I have a viburnum bush. This year, for the first time, most of its leaves have been badly chewed. I cannot see any bugs. Can you tell me what is causing this and what I can do about it?

Your viburnum has been attacked by the viburnum leaf beetle, a fairly recent arrival to this part of the world which accordingly has no natural predator. The beetle does a dramatic job of skeletonising the leaves of certain viburnums (see the picture at the left) while ignoring others. The damage can be so extensive that, if not controlled, it will eventually kill the shrub.

There is a very good site discussing the management of this pest at the Cornell University site. An important part of their advice is to refrain from using strong general-purpose insecticides, as they are not effective and they destroy beneficial insects. There is also information on the BC Ministry of Agriculture and Lands website. This is not an easy-to-kill pest, it is a question of minimising the damage.

When buying a viburnum, select one that is less susceptible to attack, such as Viburnum carlesii, the Koreanspice viburnum or Viburnum x bodnantense.

I'm having a problem with my day lilies. Some of the buds are turning to mush and not opening. What is causing this problem and how can I avoid it in the future?

The day lily flowers are being chewed up by the larvae of the day lily gall midge. The picture to the left shows one normal bud, above, and two infected buds, below. There is information on the BC Ministry of Agriculture and Lands website. The most effective method of control without resorting to systemic pesticides is to remove any misshapen buds and dispose of them in the garbage. If you slice through them you will see little white maggots. It is important not put infected buds in the compost or elsewhere in the garden.

Fortunately the midge's life cycle means that the maggots will not be present in buds after July and late buds will not be affected. But it is important to to get rid of all the larvae. Any remaining ones will fall to the ground and pupate, hatching next year to grow in next year's flowers.

Next year check the flower buds every few days for signs of infestation, such as swollen bases on the flower buds. Persistent removal will at least keep down the numbers of this pest, and it is hard to get at it with insecticides, even the toxic ones.