Sophie Thomson’s witty, warm and wise approach brought some organic balance to the subject when she spoke to home gardeners at the Botanic Gardens of Adelaide this week.
The basic principle we need to understand, she explained, is whether a plant is happy or not. We need to meet the plant’s required growing conditions, both above and below ground, in order for it to thrive and be able to withstand most of the common bugs that would otherwise attack it. Good soil is the most important condition, and we needn’t despair if our gardening journey starts out inauspiciously because it takes a good three years of building up the soil with regular additions of organic matter before the plants can really bliss out.
Compost turns the soil into a sponge, which can hold and release moisture as needed and in turn reduce the stress on plants. A vital part of the compost’s role in soil is to feed microbes and worms, which contribute to the plants being better defended against nematodes and pathogens. Sophie described the role of beneficial soil microbes in a way akin to the probiotics that we use to create a healthy internal ecosystem in our own guts…if you create good living conditions for helpful microbes in the soil, then they vastly outnumber the microbes that lead to disease, so plants thrive. Organic matter, primarily compost, is the number one ingredient to achieve this. “Put a $1 plant in a $10 hole,” Sophie advised… we need to keep adding that organic matter.
If a plant is suffering from a bug attack, we need to correctly identify the bug, and more importantly identify why the plant is vulnerable to attack. Once you have done all you can to support the plant, consider whether the bug warrants any action… exclusion, deterrence, or attack?
Here are Sophie’s tips on managing some of the common garden pests…
Aphids… spray them? Smoosh them? Hose them off? None of the above! Just give their predators a chance to get onto them. What predators? Ladybirds, parasitic wasps…let some herbs and vegetables go to seed in the garden to attract these helpers and they’ll do the work for you, chemical-free. So where are they? Hiding amongst those damn aphids!! If you smoosh the problem, you’re probably also squishing the solution in the form of ladybird eggs or larvae on the leaves and wasp larvae inside the already mummified aphids that are frozen on the leaves. The aphids will be back in no time, but it will take longer for the predators to breed up again and vanquish them. Don’t believe that another insect can handle so many aphids? One wasp can kill 300 aphids. Not bad eh?
Attract lacewings, hoverflies, parasitic wasps and insect-eating birds by providing a diverse garden containing flowers all year round with nectar to sustain the predators. The only time to spray aphids is when there are no predators around (e.g. on winter vegetables), and then keep your spraying natural, organic and localised so you don’t inadvertently kill off your best garden helpers. If you really can’t help yourself, just hose them off.
Mosquitoes – this was my favourite bit, complete with a real microbat just to prove that they really exist (most of us just mistake them for moths) – these little guys can knock off 1700 mozzies in a night! They live in the hollows formed when tree branches break off (not cut off neatly) – so habitat is key – but the good news is that you can make bat boxes to give them a home – as Josh Byrne’s fact sheet shows.
Caterpillars – white cabbage moths and their dastardly green caterpillars drive us nuts when they attack thriving vegetable seedlings. Surely a case for spraying? Not so fast, says Sophie – you could lock them out with an exclusion net (just mind you’re not locking them IN if they got there first!) or appeal to their territorial instincts by placing fake white butterflies all around your vegies to tell them that this patch is already ‘taken’… yogurt containers are the perfect material for cutting out little butterflies that can be pinned onto stakes or hung from strings over those leafy greens.
Snails and slugs – aim to really dent their population for months, with three successive nights of torchlit hunting and stomping. If that’s not your style, you could sacrifice a little beer or vegemite and water in a snail trap, or use iron-based snail baits in the same way. Blue-tongue lizards eat snails, but then they also love lettuce and strawberries (I’d be putting those in a raised bed out of their way).
Earwigs – a great tip from Annemarie Brookman of the Food Forest via Sophie: grow a sacrificial row of Cos lettuces alongside all your other favourite lettuces – the earwigs like Cos best and that’s where they’ll snuggle in. And chooks love a bit of earwig with their Cos lettuce in the morning! Another earwig recipe for happy chooks – use dreggy sardine tins, topped up with a bit of extra cheap oil, or any old vegetable oil with a dash of soy sauce, to attract and trap earwigs and marinate them for a real chook treat.
Whitefly – usually a sign that plants are over-watered, so cut back on the water and/or use yellow sticky traps to catch them – with a plastic guard to prevent small birds from getting stuck. Also attack the whitefly’s winter hiding places (evergreens) with eco oil in winter, so they don’t get a chance to wreck your tomatoes and mint in spring.
Slaters – often get blamed for being at the scene of the crime when they are actually just cleaning up the damage done by others, but if they or their mates are chomping into delicate seedlings, try putting plastic cups or containers with the bottoms cut out into the soil around the plants until they have grown big enough to cope.
Above all, this talk reminded me that when we take care of the good stuff in the garden (the soil and the beneficial microbes, worms, insects, birds and lizards), then most of the annoying stuff takes care of itself – and for the rest, there is generally a non-toxic solution at hand if we understand the nature of the problem.