Green thumb
The early bird catches the worm and monitoring is the first course of action for pest control
Organic farming using natural pest control was the way all crops were grown before World War II when, as part of the war effort, synthesised pesticides were developed. Lately, people have become concerned about chemical residues on food, while empty shelves in supermarkets have heightened concerns about food security.
More and more people are wanting to grow their own food organically.
In the new paradigm of climate change, we are witnessing today, extreme weather events across the planet are all contributing to global food insecurity.
In this hotter world, insects that once had one or two generations in a summer season are now “loving” the advantage of the heat and are breeding four or five times a season.
Growing food becomes even more difficult when we face the incursion of exotic horticultural pests into Australia as we have seen over the last few years. It threatens our biosecurity, and our farmers face the prospect of battling new pests that change the natural balance of native insects.
How can we overcome these challenges? Does nature have the answer?
We know healthy plants produce their own repellents and that is particularly evident in plants grown organically. Healthy soil contains millions of microbes and these microbes perform the most important ecosystem services for the gardener/farmer.
In a natural system, soil microbes control pathogens and repel insect pests. They manipulate the soil’s structure and provide the medium to grow healthy foods.
For thousands of years, farmers have understood and used organic controls to manage pests.
The early bird catches the worm and monitoring is the first course of action for pest control. Early mornings and very late afternoons are the times to detect pests, especially the caterpillars of moths and the larval stages of some beetles that are active from dusk to dawn. It is surprising how much control can be achieved by examining plants at these times and either removing the moth’s eggs and caterpillars by hand or using a botanical formulation to stun the moth before it lays eggs.
Sticky yellow cards and traps containing a pherodis dispenser can be used to trap and help monitor pests, but be aware sticky traps will catch all insects including the beneficial ones.
Exclusion nets can be built over the garden bed to control pests, but be mindful that they will also exclude pollinators that are necessary in flowering crops such as eggplant, tomatoes, cucumbers and zucchini.
Repelling pest insects is the easiest action to take and can be achieved by interplanting vulnerable crops such as cabbage and broccoli with onions, and planting a hedge of repellent citronella grass or Thai basil as a line of defence.
Citronella grass will grow 1.5m high and has stalks with flower spikes 1m higher so it needs room to grow, however, the grass can be cut back and it will regrow quickly and the strappy, long, leaves make the perfect mulch to repel cut worms and deter beetles from laying eggs.
Citronella grass is also an excellent mosquito repellent plant and can be used as a protective barrier around outdoor entertainment areas.
Thai basil is a perennial basil, delicious in pesto and tomato sauces and is also a very good insect repellent. It repels mosquitoes, flies and fleas. Thai basil will grow to 1m in height and its growth responds well to organic fertiliser. Thai basil will grow in full sun or part shade and best of all, this basil is resistant to rust and leaf rots.
To make a repellent spray, harvest a 2L bowl of Thai basil leaves, cover with hot (but not boiling) water and leave to steep overnight. Strain and add a teaspoon of liquid detergent and one of bicarb of soda to 1L of the basil tea, and use to spray for caterpillars and aphids.
Extracts from the neem tree, which is native to India, will prevent insects’ predation on horticultural crops, but unfortunately it has become a pest in some parts of Australia. It seems that here in the Far North, the tree does not readily set seed and if it does, the seed has a low viability and few dispersal agents, but be responsible and remove and dispose of seed when observed.
In the garden, Neem oil has proven effective as a pesticide and fungicide. It works on pests by smothering insects, mites and caterpillars.
Neem leaf extract – Azadirachtin products – are extracted from neem seed and leaves. The resulting product works as a feeding deterrent and growth regulator which disrupts the pest insect’s life cycle. Azadirachtin is also systemic and will control leaf miners and leaf-curl caterpillar. Neem products degrade quickly in the environment, but they do not discriminate between good and bad bugs.
A natural balance of beneficial insects will maintain control. Predatory mites, wasps, lady bugs, praying mantis, spiders and birds, particularly willy wagtails play an important role in reducing pest insects in the garden.
Bees and butterflies are needed in the garden for pollination, so take care when using any insect control method and aim to obtain a natural balance and accept a few chewed leaves on harvest for the reward of a nutritious and delicious, chemical-free vegetable.