VAL BOURNE says there can only be one way to deal with the menace of the lily beetle

Gardeners hate bright-red lily beetles and I am constantly being asked how to deal with them in a green way. There's only one method and it's brutal - pick the conspicuous creatures off and kill them. But there's a problem.

Once you touch the bright-red beetles they fall and land on their backs and then many gardeners find their dark undersides difficult to spot against the ground. If you do have them, track down the clusters of red eggs now and destroy them. They are found only on the leaves of lilies and fritillaries.

Once the larvae hatch in late spring they cover themselves with their own black excrement. This makes them look just like bird droppings and they are slimy to touch, to put it politely.

Once you have one or two lily beetles it's hard to prevent a real outbreak because affected plants exude a characteristic smell which attracts other passing lily beetles. It's an open invitation to join the feast.

Despite growing lilies in pots I have never suffered from these pests probably because my garden is high and exposed. Lily beetles seem to prefer built-up areas, or areas which have a clement climate. They are much more prevalent below the Pennines, for instance. The Royal Horticultural Society website (www.rhs.org.uk) has an up-to-date distribution map.

The scarlet lily beetle, Lilioceris lilii, isn't new. It's been around for nearly 70 years and was first noticed in 1939 when a colony was recorded in a private garden at Chobham in Surrey.

By the late 1950s the beetle, which came from Asia probably on imported lily bulbs, had become widespread in Surrey and was also found in Berkshire. By 1990 the beetle's range had extended into Oxfordshire, Hampshire, Middlesex, Wiltshire, Dorset and Hertfordshire. By the end of 2006 this pest had been found in almost every English county.

Recent reports sent to the RHS indicate that the beetle is established and spreading in Scotland and Northern Ireland.

The RHS say that "up to quarter of amateur gardeners have experienced the problem" so it's probably safe to say that its range will extend and affect even more of us.

However, in parts of mainland Europe the lily beetle is kept in check by four species of parasitic wasp that attack the larval stage. But only two of these are known to occur in the UK, Tetrastichus setifer has been present for centuries. But Lemophagus errabundus was only found in Britain in 1999. There obviously aren't enough predators at present to control the problem.

April is a key month to find and destroy the eggs and at this time of year it's vital to check any fritillarias suffering chomped foliage, flowers or stem. April's Gardening Which suggests treating lilies as annuals and buying cold-stored bulbs in late May. By the time they get into leaf the beetles are less prevalent.

There is a guided walk and high tea at Waterperry Gardens, near Wheatley, on Thursday at 2pm. Tickets must be booked in advance and cost £15. Visit www.waterperrygardens.co.uk or call Jenny Braithwaite on 01844 208073.