Lily Pests and Diseases
What a beautiful day. As we are enjoying this unseasonably warm weather I thought now would be a good time to revisit the problem of the lily beetle. Not only do they affect lilies, but your fritillaries can also be at risk. The general consensus following last year’s email is that with some precautions they can be controlled in the garden. The earlier action is taken the better.
Before moving on to the lily beetle a quick mention of other, if rare, threats to lilies is worthwhile.
This can occasionally affect lilies most notably when growing in cool shady positions. It is first observed as brown spots developing on the leaves which turn grey and spread out to affect the whole of the leaves and the stem. The bulbs will not be affected and should be replanted in a sunny position for the following year. A dusting of sulphur on the bulbs before replanting will help prevent future problems.
Although this problem rarely occurs the have been known to attack the roots causing the pant to yellow and become stunted. A heavy watering around the bulb with a solution of common salt should help.
Occasionally troublesome especially if the weather has been particularly wet where they will attack the young green shoots.
And now the Lily Beetle.
The red beetle overwinters in the ground and emerges from late March as the ground starts to warm. Their eggs are laid on the underside of the plants leaf from late April until mid-summer. This is when the damage starts as the larvae feed on the foliage. When done they return to the ground to pupate, leaving a covering of what looks like bird droppings on top of the soil and emerge as adults in mid-summer when they carry on the feeding damage.
The aim is to initially try and stop pupation and then to kill any surviving adults in mid-summer. Year on year this will substantially reduce the problem. This should be a local project as the ground they choose for the winter is not restricted to the immediate vicinity of the plants. There is some evidence that they are attracted to the plants by scent, hence their spread.
Despite RHS sponsored research in 2004, there was very little practical advice for the eradication of this pest. Science is not always helpful in our gardening practices, horticulture is generally too far down the food chain to claim the required resources. Much of what we do has to be based on experience, passed along tips and trial and error.