Solomon’s Seal Sawfly
Keep a close watch on your plants for sawfly damage at this time of year. Solomon’s seal is unlucky enough to have a particularly serious sawfly pest whose larvae can strip it or the related Polygonatum plants bare. The larvae feed in groups so severe damage happens very quickly as the greyish white caterpillar-like larvae munch their way through the leaves. Most of the damage happens from May through until early August, but this feeding period may differ slightly from area to area and from one season to the next.
The adult sawfly has a special organ called an ovipositor which is able to cut into the plant so that she can lay her eggs into the leaf stalks; you may see purple-brown ‘scars’ indicating where this happened – a useful warning sign that you’re likely to see an outbreak of the larvae.
Towards the end of the season these (now well fed) larvae will move down the stripped-bare plant and in to the soil where they pupate and so successfully overwinter, ready to emerge as adults next year. A devastating cycle!
Regular checks on Solomon’s seal and Polygonatum plants should mean that you can remove the larvae as they appear and before they do too much damage. Alternatively you could treat with a proprietary caterpillar spray or, better still use ‘Nemasys Fruit and Vegetable Protection’, a wonderful mixture of nematodes which controls a range of common pests, including sawfly (you can find out more at www.pippagreenwood.com/products/protect-your-crops. This can be used not only on ornamental plants like Solomon’s seal and other flowers suffering sawfly attack, but also on gooseberries, should yours succumb to one of the gooseberry sawflies. These are a very common and widespread pest and will also strip a plant bare within hours, usually just leaving the tougher mid-veins of the leaves in place!
Whether it is ornamental plants or edibles that are under attack from sawflies, they are unlikely to be killed but the loss of so many leaves will mean they are put under a lot of stress so once the pests are sorted, do all you can to give the plants a bit of extra TLC by providing plenty to drink, a bit of general fertiliser and maybe even a mulch of well-rotted manure or garden compost.