Page 16 - Simply Vegetables Autumn 2024

Slugs
KELVIN MASON
Slugs have been a bad problem this year owing to last winter’s wet weather and this year’s wet spring and in parts of the country a wettish summer; these damp conditions are ideal for the pest.
I recently read an article in Farming Weekly magazine (no I am not moving into farming!) in which they were saying that a changing climate and farming systems could lead to more frequent slug population explosions and that growers need to be aware and ready to take action as its required.
The article states that U.K winters
are getting milder and wetter as was shown last winter which creates the
ideal conditions for both feeding and overwintering and can lead to crop failure (I speak from experience having lost three rows of carrot this spring and having to resow them.).
It is predicted that slugs could be a problem again this autumn and winter especially if mild. The main slug species that cause growers problems are the common keeled slug, garden slug and grey field slug.
There are many other species but as Roger Clement comments in his letter in this issue they are not all considered bad, some feed on organic matter and others appeartofeedonotherinvertebrates including being cannibalistic on other slugs! We need to learn more about this so wecantrytoretainthegoodiesandjust get rid of the plant eating pests.
Slugs are hermaphrodites (meaning they have both male and female reproductive parts) and can produce asexually as well if no mate is present. They lay 10 to 50 eggs at a time and over a season and over its lifetime one slug can lay 100 to 500 eggs, its life time is approx.. 6 to 18 months. It is this fast and high breeding that leads to them being such a problem in the garden.
Slug damage
The eggs are laid close to the soil surface in dark damp places like holes or crevices in the soil or under wood or hardcore on the soil surface. In the right conditions when the slugs hatch and start to feed they cause significant damage and can kill up to 50 seedlings within a week of sowing.
Minimum cultivations or no-dig can increase slug populations as the soil surface is not disturbed by digging so none are killed or made available to predators. This is particularly the case if crop remains are left on the soil surface or green manure is cut and dropped on the bed as this provides both a shelter and food source for the pests.
The trend in pest and disease controls these days is IPM (Integrated Pest Management) which is basically using a numberofmethodstocontrolthepests before using chemicals; so what is the IPM approach to slug control?
or slime trails or actual slugs.
• Trapping, there are various baits that
can be used to trap slugs including beer, lager, and orange halves, melon skins, chicken layers mash, cardboard laid on the soil, etc. the traps need checking every day preferably in the morning and any slugs killed. Trapping is a useful method of monitoring for slugs as if you are catching more than four in a trap you have a slug problem and need to take further action. If a polythene sheet is laid over the soil surface prior to sowing many slugs will congregate there and when the sheet is removed the slugs can be collected up and disposed of.
The following risk factors can influence slug populations:
• Moistureandtemperatures–outdoors there is not a lot we can do about these but noting them can give
• Notethepotentialrisk factors associated with slug damage
– this can include weather conditions as mentioned above, previous crops, previous damage in the area and the next crop.
If you are catching more than four in a trap you have a slug problem and need to take further action
awarningofpossible problems ahead. Slug activity, survival and reproduction all depend
on moisture so if areas
are kept dry using cloches or other means this can help. In greenhouses and polytunnels water around the plants but try to keep as much of the soil surface dry as possible. The optimum temperature for slugs is 17̊ C but the grey field slug active at near to freezing,
• Consider the most
suitable cultural
control techniques
this includes clearing
any debris / crop remains, remove any potential habitats like piles of sticks, hardcore, long vegetation where slugscanlive.Thetrendtorewilding, no-mow May and other techniques to encourage wildlife into the garden can also encourage slugs and other pests!
can still be
while other species are only active above 5 ̊C.
Slugs
• Monitoring crops, check your crops dailyifpossible(notalwaysiftheyare at the allotment!) or as often as you can and take action as soon as signs of a problem shows like plant damage
• Soiltypes–heavyclaysoilsholdmore moisture and tend to be cloddy which provides ideal conditions for slugs and egg laying sites therefore slugs tend to be more of a problem on clay soils.
• Previouscropping–iftheprevious crop has been dense and leafy this can encourage slugs as it can provide a moist, shady site with a good food
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