The Infestation

Dear Readers, I am off to Austria at what is officially known as ‘stupid o’clock’ tomorrow, so here is my Saturday blog on Friday night. Wednesday Weeds will continue as normal for the next few weeks, but my Saturday blogs may have a Tyrolean feeling…..

Dear Readers, going to  Canada for two and a half weeks in April is not ideal from a gardener’s point of view. When I came back, the garden had turned into a jungle, the pond had become a bog, and I have been fighting to get things roughly back under control every since. And now we’re off to Austria for another two weeks, and there’s some rainy weather forecast. I shall have to hone the machete for our return.

It’s not just that everything has grown, either. Growing is fine. What if the bramble at the back of the garden is now dangling over, heavy with blackberries? What if the hedge, trimmed only last year, is now too high for me to reach and I have to send my husband out with a step-ladder? What if, in spite of the sterling work of the man who comes to look after the cat, the pond is a more-or-less complete carpet of duckweed? These are all things that can be remedied with a bit of sweat and a pair of secateurs or a net.

No, what worries me are the uninvited guests.

Take a look at my great willowherb. I have allowed a fine stand of it to grow next to the pond, because the bees love it, and its bright pink flowers are cheerful. However, I doubt that we will get many flowers at all this year, because a tiny seamstress has been at work. The leaves of almost every shoot have been stitched lovingly together, turning each bud into a fat purse.

My great willowherb in happier days….

The ‘purses’ are so well sewn up that it’s actually quite difficult to open them, and when I do, it’s clear that there’s somebody at home.

Mompha epibiella caterpillar, snug as a bug

So, this little chap is a caterpillar. There is a vast group of tiny moths ( called micro-moths) who go about their business largely unnoticed. Some of them are so small that they can make their homes between the layers of a single leaf – you can often see their trails wandering about in plants like sow-thistle. Horse chestnuts in the UK have their own delightful leaf miners, which are turning the leaves brown even as I speak.

Slightly larger micromoth caterpillars make their homes by stitching leaves together, burrowing into stems and buds or eating their way into roots. They can be polyphagous (which means they eat lots of plants) or much more picky. Some live only on birches, some on roses, and some only on willowherbs. My gut feeling is that the culprit in my garden is Mompha epilobiella, a rather drab moth which specialises in  the Epilobium (willowherb) family.

By Donald Hobern (Flickr: Mompha epilobiella) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Mompha epilobiella (Photo One – see credit below)

When I say ‘drab’, however, it’s more a reflection on me than the moth. Here is the same species, spread-eagled as a specimen (poor thing). The wings are edged with long ‘hairs’ called cilia – these interlink in flight to give a bigger surface area for lift, and make the moth appear to be trailing clouds of glory. How intricate these tiny creatures are. I think that calling any living thing ‘drab’ indicates a failure of attention on my part.

By Michael Kurz (Own work) [CC BY-SA 3.0 at (http://creativecommons.org/licenses/by-sa/3.0/at/deed.en)], via Wikimedia Commons

Specimen Mompha epilobiella (Photo Two – credit below)

The caterpillars are protected while they are at their smallest and juiciest in their bivouac of leaves. Other members of the Mompha family also like willowherbs, but will mine the leaves rather than stitching them together, or live in the stem, so there is no direct competition. I do wonder why the blue tits haven’t worked out what’s going on, as they are highly intelligent little birds, but maybe it’s too much effort when there are other exposed caterpillars about. The caterpillars are also protected from the various wasps who would love to feed them to their offspring. What a successful strategy for such a small, otherwise defenceless creature.

Av Stainton - http://www.biodiversitylibrary.org/bibliography/25081, Public Domain, https://commons.wikimedia.org/w/index.php?curid=16901734

An 1873 drawing of a Mompha epilobiella caterpillar (Photo Three – credit below)

However, when the caterpillars pupate and drop to the soil, they are at their most vulnerable to attack from the wasps who couldn’t penetrate their leafy sanctuary. Those that survive will overwinter as adult moths, ready to launch into another campaign as soon as the weather warms up. However I fear that they will have to search elsewhere: I was planning to pull up the willowherb this year because I can no longer see the pond from the house, and plant something a bit more low-growing. There is no shortage of willowherb around here, so I feel only slightly guilty. I had hoped for elephant hawk moths, but when you plant a wildlife garden you really do have to be ready for whatever turns up.

In North America, great willowherb is a noxious weed, and there has been some excitement at the arrival of Mompha epilobiella. It’s hoped that the moth will keep the willowherb under control (and I suppose that the arrival of a natural predator, even an alien one, might be a cause for rejoicing). However, the local parasitic wasps have already discovered that the pupae make a delightful home for their larvae, illustrating how the arrival of non-native species can cause a whole series of unexpected effects.

When we tend a garden, what we are really doing is facilitating a whole host of living things, providing opportunities for them to thrive. And boy, do they take advantage of what we do. We slightly disrupt or add to one part of the complex web of relationships, and the next thing we know we’re inundated. It will be interesting to see what happens as the summer moves on – will the willowherb bounce back, or will it languish? Will I see lots of new tiny parasitic wasps? And when I clear the willowherb area, what will come into the garden to feast on whatever I plant next? Life is certainly full of surprises.

Photo Credits

Photo One (Live moth) – By Donald Hobern (Flickr: Mompha epilobiella) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons

Photo Two (Specimen) – By Michael Kurz (Own work) [CC BY-SA 3.0 at (http://creativecommons.org/licenses/by-sa/3.0/at/deed.en)%5D, via Wikimedia Commons

Photo Three (drawing of caterpillar) – Av Stainton – http://www.biodiversitylibrary.org/bibliography/25081, Public Domain, https://commons.wikimedia.org/w/index.php?curid=16901734

 

3 thoughts on “The Infestation

  1. Toffeeapple

    It really is amazing what turns up, isn’t it? I have managed to get rid of Lily Beetle by no longer having Lilies but nature has given me, instead, smartly dressed Rosemary Beetles!

    Reply
    1. Bug Woman Post author

      🙂 there’s always something, eh. I rather like Rosemary Beetles with their green and purple stripes, there are always a few on my lavender plants, looking like little drops of molten metal…

      Reply

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