Wednesday, June 28, 2017

Scarlet lily beetle

This year, for the first time, scarlet lily beetles Lilioceris lilii appeared in my garden. There were only two, which turned out to be a male and a female, and they came with some lily bulbs imported from Holland that I bought in a supermarket.

Being curious, I kept them under observation in a jam jar and soon discovered why these lovely insects are considered to be such notorious pests.

They mated overnight and by the next day had begum to lay rows of their round-ended, cylindrical eggs on the lily leaves that I supplied to them.

The adult beetles are formidable eaters, quickly nibbling holes in the edges of leaves that I gave them to feed on, but the grubs, when they hatched a few days later, were in a different league altogether.

They quickly began chewing holes in leaves and half a dozen of them could demolish a lily leaf in less than a couple of hours.

But, most remarkably, they did this while covering themselves in their own frass, which camouflaged them as bird droppings. This one has only just begun to anoint itself but they quickly became completely hidden in a mound of their own droppings.

From a gardener's perspective, these are extremely destructive insects and I can quite see why, in the worst affected parts of the country, gardeners have had to give up growing lilies. 

These gaudy insects have spread from their native Eurasia throughout most of the temperate northern hemisphere.  They first appeared in England in a Surrey garden in 1939 and by 1943 had reached the United States. Their spread northwards in England, and now into Scotland, has been rapid in the last decade, no doubt helped by a wholesale and retail distribution system for lily bulb sales that has ensured that they can reach every part of the United Kingdom.

I never once saw them attempt to fly. If you disturb the adults they just fall off the plant and pretend to be dead until the danger has passed.

The Royal Horticultural Society has a very good web page devoted to these insects and is also conductiing a survey of their spread, although I have to say the words 'horse', 'bolted' and 'stable door' come to mind!

These two individuals were the only ones that appeared in the garden and my lilies are doing fine, almost flowering in fact, but I wonder whether I'll be so lucky in future years


  1. I'll keep an eye out. Impressive beetles and hard to miss.

    1. They really are, Adrian. When they are fully fed the grubs crawl down into the soil and pupate. There's only one generation a year but they are easy to spot - just look for lilies that have been shredded and seem to be covered in little piles of poo!

  2. I had to stop growing Lilies because of them, they are so destructive.

    This year I have seen, for the first time ever, Rosemary Beetles! They look very smart but I don't know how much damage they will do to my Rosemary plants.

    1. I haven't seen a rosemary beetle yet but they do look very colourful. I grow quite a lot of rosemary, for cooking, so I'm keeping a lookout for it.


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