My early days of gardening were accompanied by a fearsome arsenal of hideous, toxic chemicals to tackle pests. I shudder to think of them now that we have become so much more aware of the toll that strong chemicals can take on the complex web of life in our gardens and waterways (as well as potentially on our own health). Sustainable gardening is now the way forward and it is a practice that I try to follow and actively promote. It is actually quite fun to learn new ways to outwit insect foes, and I am always on the lookout for creative ideas.
In my experience, there are various categories of tactics: physical removal of pests, physical exclusion of pests, attracting predators to eat pests, and using 'insect psychology' to control pests. Physical removal is the most basic method, and one I have been familiar with since childhood, when my sisters and I were paid (at a very low rate) to hunt for and destroy snails in the family garden. We became quite adept at finding their hiding places in wood piles, under thick foliage and on the shady side of pots. I now also physically remove the adult forms of the bronze orange beetle (clad in a long-sleeve shirt and wearing goggles to protect myself against the noxious liquid they eject as a defence mechanism when disturbed!). I whack them with a stick from the branches of my citrus trees into a bucket of soapy water. On hot days, these horrible creatures may cluster low down on the trunks of the trees, where it may be easier to remove them. I use a similar technique with the annoying flea beetles that attack my Salvia plants and disfigure their leaves. With these tiny insects, I flick them into a small jar of soapy water and firmly close the lid! Orchid beetles can be tackled in the same way. Physical removal can also be used to pick off and squash caterpillars; rub aphids from stems (they can also be hosed off with a vigorous jet of water); and scrape scale from branches with an old toothbrush.
Physical exclusion covers many varied strategies. My most recent practice has been to enclose each of my developing passionfruit in an organza drawstring bag. Last year, I harvested exactly one passionfruit from what had seemed initially would be a bumper crop. I don't know exactly what ate them - possibly cockatoos, possums and/or bush rats - but it was hugely disappointing. The organza bags (available very cheaply at $2 shops) allow light in and can be tied on securely. Time will tell if the ruse works. Previous attempts at netting the crop failed, as the pests seemed to be able to get beneath the netting and then the vine became hopelessly entangled with it all. The organza bags can, of course, be used with a variety of other crops, such as tomatoes, figs and so on. They are available in a range of sizes.
Because I have many brush turkeys marauding in my neighbourhood, I always place an obelisk or some sort of protective frame over any plant that is put in. They seem magnetically attracted to anything new in the garden and they delight in digging up the plant as the scratch around in the freshly dug soil. Once the plant is established, it seems safe to remove the barrier. Some gardeners lay old, dry palm fronds on the ground in the borders as a deterrent, as it seems the turkeys don't like the feeling of walking on this material.
With my vegetables and herbs grown in pots, I often use a large wooden frame covered in gauze to place over a group of pots to deter flea beetles from my basil and mint, and white cabbage moths from any Brassica crops such as rocket, kale or watercress. This method only works for edibles that don't need insect pollination. Other exclusion ideas include making guards to place over young seedlings by cutting off the top and bottom of a plastic soft drink or milk bottle and placing this over the plant. The top can be covered with soft mesh and held in place with an elastic band for extra protection. Snails can also be deterred from attacking plants by creating a barrier of crushed eggshells or wood ash. Thin adhesive copper tape can also be stuck around the sides of a pot as snails won't cross this material.
Insect psychology is an intriguing form of pest control. The method I am currently trying is the use of faux cabbage moth decoys to keep these wretches from laying eggs on my plants. There seems to be a plague of them at the moment and they are seemingly interested in all plants in my garden, not just the Brassica family! Apparently, these insects are territorial so if they see a moth already on a plant, they won't approach. I have made some decoys from white ribbon and attached them to a wooden skewer, and it seems to be possibly working! I have also ordered some more realistic ones that bob about on a spring which I plan to dot around in my garden. Other techniques to trick insects include the use of a pheromone in an adhesive trap to lure male citrus leaf miners to a sticky demise and thus reduce the overall population of the pest; and placing a saucer of beer at ground level to exploit slugs' and snails' love of a tipple, where they drown quite happily.
Attracting predators to eat insect pests is another handy way to reduce their numbers in your garden. Birds are obviously a great help with this, so making your garden bird friendly - by providing water in a bird bath and growing plants with suitable nectar as well as a dense habit to provide shelter - will mean that birds will be your allies in pest control. Beneficial insects such as hoverflies, lacewings, wasps, ladybirds and predatory mites that eat insect pests can also be encouraged by growing plants that provide food. In general, beneficial insects are small and thus have tiny mouth parts, so nectar and pollen from clusters of tiny, shallow flowers growing horizontally on a flat 'landing platform' are best for these creatures. The Apiaceae family has blooms like this and examples include Queen Anne's lace (Ammi species) and Orlaya, as well as parsley and coriander when they are allowed to flower! The Asteraceae (Compositae) family also has flat flower clusters: what appears to be a single bloom of many of these plants is actually comprised of many tiny 'disc' flowers in the centre, surrounded by larger individual strap-shaped flowers. The disc flowers of many of the members of the daisy family attract beneficial insects. Particular favourites that thrive in our Sydney include yellow chamomile (Anthemis tinctoria), annual sunflowers (Helianthus annuus), annual pot marigolds (Calendula officinalis), Cosmos bipinnatus, Echinacea purpurea and feverfew (Tanacetum parthenium). Avoiding nasty chemical sprays that kill insects indiscriminately is an important aspect of encouraging beneficial insects in your garden.
I do use a couple of organic sprays (which only control the insects that are aimed at) when absolutely necessary: a white-oil based one for aphids, scale, bronze orange beetle when it is in its early stages during winter and early spring, citrus leaf miner and whitefly; and a neem tree extract for caterpillars and grasshoppers. However, I remain fascinated by the idea of outwitting pests and would love to hear your strategies!
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Creative pest control
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