Meet Your Garden Life:
Organic Pest Control and Adventures in the Backyard
Microcosmos (Course Notes)
There are an estimated 10 quadrillion (10 million billion) micro-organisms living in a suburban
organic backyard, and many tens of thousands of insects and other arthropods, and we'll often find
birds, lizards, bats and marsupials. Beneath our feet, in the air, the water and the undergrowth are
dramas and wonders, often unseen and unappreciated. Many pest problems are caused by an
imbalance – and attempting to destroy the pests can lead to further problems. In permaculture we
encourage observation, understanding, and introducing more life rather than removing it wherever
possible.
Soil life
Soil is a living ecosystem. The more biodiverse and biologically active your soil, the healthier are
your plants. The healthier your plants, the less disease and the less pest problems you have.
A good gram of organic garden soil has many billions of organisms in it. Plants pump exudates of
sugars, other simple carbohydrates, and proteins (AKA 'cakes and cookies') into the soil to feed soil
life. Plants need soil life. Microbes create humus and good soil structure, breakdown organic
matter and cycle nutrients, provide disease protection to the plants, and form some symbiotic
relationships for the access of nutrients.
Bacteria: The most populous creatures in the
soil. Bacteria, although single celled have far
more chemical tricks than 'more evolved'
creatures such as ourselves or plants. They can
exchange DNA like trading cards between each
other to find solutions to novel chemical
challenges very quickly. The glue bacteria create
in order to stick themselves to soil particles is
important for creating soil structure. Certain
bacteria collaborate with legumes to capture
atmospheric nitrogen.
Fungi: Underneath the soil lie vast networks of
interconnected fungal hyphae (strands). Fungi
are especially adept at breaking down woody
material and accessing nutrients from rocks.
Micorrhizal fungi have a complex chemical
language with plants and exchange nutrients for
'cakes and cookies'.
Protozoa: The larger single celled organisms:
amoeba, cilliates and flagellates are the main
predators of bacteria and fungi, and are vital for
nutrient cycling.
Nematodes: These microscopic worms are also
bacteria and fungi predators. Some types also
attack plants such as tomatoes, however rich and
diverse soil biology mitigates this.
Arthropods: Springtails, mites, and insects and
their larvae inhabit the soil. They cycle nutrients,
create soil structure with their fecal pellets, and
are 'taxi cabs' of the soil, moving bacteria and
fungal spores around.
Earthworms: According to some calculations,
earthworms collectively provide the earth turning
capacity of five horses per acre in earthworm rich
soil. However they do this in a way which
improves soil structure, not destroys it. They
aerate the soil with their burrows, breakdown
organic matter and introduce excellent soil
biology in their castings.
Soil strategies:
Like you, your soil needs air, water, shelter and a balanced diet.
Compost and mulch: Well made compost is a hothouse of healthy soil life. Compost introduces
both the life and humus needed to maintain that life in the soil. Humus creates good soil structure
which allows air and water to penetrate, provides habitat for soil microbes, and is a medium for
nutrients to be stored. See the VeryEdibleGardens.com iVEG page on compost, or come to one of
our Compost and Worms courses to learn how to achieve a balanced diet and make a good compost.
Harsh winds dry the soil while direct sun kills exposed microbial life. Mulch provides both shelter
for the soil, temperature control, and food for the microbes who eventually turn that too into humus.
Aerobic vs anaerobic life: The type of organisms congenial to good plant growth are aerobic – ie.
those that live in oxygen rich environments. Good aerobic compost actually kills human and many
plant pathogens. Make sure your compost is well aerated using strategies such as drilling holes in
your compost bin, adding at least as much carbonous material such as straw or cardboard as food
scraps to your pile, turning the pile with a fork or compost screw. Don't use too much water on
either your soil or compost – they should be moist, not soaking – and don't walk on, or regularly dig
your garden soil, to maintain good structure so air can get in, and water can drain.
Fungi to bacteria ratios: Trees and other perennials prefer fungi dominated soils, whereas vegies
prefer bacteria dominated soils. Increase the woodiness of your mulch or carbon level of your
compost to encourage more fungi, and lower it to encourage more bacteria. So use wood mulch for
trees, straw for vegies.
Common garden insects:
Aphids: A common garden pest across many species of plants.
Aphids can reproduce asexually and build populations rapidly.
Are sometimes 'farmed' and protected by ants, who eat their
sugary secretions. Predators include parasitic wasps, hoverfly
larvae, lacewing larvae, ladybirds and spiders. Can be hosed off
with a strong get of water. As a last resort can be controlled by
garlic spray, white oil, pyrethrum spray and others.
Whitefly: Can be a serious sap sucking garden pests. You'll see
clouds of tiny white moth like insects when they are disturbed.
They can cause a yellow mottling of the leaf, spread diseases,
and invite fungal attack. Most aphid predators are also whitefly
predators. Some people vacuum them off with a portable
vacuum on cold morning when they are slow. Sprays which
work on aphids generally work on the closely related whitefly.
Scale: Although it doesn't look like it, scale is also an insect, one
related to whitefly and aphids, which however loses
functionality of its legs in adulthood and forms a shell. A
problem of citrus trees and some other trees, not vegetables.
Whiteoil can control it, if it seems to be out of control.
Cabbage white butterfly: Attracted to everything in the
cabbage family, it's important to control the caterpillars,
especially when plants are young. Natural predators include
small birds and parasitic wasps. Physically pick off the
caterpillars, and rub off the tiny eggs. BT sold as Dipel and
other products is a bacteria based spray which attacks only
caterpillars.
Ladybirds: One of the gardener's best friends, the ladybird and
it's larvae (pictured) are voracious hunters of aphics, whitefly,
small caterpillars and other garden pests. They aren't active in
cold weather, but where aphids are found they are usually quick
to follow, especially if you provide the right flowers to attract
them (see below).
Parasitic wasps: These tiny wasps are ubiquitous, but so small
that you have to look for them. Different species are adapted to
different garden pests, including aphids, whitefly, caterpillars.
Some even attack other parasitic wasps! They like the same
kind of flowers as ladybirds (see below). Look out for the hard
brown shelled aphids – they have been infected by the wasp
larvae. They are tiny and harmless to humans.
Hoverflies: These small flies with bee like markings eat mostly
pollen, however their larval offspring love to chew through
aphids and other small pests. They like the same kind of flowers
as parasitic wasps and ladybirds. This one is on a calendula.
Praying mantises: Incredibly strong predators, they eat
anything and everything (including other predators). They are
elegant and lovely to watch, and good guys in the garden.
Common garden macro-fauna:
Spiders: No insect predators do more work than spiders. Some
are free ranging hunters, some make webs. Few are dangerous
to humans, so try to learn to love them.
Snails and slugs: If young seedlings are going missing
overnight, or large holes appearing like those pictured, the
culprit is likely slugs and snails. They generally only come out
at night. You may find their slime trails. Some birds, frogs,
lizards and rodents are predators. Chickens love them, and
having a chicken run near the vegie bed seems to offer some
control. Beer or sugar water placed in a bowl and buried to soil
level is an effective trap. Start putting them out a few nights
before planting to clear populations first. Coffee grounds can
provide a physical barrier.
Centipedes, millipedes and slaters: These many legged
arthropods perform different roles in the garden. Centipedes
(pictured) are predators. Millipedes and slaters generally eat
decaying organic matter. Slaters sometimes eat seedlings but
are generally not a problem.
General garden strategies:
Start with the soil, as healthy soil allows plants to have strong immune systems.
To attract predator insects such as ladybirds, hoverflies and parasitic wasps, the following types of
flowers are useful:
● Umbelliferous plant flowers. This includes carrot, dill, fennel, parsley and others
● Daisy family
● Marigold family including calendula
● Alyssum
Providing water for predators in the form of a small pond is useful. Put rocks around to provide
habitat for frogs and lizards.
Provide habitat for small birds with dense native plants. Grevilias, fuscias and banksias bring in
honey eaters and wattlebirds which also eat insects.
Look for predators before spraying. If they are present, allow that plant to stay, even if sick, so that
the predators may breed up in numbers.
Observe insects and try to exclude pests.
As a last resort, you can make your own organic sprays using ingredients such as potassium soap
(available from nurseries) or oil and water to smother and suffocate insects. Herbal infusions of
garlic, chilli, wormwood, tomato leaf and many others help with various pests.
Our favourite organic pest control book is the 2010 release Bug by Tim Marshall (see below).
Here's Tim's quick garlic spray recipe:
Garlic spray recipe
To make a large quantity of garlic spray, follow this recipe:
500g crushed garlic
150-200mls liquid paraffin (just enough to cover garlic)
2.5L water
150g pure soap
• Soak the garlic and paraffin together for 24-48 hours
• Add remaining ingredients and stir thoroughly
• Filter the mixture well (a commercial filter or sieve is best, but a piece of muslin or tea towel
will suffice).
• Store in a glass container (flagon bottles or jars are excellent), away from sunlight.
• Dilute at the rate of 15-30mls of concentrate per 1L of water, depending on use.
Resources
iVEG: Our growing source of organic gardening fact sheets. www.veryediblegardens.com/iveg
Green Harvest: Organic gardening supplies and a great information source on common garden
pests: www.greenharvest.com.au
Soil Foodweb Institute: For analysis and information about soil biology:
www.soilfoodweb.com.au
Books
●
Organic Gardening by Peter Bennett includes an excellent introduction to the common life
in your garden. Available through www.veryediblegardens.com
●
Bug: The Ultimate Gardener's Guide to Organic Pest Control by Tim Marshall – absolutely
great Aussie organic pest control book, recommended by Peter Cundall
●
Insects and Gardens: In Pursuit of a Garden Ecology by Eric Grissell is US based but a fun
and involving read about backyard ecosystems with a focus on insects.
●
Teaming with Microbes by Jeff Lowenfels and Wayne Lewis is a gardeners' introduction to
the life of the soil.
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