GARDEN REMEDIES
A smart, ecological garden relies on supporting the ecosystem to keep pests in control with healthy living soil, insects and wildlife such as birds, lizards and frogs.
“When it comes to pests and diseases in the garden, prevention is much better than cure.
”
“A diversity of plants to feed and shelter beneficial insects means they will naturally keep pests in check. ”
SUPPORTING a healthy ecosystem is what sustainable pest management is all about. Like our approach to the human body, when it comes to pests and diseases in the garden prevention is much better than cure. Keeping your immune system – and ecology – healthy is the best approach; far more sustainable, less costly and more guaranteed to succeed than using drastic measures to tackle advanced problems.
Smart gardeners know that healthy soil means healthy plants but soil is only one part of it. An ecology is comprised of an intricately related web of organisms from birds, lizards, frogs, spiders, beetles and preying mantises to microfauna such as worms and microorganisms teaming in the soil such as fungi all working to keep a healthy dynamic balance in an environment. Supporting this means not disturbing the soil and feeding it with mulch, compost and manure from the top like a forest floor while providing a diversity of plants to feed and shelter beneficial insects that will naturally keep pests in check, while nourishing and structuring the soil.
A plant that is continually afflicted, however, is often a signal that it may simply not be in the right position or have the tolerances needed to survive the amount of sun, shade and water it has access to, or the kind of soil it is planted in.
Horticultural chemicals have been the traditional remedy to plant afflictions, but they affect the microbiology of the soil and beneficial insects such as bees, and are believed to be the main reason behind the alarming decline of bee populations around the globe. At an agricultural level, these chemicals have leached into the water table and water bodies causing immense damage. That means using sprays – even organic ones – as a last resort because they will also affect beneficial insects, ensuring our gardens are safe for wildlife, children and pets.
Early detection and action is always best when you’re facing an outbreak. Try and identify what you’re up against (see Resources). Sometimes early acton simply means picking off affected leaves in the case of black spot or scale, or hosing aphids off tender buds. Along with continued monitoring, this goes a long way towards preventing the spread of an outbreak, but even if this occurs a healthy garden will soon produce an outbreak of a specific predator such as Ladybirds.
Prevention relies on working clean: disposing of any diseased plant material off-site (not in the Council’s green waste where it can spread to other gardens), using clean sharp secateurs to avoid tears around cuts that can allow pathogens to enter, and disinfecting secateurs – preferably with methylated spirits – to prevent transferring any potential disease between plants. This approach is simple but effective: monitor, act as early as possible and contain any outbreaks while applying remedies –.the same approach we use for human infectious diseases.
A little knowledge about what you’re up against goes a long way: Planting a variety of plants and interspersing any vegetables among other plants allows the roots of plants to explore different root zones rather than a monoculture where they are all competing for the same resources in the same area as well as masking the scent of juicy vegetable crops that invite predators. Not watering in the afternoon around plants with Powdery Mildew reduces the humidity the fungus thrives in. Apple trees are susceptible to Coddlin Moth and remedies include ringing a trunk with horticultural glue and corrugated cardboard to trap grubs, and planting Nasturtium nearby – a companion planting that is surprisingly effective. Stone fruit are susceptible to a pathogen that causes Gummosis; pruning in summer lessens their vulnerability to viruses entering pruning cuts. Many fruit trees do not need pruning, including Avocado, Mulberry, Citrus and rainforest species, so relying heavily on these species will automatically lower any maintenance and potential issues. Knowledge is half the battle: we recommend picking up a copy of a really good book on pests and weeds that covers what you’re up against in your area. Each region will have different challenges, but we like the US book, ‘What’s wrong with my plant’ and the Australian book, ‘Garden pests, diseases and good bugs’, and urge using these as field guides if they’re relevant to your climate and conditions when you need help with identification and information (see Resources).
And then there’s the field troops: not everyone can do this, but allowing chickens and ducks into a garden for a period of time will efficiently clean up any pests as well as fertilise and ready soil for planting.
As a realistic guide to how often we resort to remedies in a garden over the course of a year, we might use White Oil on any Citrus Miner we come across and cut out any Citrus Gall Wasp we find perhaps once or twice a year, spray off aphids from tender fruit tree shoots and rosebuds with a hose occasionally during spring, and spray Roses with milk a few times over spring and summer. As we only use perennial plants, we avoid many of the pest and disease issues that can plague gardeners using annuals.
Regardless of how you plant, sometimes you just need some ready options to hand – something effective but gentle on the environment – when you find an outbreak late in the process or moving rapidly. The following are some safe methods that have been road tested.
INSECTICIDE SOAP SPRAY
This is US botanist David Deardorff’s organic insecticidal spray. The soap penetrates the cuticle that protects pests and causes cells to collapse. Once the soap dries it is no longer effective and has no residual effect. Use it instead of White Oil if you don’t like an oil residue left on plants.
1 tablespoon liquid soap (such as organic liquid Castille soap)
1 litre water
Mix in a spray bottle and drench pests.
WHITE OIL
Adapted from a recipe by Australian author and blogger Rhonda Hetzel, this home-made White Oil is useful for scale, citrus leaf miner, mealy bug, mites, caterpillars and aphids.
We like to make this in small batches to reduce waste as the oil goes rancid after a few months, indicating that it’s time to make a new batch. There are many recipes for home-made White Oil but we like this one because it uses as little soap as possible (please note that detergent is not soap).
1 cup olive or vegetable oil (preferably organic)
1 tablespoon liquid soap (such as organic liquid Castille soap)
Place ingredients in a labelled glass jar, shake well and store. To use, mix 1 tablespoon of the concentrate in a spray bottle with 1 litre of water and spray on an affected area.
POWDERY MILDEW
Powdery Mildew affects many annuals – particularly Pumpkin and Zucchini, Peas and Cucumbers as well as perennials such as Grape, Tamarillo, Babaco, Paw Paw, Apple and even Roses. Traditional agricultural approaches include sulphur and synthetic fungicides, and in the organic world botanical and mineral oils. However, a CSIRO study found that weekly applications of milk and water at 1:2 on zucchinis was more effective than fungicides. The research also showed that milk sprayed at 1:5 and 1:10 was effective at controlling Powdery Mildew on grapes. Seasonal weather plays a huge role. Powdery Mildew loves humidity with nights around 15C after a warm day. Where we are working has a Mediterranean climate; so by the time that annuals and perennials are succumbing, winter is just around the corner – the time when annuals naturally die off and many perennials such as Babaco and Grape shed their leaves. Spray organic full-fat milk diluted with water at 1:2 on zucchini and 1:10 on grape and other food plants.
BICARB Fungicide
Commercial organic fungicides are largely based on Bicarb Soda. Some botanic gardens in Australia are finding good results using this fungicide on Powdery Mildew, Rust and Black Spot.
2 teaspoons Bicarb Soda
0.5 teaspoon olive or vegetable oil (preferably organic)
0.5 teaspoon liquid soap (such as organic liquid Castille soap)
Add these ingredients to a spray bottle filled with 1 litre of water and shake well before using.
SCALE
Now here’s a fascinating thing: Ants are farmers of scale – deliberately moving them around a tree or even to another plant – as they feed on the sticky honeydew the scale exudes. If you only have a small outbreak of scale, remove them by hand and dispose of it away from your garden. Sooty mold is attracted to the honeydew – and can be easily washed off leaves – but always check for scale, which is the real culprit. Keep monitoring and follow up with a spray of White Oil if warranted.
BLACK SPOT
This particularly afflicts Roses. Pull off any affected leaves as soon as they emerge – without denuding the plant – to stop the spread, disposing of it well away from your garden. If you’ve discovered the Black Spot too late, we’ve had good results with full-strength milk: Put undiluted organic full-fat milk into a spray bottle, spray all surfaces of the affected plant areas and leave to dry. Reapply when the milk has washed off, particularly after rain.
SNAILS
If you’ve ever planted seedlings only to find them completely gone the next morning, you’ll know the havoc that snails can wreak. A fellow Masters classmate was so obsessed by them that he would head out into the garden in the dead of night, especially after a rainfall, armed with a flashlight and pair of chopsticks to drown all the snails he could find in a container of soapy water. Each night’s tally would be gleefully reported the next day. More usual methods include setting out beer in lids to drown the critters and sprinkling a ring of commercial snailbait around seedlings, which works for a while – until it rains and washes away – but it’s nasty stuff for pets and wildlife. We’ve discovered the answer is mulch, lots and lots of scratchy mulch – snails do not like this. We were amazed that after we started seriously mulching to find that snails stayed right away from garden beds. On the very odd occasion that we now find a colony (usually in a quiet dark area like the base of a shady ornamental clumper or at the back of a plant pot), we send the large breeding bull snails flying and leave the rest. We figure they have a right to the garden too, as long as they’re not marauding at will among the food plants, we’re good.
CATERPILLARS
Pick them off and, if they are a huge problem, spray White Oil. Commercial organic growers use the commercial remedy, Dipel, which is organic and uses bacteria as its active ingredient.
CITRUS GALL WASP
Citrus Gall Wasps can puncture the stems of citrus plants to lay their eggs. The first sign you’ll have is that a small section of a branch will be strangely swollen. The only effective remedy we know of is to cut the affected section out and dispose of it well away from your property i.e. not in your compost bin where it can spread to your garden and your neighbours’ gardens. There are commercial wasp traps that are hung from citrus branches that use pheromones to attract wasps to the sticky glued surface, but in our experience the traps also kill a lot of beneficial insects such as bees.
APHIDS
We have found the best way to deal with an attack of aphids is to get to them early and spray them off tender fruit tree shoots and rosebuds with a garden hose. If you let them go unchecked the population can soon swarm a large fruit tree. Even the traditional remedy of using White Oil can’t be sprayed on every leaf surface of a tree, which is why early detection is best. We find that outbreaks of aphids are soon followed by an outbreak of a predator, such as ladybirds.
EARWIGS
This may sound strange, but we once got a call for help about earwigs. We have always thought of earwigs as very useful indeed as they control pests including snails and aphids. However, they also like soft seedlings (although they are nowhere near as voracious as snails when it comes to seedlings) and soft moist hiding places such as Corn silks and Rose blooms. Most organic home gardeners tolerate damage such as small holes in flowers and leaves but protect seedlings with cloches or set out lids with beer or oil to attract and drown any marauders. Unless you’re in the business of producing lots of seedlings, we think their benefits far outweigh their damage. And children are fascinated by them.
A WORD ABOUT WEEDS
Weeds can be easily suppressed by continuous mulching and dense planting that out-competes them. If a stray weed does sprout in your garden that you do not want, get rid of the weed before it seeds and do not dispose of the seeds in your compost or garden.
There’s one weed, however, that needs special attention because it can sometimes outwit these methods. There are several varieties of Oxalis with some of the most aggressive varieties completely carpeting State Parks and rivers. The despair of many gardeners, Oxalis spreads by bulbs that are dispersed by disturbance, which is why it is recommended that careful removal by hand be carried out when the plant is exhausted and in dormancy. Glyphosate – commercially known as Roundup – has been the traditional answer to Oxalis. However, many are taking notice of current US court cases in which defendants have won against Roundup’s parent company Monsanto, now owned by pharmaceutical giant Bayer. Class actions are being prepared in the US and Australia while the World Health Organisation has banned Glyphosate as a known carcinogen. In Australia most local councils are still using the weed killer, although they are slowly shifting to using steam to deal with weeds.
Traditionally, home gardeners covered Oxlis outbreaks with newspaper for a few seasons. In the organic realm, sites affected with Oxalis are usually tarped with black plastic and left for more than a year to starve the plants and destroy the bulbs. If you have Oxalis in an established garden and cannot tarp areas with black plastic for extended periods, try using heat by experimenting with repeated applications of boiling water on Oxalis leaves. The idea is to kill the leaves, which photosynthesise and feed the plant. By repeatedly destroying the leaves as they emerge, the bulb will eventually die. Using heat on Oxalis leaves can also come in the form of fire. We are experimenting at the moment with the Hot Devil propane wand after favourable reports of gardeners using it to deal successfully with Oxalis. Stay tuned.
Other weeds in the garden, such as Nettle, Dandelion, Chickweed and Dock, are valuable and nutritious wild foods and a smart gardener encourages these as part of their edible garden. Although Oxalis is invasive, it is also edible and delicious, and can be used as a wild food plant – if you can keep it contained.
“Weeds can be easily suppressed by continuous mulching and dense planting.”
“Weeds ... such as Nettle, Dandelion, Chickweed and Doc are valuable and nutritious wild foods and a smart gardener encourages these as part of their edible garden.”
RESOURCES
Denis Crawford, 2015, Garden pests, diseases and good bugs: the ultimate illustrated guide for Australian gardeners, HarperCollins.
David Deardorff and Kathryn Wadsworth, 2009, What’s wrong with my plant?: A visual guide to easy diagnosis and organic remedies, Timber,
Adam Grubb and Annie Raser Rowland, 2012, The Weed Forager's Handbook: A Guide to Edible and Medicinal Weeds in Australia, Hyland House.