Pest Control in a Wildlife-Friendly Organic Garden

 It can be disheartening to see your ripe strawberries half-eaten, your green lettuces reduced to a barely-recognizable stump, your potatoes hollowed out by underground miners, and your spinach leaves riddled with small and large teeth-marked holes. While you could reach for those bottles of agrochemicals, carefully laid out at the garden centre (you can smell them from quite a distance), there is an alternative way. Gardening organically will encourage wildlife into your green space and help you keep the pest population under control.

The Organic Gardener has several tools in her or his toolbox:

Prevent pests entering the garden

This basically means knowing where your plants and growing media come from. Buying from an established commercial nursery/garden centre should be fine. Buying a plant, donated by persons or persons unknown, at the local village fete is higher risk but may still be worthwhile. Growing from seed is probably the safest but healthy-looking plants should be fine. I would always recommend using certified seed potatoes, rather than a bag of potatoes bought at the supermarket, because this vegetable is susceptible to more than its fair share of pests and diseases that will live in the soil for many seasons. Slightly contrary to this advice, planting garlic cloves bought from a supermarket is relatively low risk because garlic comes equipped with its own pest control.

I'm sure I don't need to remind everyone that it was, essentially, poor monitoring and control of imported trees that led to the extremely serious Ash dieback fungal disease that is now devastating the UK tree population. This was not the first imported disaster and will not be the last.

I don't use animal manure to fertilize the garden because I prefer to make my own plant-based compost. If you want to use manure beware that it can contain a whole suite of weed seeds - some of which are difficult to get rid of once they've established themselves in the garden - and there can also be a problem with weedkiller chemicals in manure. Manure from ruminants (cows, sheep) is likely to contain fewer seeds (c.f. horse manure) and hot composting will reduce the weed seed population to acceptable levels. So make sure you know where the manure has come from and how it has been processed unless you are going to hot compost it yourself.

Barrier Defences

Hosta Halo - Slug Barrier

Here we are talking about physical barriers placed between the pest and the plant. The Hosta Halo (aka Slug Collar) is a good example - its shape makes it difficult for the slug/snail to cross and I find then very effective. Various other slug barriers are available or can be prepared at home (e.g. copper tape, strawberry mats, sheep's wool, egg shells, wood ashes, coffee grounds, diatomaceous earth). I think it is difficult to beat the Hosta Haloes for value as they will last many years (mine are 10 years old and still working!) and can be moved on to protect another plant once the first plant has grown sufficiently to be able to resist a slug attack. Maybe different colours (especially brown) would be useful if you want to hide them in the flower garden.

Here garden fleece is used to protect my strawberry crop...

Before

...from hungry birds, especially blackbirds. Without protection, I could easily lose half my crop. The fleece is held on by strong bulldog clips (easy removal for watering, feeding and picking) and can be dispensed with once cropping has finished...

After

Garden fleece finds many protective uses in the kitchen garden. It can be used as frost protection but here it offers barrier protection against onion fly...

Fleece Barrier against Onion Fly

 A similar system can be used against carrot fly but this is not a crop I usually grow as they don't do particularly well in my soil.

Fruit/vegetable cages are another form of barrier protection. The netting comes in a variety of mesh sizes depending on the type of protection needed. I use a butterfly-proof size to protect my brassicas from the cabbage white butterflies and pigeons. Also my climbing french beans/mangetout need early protection from birds as they enjoy the young flower buds and retard the crop - the netting is raised or removed once the plants are well-established).

Fruit/Vegetable Cages

Other forms of barrier protection are available on an 'as needed' basis: for example, brassica collars to protect against cabbage root fly, rabbit/deer fencing, ultrasonic devices to deter moles, cats, dogs.

Glue bands  offer barrier protection for fruit trees to deny crawling insects (winter moths, ants, vineweevil, earwigs, etc) access to the upper parts of the tree...

Glue Band Protection on Pear Tree

   

Finally, don't forget the virtual barrier of crop rotation, especially in the kitchen garden. This helps prevent the build-up of crop-specific pests and diseases in the soil. Usually a 3- or 4-year rotation system is employed - I use the latter. On a similar note, try not to replant perennials (mainly fruit in the kitchen garden) in the same location if possible - although this is tricky for small town gardens with limited space.

Encouraging Friendly Wildlife into the Garden

While, clearly, certain wildlife (i.e. pests and diseases) is not welcome in the garden, you might want to invite other forms of wildlife to enjoy the garden with you. Not only does this make life infinitely more interesting but it can also help you control some of those pests and diseases feasting on your crops and flowers.

The simplest and easiest way to do this is to put up a bird feeder...

Finches Friend Bird Feeder

...there is a huge variety to choose from to provide our feathered friends with seed, mealworms, peanuts, etc. Do not put out bread as this is neither nutritious nor healthy for the birds. We have recently invested in a Finches Friend bird feeder which has a capacity of nearly 3 litres and an easily removable feeder station for cleaning; it comes with a spare feeder station so the birds do not have to interupt their feeding! It is on the expensive side but will hopefully last for many years. So far, it has proved very popular with the smaller birds: robin, blue tit, great tit and sparrows are regular visitors. The easy cleaning part is important because diseases such as Trichomonosis are devastating some bird populations. Whatever bird feeder you use, make sure it is regularly cleaned, disinfected (& rinsed) and dried; say, once a week.

Why do we invite birds into the garden? Because they like to eat a variety of insects, some of which you would classify as pests. We have a resident sparrow commune that lives in the ivy hedge you can just see in the photo below...

One of many local sparrows

The sparrows are very efficient at controlling the local aphid population. Other birds will happily eat caterpillars, slugs, snails, grubs and other pests. There is a downside because the birds will also happily gorge on your strawberries and cherries which is why you need barrier protection (see above) when these fruits are ripening. To attract blackbirds and robins, just leave a bare patch of earth - it helps to dig it over occasionally - where they can hunt for worms, beetles, and grubs.

If you have room for a pond, no matter how small, you may be able to encourage frogs & toads to take up residence. These amphibians eat snails and slugs, woodlice, beetles and bugs - toads have a fondness for ants, apparently.

You can also entice wildlife into the garden by providing food (e.g. flowers to attract bees, butterflies and insects) and shelter (hedgehog houses, bee/lacewing/insect hotels). Make sure your garden allows access for mammals such as hedgehogs and they will repay you by eating your slugs and snails while you sleep in your bed.

Leave a wild area containing wood piles, leaf litter, weeds, and bare soil to attract everything from worms and insects to birds and mammals. Not everywhere in the garden needs to be tidy!

Of course, it goes without saying you should avoid using pesticides and herbicides, including metaldehyde slug pellets, as these are definitely wildlife-unfriendly.

Biological Control

This form of pest control has exploded in recent times as more and more products aimed at specific pests have been made available to the amateur gardener. I use Nemaslug twice a year to keep the slug/snail population in check during the critical time when vegetable plants are getting established (late Spring/early Summer).

Biological methods can be quite expensive so you need to target application to the most troublesome pests. I have very limited experience of their use apart from the use of Nemaslug. Vine weevil is a particular problem we have with our container plants. I have tried the nematode route but I cannot confirm unequivocally that it was successful (unlike Nemaslug) - it certainly did not eradicate them but it may have reduced their numbers.

To control codling moth (apples and pears) and plum fruit moth in the orchard, I use sticky traps baited with pheromones...

Codling Moth Trap

Two 'applications' are needed to cover the critical May, June & July period when protection is needed.

Under this heading, you could include sacrificial  and companion plants; the former draws pests/diseases away from your favoured plants (i.e. sacrifices itself for the good of the favoured plant) while the latter confers some benefit to the favoured plant (e.g. by improving its vigour, sacrificing itself or detering pests).

Catching and Disposing of Pests

Probably not everyone's cup of tea but physically catching and disposing of the little critters is an option for certain pests.

Slugs and snails are easy to spot and catch - you can use a trowel or wear gloves if the thought of touching them is unpleasant - and this can be done while you are doing other things in the garden. Some people suggest going on nighttime searches with a torch - generally, I have better things to do with my time!

We dispose of our catch in our hot composter bins - the 60 ℃ temperatures make short shrift of them. It may be an urban myth that slugs and snails have a homing instinct so just throwing them into your neighbours' garden may not work and is certainly not neighbourly. Crushing underfoot may be the quickest form of death but it does leave a mess and the residue is surprisingly slippy so be careful you don't slip. Other suggested disposal routes include hot or salty water.

One step away from actually capturing the slugs/snails yourself is to use slug traps filled with some liquid attractant (such as beer or commercial baits) in which the slugs/snails drown (or do they?). There are some opposing views on how effective slug traps are, whether they attract all slug-types, what is the best attractant and how the slug actually dies. Cheap and easy (albeit a little messy to dispose of) and of doubtful efficacy. Some slugs are attracted and die in the traps but some slugs just have a drink and move on (a sort of sluggish pub crawl).

The only other pests we routinely 'catch' are lily beetles and vine weevil grubs (when emptying/repotting containers). These are disposed of underfoot or added to the hot composter bins. A jet of water applied from a hosepipe or pressurized sprayer will dislodge blackfly on broad beans and prevent them overwhelming the bean plant - no catching or disposal in this case!

Wildlife-Friendly Chemical Control

Use of chemicals, even environmentally-friendly chemicals, should be always be a last resort. Nevertheless, there are times when they do need to be used. First and foremost, wash and sterilize pots, trays and equipment to prevent passing on pest and diseases.

For pots and trays, I set up a temporary washing station to remove excess soil with a hosepipe...

Wash Station

...the waste water is used in the garden - usually on the nearby fruit and pear trees. The washed pots are then taken to the temporary disinfectant station...

Disinfectant Station

...where they are scrubbed and soaked (for at least 30 minutes) in a 1:150 solution of Citrox P before drying and storage. Tools and other items can be similarly treated or sprayed with the dilute Citrox P solution.

I always have a bottle of ferrous sulfate pellets or spray (Grazers Slugs & Snails) to hand to deter slugs when Hosta Haloes and/or Nemaslug treatment is not available or impractical. These slug pellets are non-toxic to other animals and just as effective as the old metaldehyde ones which are now banned.

Last year I bought a bottle of Grazer's Red Lily Beetle spray. Combined with search and destroy, this does seem to have reduced numbers this year although I cannot say whether either or both options were responsible.

For pest and diseases in the garden such as whitefly, aphids, wooly aphids, mealy bug and fungal diseases such as mildew, I use SB Invigorator concentrate made up into a spray. This is an effective if temporary means of pest/disease control so regular application is needed. Basically, if you have an infestation, this is a reasonable choice for a first attempt.

The final 'chemical' intervention in my arsenal, are garlic greenhouse candles. I fumigate the polytunnel and greenhouse in winter/early spring to clear out any unwanted pests. They can even be used when the greenhouse is full of plants, unlike their sulfur-based predecessors, should you be unfortunate to suffer a severe infestation of red spder mite, whitefly, aphids or other pests during the growing season.

This post has turned out to be much longer than I expected but hopefully will be of some use. If I have forgotten something, I will add it at a later date.