Bug Control (Slugs)
Slugs along with Aphids are probably the most common and hated garden pest of all. To my mind there are few redeeming features to slugs in any sense. I know they are responsible for breaking down organic material but so too do many other creatures, who do it without the collateral damage that slugs deliver. The claims that they do have some 'attractive' markings is, I'm afraid, completely lost on me.
Historically, the first thing that usually comes to mind when trying to deal with them is by using slug pellets. Slug pellets are a bit like ‘Napalm’ for gardens. They are notorious for not just dealing with slugs but also harming pets and slug predators in the form of birds and Hedgehogs.
As I've mentioned in a previous blog, in my Essex garden, I’ve banned all forms of chemical weapons, so at all cost I avoid reaching for a chemical solution and look for alternatives and there are quite a few ways you can deal with Slugs
But before I launch into some organic methods, I would like to give my view on products that use pellets of some kind.
Of the more recent chemical deterrents one that comes to mind is the comically named “Sluggo”.
This slug and snail killer is one form of this deterrent that is promoted as being safe for the environment, which as anyone who reads information provided by the commercial world knows, can be a bit of a ‘grey’ statement. Its application is simple, just scatter 5g/m², preferably in dry conditions, with no waiting time for harvesting of plants [BOP information].
The main chemical ingredient of “Sluggo” is Iron-III-phosphate, which the manufacturers claim will breakdown in the soil naturally, however following some research I did on the web the product manufacture may involve the use of the chelating agent EDTA (Ethylenediaminetetraacetic acid). Now there is no statement relating to this agent on the “Sluggo” website, but a paper produced by FiBL (Research Institute of Organic Farming) states that Iron salts have virtually no effect on slugs unless combined with EDTA. Therefore 'if' it does indeed contain this chelating agent, I've read that this will leech heavy metals from the soil into ground water. How this happens and to what degree I can't say, but it's something to think on. [Tamm, L. Speiser, B. (2006)].
The manufacturers of “Sluggo” claim it is ‘safe’ but information on the internet regarding Iron Phosphates is conflicting. There appears to be a great deal of ambiguity as to whether this chemical is ‘totally’ safe. Sluggo now has the “Organic material research association” logo on the pack so it can be used by Organic farmers, but gardeners may not be so assured by this ruling. “Sluggo” also contains Spinosad, which although is a natural bacterium, kills all kinds of insects including Rove Beetles, which are natural predators of slugs. So, whilst it may be a very effective solution it may eliminate additional natural defences against slugs, which could mean its usage may need to increase as more and more of the slugs natural predators are eradicated.
So, the benefits of this type of control is that they can convenient to use and be very ‘effective’ on Slug numbers, but the disadvantages are that there is evidence that they can be dangerous to slug predators and earth worms too. [Edwards, C. Arancon, N. Vasko-Bennett, M. Little, B. Askar, A. (2009)]. For me, personally if there are reasonable alternatives I'll stick with my 'no chemical weapons' policy
Organic control of Slugs
If you have decided to deal with slugs organically, the good news is that there are multiple ways of doing this. The most obvious being to make your garden the friendliest place possible for all slug predators such as hedgehogs, birds, frogs and predatory insects. This would include providing plants that give birds a good supply of berries, installing bird baths and bird feeding tables and creating a wildlife pond to encourage frogs or toads. This would also be useful for hedgehogs to drink from, as long as there is safe access to and from the water. Another idea is to set up ‘Hedgehog houses’ or undisturbed log piles to give hedgehogs a safe haven and insect “hotels” to support all the predatory insects through winter.
Back in the 'old days', gardeners always had pots of salt to sprinkle on slugs, killing them pretty instantly but this also damages the soil, so not recommended.
Coffee grounds deter slugs when sprinkled around your plants. This may also bring other benefits in regard to composting. Fresh coffee grounds will add nitrogen to your compost, although it doesn’t immediately add nitrogen to your soil. They also lower the soils ph level (making it more acidic), however ‘rinsed’ coffee grounds are near neutral. Coffee grounds will also attract microorganisms beneficial to plant growth as well as attracting earth worms.
I can’t find any evidence that the worms become hyperactive after contact with coffee grounds either!
Another well documented slug trap is to cut off the bottoms of plastic bottles or a similar form of tray, which is then filled with beer and sunk halfway into the soil.
The slugs are attracted by the yeast in the beer and then literally go on a ‘pub crawl’. They climb into the containers to drink and (slugs not being renown for holding their drink), then drown. There are reviews on the internet which claim this works sometimes and not others and for it to be effective there would probably need to be multiple traps. For me, this being less effective, represents a waste good beer!!..
Nematodes (microscopic worms) are a proven, effective biological control for several garden pests. They work by invading the pest and injecting bacteria into the hosts body. The bacteria multiply, causing blood poisoning and death. The dead tissue is then fed on by the nematode. (Sounds gruesome huh?). As this feeding takes place they also multiply and start seeking new hosts. The good thing is that they are quite specific to the pest (I have used them for vine weevil larvae). The nematodes for slugs are known by the easy to pronounce name of "Phasmarhabditis hermaphrodita" (just rolls off the tongue doesn't it?). These Nematodes aren’t particularly cheap and need to be used carefully. The soil needs to be above 5°c and they need to be mixed with water in specific quantities [Garden organic. 2019].
This application provides around 6 weeks of slug control and is safe for other garden wildlife including bees.
It’s difficult to quantify which method gives the best results and may be a combination of them all, including picking them off by hand. I have also even heard recently on a popular TV gardening programme that slugs are pests that you just have to live with, and general 'garden health' can play a big part in how prolific they become, and there is likely to be some truth in that.
Personally, I’ve been reasonably lucky to not have had too much of a problem with slugs even though I have a liking for Hosta’s in my garden, so I suppose with that statement I'm now tempting fate even by mentioning it.