Suddenly, a public health crisis has prompted more people than ever before to spend more time growing food than ever. We live in a nation of garden cities and our food gardens are an open invitation to dine; what could possibly go wrong? Keeping pests and diseases firmly in their place involves safer solutions, a little gentle manipulation and gardening and learning together as a family.
Suggested listening to accompany this blog: ‘The Extraordinary Garden’ by Charles Trenet.
NOTE: my blogs and social media posts contain hyperlinks for further information. If you don’t use them, you’re merely scratching the surface…
Instant information is not necessarily wisdom
The internet abounds with instant information, but not necessarily wisdom. If someone is trying to sell you their product, they may put profit first. That’s why you can trust public organisations like the Australian Broadcasting Corporation’s Gardening Australia and the BBC’s Gardeners’ World – these programmes have no commercial loyalties.
Do you rely on a web-based gardening know-how site? Is the information relevant to the southern hemisphere, or the northern? This website and my Public Facebook page are followed in 109 countries. The Seed Saver’s Network is connected to more than 100 other seed saver organisations. I answer 9,000 to 10,000 gardening questions each year. Often, this involves soothing gardeners made anxious by gardening know-how sites about pests or diseases that aren’t active at that season or in their climate zone. Sometimes they aren’t even present in their country.
Whether you’re a fruit farmer in England, a market gardener in Thailand, or a home gardener in Brisbane, we all need economical, effective solutions to protect our food supply and within budget. And that’s the kind of practical advice I’ve been providing for over thirty years. Step into my world…
Gardening in the real world
Wherever you garden, and however skilled you are, we all face the same dilemma when a well-tended crop is threatened by pests. Do you intervene? How?
Perfection does not exist in nature or in a garden. What would a scribbly gum be without its scribbles? Whenever you see a perfect, blemish free fruit or vegetable in a supermarket, the question you need to ask is – what chemical solution created this unnatural state? And what impact is that chemical having on soil health, crop nutrition and my food? This is where I put on my hat as patron of the National Toxics Network, an expert organisation with global reach and which is committed to food and environmental safety. If the world placed as much importance on sustainable food production as it is on coronavirus, I’d be permanently unemployed. Whatever the price tag says on conventionally grown food, the hidden cost to the environment is usually pollution.
Expect caterpillar damage
I live in a very ordinary suburb in subtropical Brisbane. Wynnum lacks national parks, it’s throughly developed and yet I have recorded over five hundred species of animal that live in or visit my food garden. Even ordinary Australian suburbs are clearly teeming with life. By keeping a list of garden animals and discovering which are allies, which are enemies, and which are simply biodiversity, I can now reassure beginner gardeners that most species are harmless, that more species actively assist food production than harm it, and just a few require seasonal control.
For example, during seventeen years of gardening here, only ten out of the 75 species of butterfly and moth can be nuisances some of the time. The rest are fluttering confetti. Eye candy!
Of the ten species requiring some action, only one, the cabbage white butterfly, is an all year round potential threat to crops in the cabbage family (Brassicaceae). So, in summer I don’t grow any of its food plants as there’s always a surplus of other seasonal crops to eat. In my next blog I will introduce you a native biocontrol that helps control this pest butterfly.
Avoidance is my favourite method of not dealing with caterpillar attack. I’m lazy! By sowing Asian greens, like Chinese cabbage, in late autumn and growing them through winter, the time when moths that pester them have a pause in breeding, I can sneak in a crop of over 100 kg of Chinese cabbage from a ten square metre plot with little worry. Crafty!
At other times of the year, simply draping fine mesh (old net curtains with fine mesh bought from a charity shop will do) over rows of Asian greens and salad vegetables prevents moths and butterflies from being able to lay eggs. Simple!
Spraying natural, cold-pressed neem oil (at the recommended rate) over leafy greens, like kale and broccoli, deters egg laying. In Australia there is only once source, more of that in my next blog. Use neem and discover how prevention is better than cure. Devious!
In Queensland, there are two bothersome grasshopper species that frustrate gardeners most of the year. As with moths and butterflies, exclusion mesh works. In my garden, grasshoppers use sweetpotato as their nurseries, they love their leaves and it’s not possible for me to net them.
Early in the morning or at dusk, grashoopers become less active so it’s easier to swat them with a trowel. Wallop! You can also slowly approach them from behind with a pair of secateurs and behead them. Snip! Spot spraying, using pyrethrum, is another way you can knobble them when they are out of reach.
My grandfather had the best remedy for both caterpillars and grasshoppers. By spraying molasses, you control the pests while improving crop health. If you don’t have money to burn, buy molasses in bulk from a produce store or pet store, not a supermarket.
Working in the background are mantids, hunting insects which feed ferociously on a range of insects, including caterpillars and the biggest of grasshoppers. Six species of mantid live and breed in my garden. How many live in yours? In summer they hunt 24/7; grasshoppers cannot rest in peace even at night. Learn to recognise mantid egg masses and protect them. A mass hatching of mantids is quite a spectacle. Observe!
Rats and mice are always around, especially if you keep pets and poultry. Do not leave food bowls outside. Clean them before re-use. Where possible, avoid poison baits. Dying vermin, poisoned by baits, attract beneficial animals like owls and frogmouths as they struggle. Don’t poison your vermin patrol.
In my garden, tall bamboo wigwams provide perfect perches for these nocturnal hunters. Dead branches on trees also serve a similar role in pest control, so only prune them off for safety reasons. A branch may be dead but it’s still helping to control vermin.
Indoors, I use an old-fashioned meat safe to store fresh and ripening food. Leaving tomatoes and bananas out at night will entice vermin to make night raids.
Recently, I recorded a story on various methods of non-chemical methods of vermin control for television.
Scrub turkey trouble?
I count myself lucky that my garden is unaffected by these native birds. I recorded a story on how understanding their behaviour can keep a gardener one step ahead of them. I’ve also written a blog which gives you even more ideas how to live with these successful colonisers of our suburbs.
Possums, birds, lizards, snakes…and vermin again
Exclusion is the best solution. Possums and birds can be prevented from harming crops by using net curtains, shade cloth, wire mesh or fruit cages. Friends in Western Australia’s wheatbelt grew all their food – grapes, citrus, herbs and vegetables – inside a ‘maximum security’ enclosure made from chicken wire. It’s possible to have wire mesh enclosures made to order to fit into smaller gardens and tight spaces.
These farming friends also had a smaller, separate setup to prevent foxes, monitor lizards, snakes and vermin from harming their poultry. In this case, chicken wire from the fence is buried 15cm deep below the surrounding soil level and a section is laid flat to extend 1 metre out and away from the base of the enclosure. Foxes and lizards go to the base of the fence to dig down, they don’t step back and then tunnel underneath. Stymied!
My garden isn’t enclosed. In winter, possums want to eat juvenile jackfruit, all the leaves from my chocolate pudding tree, jaboticaba and cassava. Raw cassava leaves are laced with cyanide, which gives you an idea of the iron constitution of a possum. Possums access these trees by walking along the fence, safely out of reach from dogs, and you can see where they spend most of their time because their claws wear off the paint. This is precisely where I smear menthol. Weekly applications during winter keeps the possums moving. It tastes foul.
The most effective general purpose possum deterrent is chilli spray, but pick your chilli wisely – if it isn’t atomic, don’t expect it to work 🙂
A word about pantyhose
You can buy fruit protection bags to wrap around individual fruit to keep possums at bay. And you can make your own bags from old net curtains or shade cloth if you can sew.
I use old stockings. I wouldn’t have had a great crop of jackfruit this year without up-cycling old pantyhose to enclose each fruit. Pantyhose is very useful in the garden for a variety of purposes, it stretches beautifully without harming swelling jackfruit. And it was a gift.
Basic ecology: sooty mould, ants and sap-sucking pests
This is not a serious problem, but it causes dismay among unconfident gardeners every year. On a couple of occasions in Queensland I’ve seen an entire garden blackened by it.
Sooty mould involves a basic ecology, the interaction between a fungus, a pest, an ant, a host plant and a gardener. Sooty mould spores are present in the air. If some lands on a source of food, usually on a leaf, it germinates and spreads. It may eventually coat a plant, turning it black. This is a visual cue that somewhere above the mould is a thriving colony of a sap-sucking pest which is probably being farmed by ants.
Ants diligently farm sap-sucking pests, especially during drought. What they seek are well watered plants that have been given lots of nitrogen fertiliser. This combination helps plants to grow fast, produce lots of carbohydrate and it increases sap flow – paradise for a sap-sucking pest. Ants farm aphids, mealybug or scale insects because they all excrete honeydew – excess sap – and this is what ants gather from them. Ants carry these pests to colonise fresh plants to increase honeydew production. Honeydew is sugar-rich food, and any which is uneaten usually falls onto foliage below where it becomes food for sooty mould. As this mould grows it turns foliage black. Sooty mould is unsightly, it stops leaves producing energy, but it can easily be wiped off with a soft damp cloth and soapy water.
Spraying affected plants with commercial horticultural oil three times with three weeks between each application will control sap-sucking pests, the source of the problem. Spraying oils like white oil, Pest Oil, DC Tron and Synertrol are suffocants, not poisons, and they only kill what they smother. If after three applications the pests remain, it’s probably because you haven’t thoroughly coated all the leaf surfaces (top and bottom), all the stems and the bark right down to the soil. Spray very early in the morning and don’t rush it.
I use the same method to control major infestations of caterpillars – like the cluster caterpillar that attacks my gac vines (Momordica cochinchinensis) and banana in summer.
Control the sap sucking pests, and the sooty mould dies and it gradually crumbles away. And the ants will move on and look for another sappy plant that’s overfed with nitrogen. Nitrogen is vital for healthy plants but remember that just because a little is good it doesn’t mean that a lot is wonderful.
Tomatoes, a favourite fruit
The ideal temperature for tomato production is 23C, so in the coastal tropics and subtropics the best time to sow or plant tomatoes is during March. Something routinely ignored by popular gardening magazines that think Australians only garden in Melbourne.
Avoid wetting tomato foliage at all times. Tomatoes easily succumb to many problems, and since wet foliage encourages disease, it’s better to avoid foliar feeding as well. Water or apply liquid feeds to tomatoes directly around the roots.
I find that by watering tomatoes on alternate days during dry weather the rhythmic application reduces the risk of two common problems: fruit splitting – caused by irregular and uneven soil moisture – and attack by root knot nematode, caused by consistently damp, warm soil and made worse by failing to rotate crops.
How can watering influence successful pest and disease control?
You can’t stop rain (unless you have an overhanging roof, a glasshouse or polythene igloo), but you can control how and when you water. It is vital to protect some crops, like tomato, chilli, capsicum and eggplant from being damp overnight.
Leaves that have a film of moisture on them overnight may activate bacteria decay and fungal spores so they can penetrate the plant and spread infection. Rust, mildew, canker, there’s a long list of rotten problem that can be avoided by watering early in the day and allowing foliage to dry out.
Suggested listening to complete reading this blog: ‘La Mer’ by Charles Trenet.
Gardening as a family
Everyone starts gardening sometime. I started when I was four. My grandmother supervised me as I dug the soil and raked it level. She showed me how to carefully scatter the seed of radish, lettuce and spring onions, to rake the seed gently into the surface, and to gently water them in. She instructed me to check them for watering every morning before breakfast (“you only get breakfast when everything else has had theirs”) still a habit today. It was fascinating observing my first crops germinating.
A week later, she introduced me to snail bait. In Australia, organic-approved Multiguard Snail Bait is child, pet and wildlife safe. She showed me how little you need to protect seedlings.
An alternative way to control these pests is preparing espresso coffee and diluting it with water: one part espresso to five parts water. Spray this on seedlings and the surrounding soil. Re-apply after rain or watering. Caffeine is an effective molluscicide.
Make hand watering a family activity. Hand watering is very useful, because the time you spend watering gives you time to observe change. What has happened since you last watered? Spot weeds and remove them before they set seed. Save time weeding. Is that a sick leaf? Turn it over and see if there’s a pest lurking underneath. Removing a single sick or pest-infested leaf may prevent a problem spreading to a whole plant. Save time on problem solving.
Watering can become a valuable lesson in garden ecology. Take a camera with you. Photograph any insect you spot but don’t recognise. Work out if it is a friend, an enemy, or simply biodiversity. You may even discover a new species.
My Public Facebook page has a photo album called ‘Curious Garden Creatures‘ with images of over 500 common garden animals with notes, comments by gardeners and hyperlinks that take you to further reading. Don’t know what they are? Ask an expert at your state museum. You might even discover a new record or better still, a new species undescribed by science. Technology has reached the point where every gardener can be a scientist.
It’s reassuring to know that in a complicated world, even simple tasks, like watering, can help to keep pests and diseases firmly in their place and that good gardening solutions are safe.
Real life is never portrayed on the glossy front cover of a gardening magazine
Like real life, sustainable gardening involves getting a few bumps and bruises along the way.
My gardening hero and organic gardening pioneer, Peter Cundall, often remarks that gardeners are on a lifelong journey of self-improvement and the more you practise, the better the results.
Earlier this month, I spoke with Pete on his 93rd birthday and he told me what a good year it had been for fruit and potatoes. He’d had an amazing glut of tomatoes, nashi pear and plums. He’d grown such an embarrassment of produce he keeps putting his surplus out by the front gate with a sign inviting people to ‘take what you need’.
Sustainable gardening means heavy crops of nutritious food and a healthier environment. The sooner you start, the better you become. Everyone and everything wins.
In my next blog I’ll look at the essential organic products I keep to hand in my garden cupboard, plus a compendium of sustainable solutions.
Happy gardening 🙂
Director, Seed Savers’ Network Inc.
Patron, National Toxics Network Inc.
Patron, Householder’s Options for Protecting the Environment Inc.
15th April 2020
3 Comments Add yours
So much food for thought, and so delightful! I will need to read this more than once and keep coming back to it. Not just solutions for pests and diseases of the plant world, your writing (in combination with getting our hands dirty in the garden, of course) is the antidote to the malaise, the ennui, and the plain old sadness of these times. Many thanks Jerry! Please do take care!
Thank you. I am in Tasmania and find many of your tips very useful. I regularly get aphid infestation on carrots. I use pyrethrum to control them.
This is a very helpful article thanks Jerry. I’m wondering if you have a recommendation of the best book or other resource for easily finding what bug is good or bad? I liked your photos but I’m not in Facebook so checking there if I want to identify something I find would be very difficult.