Saturday, March 5, 2011

Slither, Slither....

Whenever gardeners gather together in spring, sooner or later the conversation comes around to slugs, those destroyers of horticultural dreams. So, bearing in mind the words of the 6th. century BC Chinese military strategist Sun Tzu - "If you know both yourself and your enemy, you can win a hundred battles without a single loss" - here are pictures of two of the worst offenders. Double-click for larger images. First up, the netted slug Deroceros reticulatum, which so often crawls into lettuces. The colour can be quite variable but this pale grey and buff form is common in my garden, but...


... the ID character that gives this slug its common name is the dark network pattern on the tail end of its body, which you can just see in this view, at the back of the animal.

And here's another slug that will be slithering out in search of tender young seedlings as soon as mild, moist spring days arrive. This is the Budapest slug Milax budapestensis. In this view you can see the open breathing pore (the pneumostome) that leads to the slug's lung. Those little parasitic nematodes that you can buy to kill slugs, as an environmentally-friendly alternative to slug pellets, crawl in through there, breed and kill their host.

The Budapest slug has a distinctive yellow keel that runs along the top of the rear half of its body.....

... and the pneumostome is located towards the back of that 'saddle' at the front of the body, while.....


... the dark stripe that runs along the underside of the foot is also a distinctive feature.

One of my project students, Jack Brooks, is currently investigating whether there are any natural extracts from plants that might be used to deter slugs (they are supposed not to like garlic, coffee and extracts of ivy leaves) that could be used to protect vulnerable seedlings in spring. He's also looking at which garden slugs are damaging and which are harmless to plants - the leopard slug (sometimes called the great grey slug) is supposed to be blameless as far as damage to garden plants is concerned. We'll report back on how the research goes....

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