Scarlet Lily Beetle (Lilioceris lilii)

What are Lily Beetles?

These beetles are easily recognised as although they are small as they have as the name suggests are brilliant red coloured.  They are between 6 and 8mm in length and have black head, legs and antennae.  The adults spend the winter beneath ground after which they appear and are active from the end of March to the autumn and mate from then till the autumn.  The adults lay their orange/brown eggs in small groups and after emerging into grubs, smoother themselves in excrement in order to deter predators.  They tend to feed in groups on the leaves and stems of the host plant starting at the tip and working back to the stem, stripping the plant bare.

Although the Scarlet lily beetle is not a native to Britain, it is a native to parts of Eurasia.  It is thought to have been imported into Britain in the 1940s on imported lily bulbs.  It is an established pest in the south of England but it is only in recent years that it has spread to the northwest of England.

Do they harm plants?

Yes

What damage do they cause?

Check for holes appearing in plant foliage in spring and early summer.  If left untreated, damage will increase throughout the year and severe loss of leaves will mean that the bulbs beneath the ground may not increase in size therefore preventing  flowering of the plant the following year.

Do they affect certain plants?

Yes; Lilies (Lilium) and their hybrids along with species of fritillaries (Fritillaria).

Is there any time of year particularly at risk from them?

The end of March/Early April then through to autumn.

How do I get rid of them?
 
Non-chemical control

Keep your eyes out for the beetles on your plants.  The scarlet adult beetles are pretty easy to see due to their colour but also keep your eyes open for their eggs and grubs.  They have a habit of just dropping off the plant when threatened so pick them off carefully!  The adults emit a high pitch squeak, when disturbed.  It is thought that this is done to warn other beetles of danger in much the same way birds do.


Chemical control

Plants which have become infected can be sprayed with imidacloprid mixed with sunflower oil.  Products containing any of the other following will be effective also: Bifenthrin, Pyrethrum, Natural fatty acids, Surfactant-based products.  The adults are less likely to be succumb than the grubs.

Always use chemicals as instructed on the label and wear any gloves etc. when necessary.