Avoid Disaster! Check your plants for Solomon’s Seal Sawfly today

Solomon's_Seal Sawfly larva

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.

Polygonatum

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.

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11 Replies to “Avoid Disaster! Check your plants for Solomon’s Seal Sawfly today”

  1. Yuk! It’s pest time!

    1. Sadly, yes it is pest time BUT they are interesting things and , in a perverse sort of way I love ’em!

  2. Can’t say I had heard of this one. I’ll keep any eye out!

    1. Definitely worth looking out for it, and regularly too, it can devastate very, very quickly!

  3. Can I treat the soil ? hoping to prevent the larvae starting the cycle again?

  4. Yes – treat the soil with nematodes as directed on the packet – they use the larvae as a host and eventually kill them.

  5. I am rather fond of the sawfly as it is actually a beautiful little insect and part of our country’s biodiversity. There will no need to pick the caterpillars off if you do this one simple thing: The female sawfly deposits her eggs under the skin of the stem, usually in a fleshy lower part. You can see where this is done because a discolouration develops. If you simply rub your finger over this, you can feel the eggs popping. This is every bit as satisfying as popping bubble wrap and a lot easier than caterpillar hunting. So, regularly just run your thumb and forefinger up the stems and you’ll kill the bugs before they get started and will even be left with clean hands!

  6. What eats the sawfly caterpillars? If I pick them off and put them on the bird table will my bird visitors deal with them for me?

  7. Why not leave them be. The bird and insect populations in the UK have plummeted over the last 30 years and we are heading for a silent spring!
    The birds need insects to feed on and the insects pollinate plants, all important for our own well being.

  8. is there a best time of year to apply nematodes

    1. you can apply nematodes any time really as long as there is no frost about and the ground isn’t frozen (not much chance of that in this heatwave 🙂 ). Best to apply them when the grubs are about so the nematodes can get to work immediately also best to apply them at night on moist soil

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