Garden pests and how to stop them

This week the gardening course went through the various insects and similar life-forms you'll find in the garden and sorted them into lists of friend or foe. The rough rule of thumb we were taught was: fast-moving = friend, slow-moving = foe. So, here's the (completely non-exhaustive) list:

Friends
ground beetles
worms
centipedes
anthrocids
hover flies
lacewings
ladybirds
bees

Foes
caterpillars (and therefore the butterflies that lay them - especially the cabbage white)
snails
slugs
millipedes
aphids (includes black fly and green fly)

Neutral
wasps
earwigs
birds (they pick off insects, but eat your fruit, and pigeons pick at cabbages)

And here are some things you can do to protect your fruit and veg:

1. Encourage/try to avoid killing friendly insects or their larval forms
Many of them eat aphids or other enemy insects.

2. Use netting
7 mm netting will stop butterflies from getting to your veg. I'm pretty sure the netting I used is bigger than that but worked anyhow, but apparently 7 mm is small enough that they definitely can't squeeze their way through, however good your cabbages smell. Here's a cleverer way of putting it over your veg than I came up with (as seen at the allotments):

Netting's also good for keeping birds off your fruit - although I don't always think that's so much of a problem, at least not in London, but maybe it depends on the fruit. At any rate, birds never showed any interest in my raspberries. You can do it just like the picture above - bamboo canes with bottles on the top - or you can build a fruit cage like the picture below. The key thing is don't forget to leave one side of the netting easy to remove so you can get to the plant to pick the fruit.

Here's some insect netting that's sufficiently fine it even stops carrot flies. And better still, unless you are leaving your carrots in for a second year to go to seed they don't actually need to be pollenated, so the fact this also keeps pollinating insects out isn't a problem for carrots, so you cn leave it on as long as you like.

3. Agricultural fleece
This is finer than netting and will also keep your soil and plants a bit warmer (you just roll it out over the top of them), and it's so dense that no insects (or at least not any I know of) can get through. It does let light through though, so your plant can grow under it. The problem is that because no insects can get through, none can get to the plants to pollinate them, so it needs to come off at the point anything needs pollinating. Also, it's probably a bit pricey to just put over everything (although it is reusable).

4. Insect sprays
Obviously it's possible to buy commercially available insect sprays, however, the non-organic ones are not very environmentally friendly and anyway, it's also possible to make your own (which are pretty environmentally friendly). Here are the ones they recommended on the course:

a. Garlic and pepper spray
Kills: ants, caterpillars, cabbage worms
To make: crush garlic, chop/grind chilli peppers. Add boiling water. Allow to cool. Add two tablespoons of pure soap (this seems to mean soap without any added ingredients, presumably either pure liquid soap or pure soap flakes is the easiest sort to use). I assume this recipe is for a spray bottle full, but it doesn't say.

b. Onion spray
Kills: aphids, red spider mites
To make: chop up one large unpeeled onion. Place in a blender with one litre of water and blend on a slow speed to a milky consistency.

c. Soap spray
Kills: most pests
To make: dissolve 225 grams of eco-laundry soap in 9 litres of water. Spray on plants and allow to dry. Hose it down with clean water the next day.

5. Companion planting
The course gave me a list, which I might add to the blog another time, but I've kind of gone off the idea of companion planting after I planted chrysanthemums (which are supposed to deter aphids) next to nasturtiums (which aphids love and which some theories of companion planting say you can plant near other plants that aphids love as a kind of sacrificial plant to draw all the aphids) and this happened:

Nasturtiums absolutely covered in aphids (black fly)

 And worse still, this happened:

Chrysanthemum with aphids (black fly)

My companion plant, the chrysanthemum, which was supposed to deter aphids from all the surrounding plants got aphids itself.

I'll write more about ways of dealing with slugs another time, as it deserves a whole post in its own right.