Slugmageddon, not to mention snail hell

The 2016 growing season has been particularly difficult for anyone trying to grow organicallyand at BOG we have been hard hit – so much so that the harvest of dwarf  and runners will be considerably less than a hill of beans. Despite three sowings, each of them were reduced to skeletons.

The culprits are all molluscs but it is difficult to know whether the slugs or the snails have done more damage. Obesity certainly seems the fashionable look  for all of them this year.


Eat any more and you’ll never get back in your house

It’s probably a combination of a mild winter, and subsequent weather conditions which have generally favoured their population explosion throughout the growing season.

In addition our own actions have created an eat-your-fill feast for them: soil full of organic stuff to eat when they hatch underground, and hundreds of succulent plants waiting to be nibbled to death. And molluscs tend to be pretty parochial. If there is food on the doorstep why wander?

[This may also explain that infuriating thing where someone starts a veg garden and has stupendous success where his neighbour, having cultivated and fed his plot for years finds his crops in tatters. I like to think this is because the slugs and snails haven’t built up a population on the new plot. The following year it might be a bit more difficult, especially if the new plot is fed with farmyard manure, which may well contain slug and snail eggs.]

But the fightback is at hand. Len Fawcett has been visiting the garden at dusk and in one visit collected more than 200 of the offenders, which he then sentenced to some salty water.

That is one recommended organic way to conquer such an invasion. But it takes time and many repeated visits, especially on warm wet evenings. And it is doubly unpleasant to have to pick the slimy things and then to kill them. And to be effective you have to do it for at least six weeks, to catch new slugs as they hatch. Some commitment, even if you live close to the garden.

Another solution is to introduce the slugs to a few million parasites that get them before they get our veg, and that is now our plan. We are buying a double treatment of Nemasys, about 25 million nematodes that will be watered on the parts of the garden worst affected by the invasion.

The mixture delivers about 300,000 nematodes per square metre and they attack the slugs immediately, so that they lose their appetite and die underground within a week. A second application six weeks later catches the slugs that are emerging from eggs laid by the earlier generation.

Slugs are generally active when plants start growing and soil temperature is over 5ºC. Young slugs tend to stay underground, feeding on decaying organic matter, (like the manure we liberally use) developing unseen and waiting for young seedlings to be planted. They breed all year with two overlapping generations and peak egg laying is Mar-Apr and Sept-Oct.

Although we missed the first egg- laying we will be in time for the second peak and this should decimate the population that survives the winter. We plan to treat the plots with another dose of Nemasys next spring, just to be sure. It’s not a particularly cheap solution but it will be worth it to see our crops thriving next year.

That’s all very well for the slugs but the snails are a different matter. Because nematodes only work underground the snails tend not to get infected. In a perfect world we could rely on a couple of dozen thrushes to clear the ground but without them it looks like hand-picking is the only alternative for them.

That can be done in the winter when there is not a lot going on. Just identify the places where the snails congregate to hibernate – under containers or stones, and in dark places throughout the garden – and you can pick dozens in one go.



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