily beetle or scarlet lily beetle

If you grow lilies - you MUST be aware of this pest and look out for it - wherever you live

Signs - Like the name suggests lilies (from bulbs) are the main plant that are attacked, though fritillaries, soloman's seal, day lilies and lily of the valley may also be eaten. The adults and larvae eat the leaves and unopened flower buds, despite the fact that the adults are bright scarlet they are not easy to spot on the plants. They are black underneath and spend most of their time under leaves so are surprisingly inconspicuous.

If you are growing lilies, you need to look out for them from the point that the shoots appear in the spring. Look at the leaves for cleanly cut scoops in the side or holes. The easiest way to see the adults I find is to bend at the waist and turn your head upside down so you are looking up the stems and at the bottom of the leaves rather than down on the stems, alternatively lay down on the ground next to your lilies and look upwards. If you find one lily beetle, you can bet you'll get lots more. The overwintering adults arrive first emerging from the soil to lay their eggs in early to mid spring once there are lilies to feed on. The larvae then appear and cause the real damage.

The larvae are very inconspicuous as they cover themselves with sticky black excreta which if you've never seen them before doesn't look anything like an insect that can devour your lovingly cared for lilies in next to no time.

The eggs are tiny, but are bright orange/red and laid in groups of up to 15, so they are surprisingly easy to see for their size - they are only laid on the underside of leaves.

These pests can destroy your prize lilies in a very short time - if you grow lilies, you have to be vigilant.

Damage - The beetles, both adult and larvae have a particular liking for the emerging flower buds, so the years flowers can rapidly be completely destroyed before you have even seen them unfurl as small buds. They will also start on the leaves and strip them. The bulb may be able to lay down reserves for next years flowers if it has leaves (but how disappointing to find out the buds have been pinched out just as they were about to do their thing), though not if the leaves are also removed.

Treatment - A two pronged attack, pick off and crush the adults underfoot and use a systemic insecticide on the plant which is most effective against the larvae.

As mentioned, the adults are surprisingly good at hiding for a bright red 6-8mm long beetle. Look under the leaves, pick them off and tread on them, this may affect your sensibilities, but it is organic! Once you've had a favourite lily attacked by lily beetle, you will find it easier to pick them off and tread on them.

A systemic insecticide applied every 4-6 weeks according to instructions is the most effective means of combating lily beetle. This kind of insecticide is taken in by the leaves and distributed around the plant, when the adults or larvae eat the plant, they eat the insecticide and are killed, it is also residual within the plant for this time.

The lily beetle was a relatively localized pest in south east England, especially in and around London until about 2000. In the last two decades it has spread throughout Britain and is now established as far north as Scotland and Northern Ireland.

While they can be a particularly devastating pest, they are readily dealt with as long as you are aware of them and are looking out.