Since ancient times, humans have been finding ways to win over pests. The use of chemicals to control pests began with the discovery that sulphur killed bugs in 2500 BC. Perhaps it reached a crescendo in the 1930s with the invention of DDT. It was not until Marine biologist Rachel Carson wrote “A Silent Spring” in 1962 that governments started to think there might be an alternative way to deal with our pest problems. The US government begun funding research into Integrated Pest Management (IPM) in the 1970s.
What is Integrated Pest Management?
IPM involves 3 components that are integrated and compatible (Working together, not against each other) to control pest insects. These are; Biological control, Cultural control and Chemical control.
Biological control
Biological control involves the use of other beneficial/predatory insects as well as birds and lizards to eat pest insects.
For IPM to be successful, monitoring for pests is crucial. Recognising the good bugs is important in deciding if you should spray. Also, monitoring can mean the swift removal of the worst affected plant material to limit the damage and reduce the pest population.
Below is an example of getting onto the problem early. This picture shows black aphid on a cherry tree. In the fore-ground are lady bird beetles, hard at work cleaning the aphids up. The fast removal of the worst affected leaves as well as banding the tree for ants means that the ladybird beetles can get to work. Ants in this case protect the aphids from predatory insects so they can harvest the sap. Sap gets left behind by the sap sucking aphids, which the ants feast on. Banding the tree banishes the ants.
Monitoring for predatory insects can reassure you that spraying is not required. Here is a picture of aphids on a rose. There are healthy aphids in the picture, as well as a large brown/copper coloured aphid which has been parasitised by a parasitic wasp. If a chemical spray was used now, the predators would die too.
Cultural control
Cultural control is about making sure the environment favours the good bugs making it uncomfortable for the bad bugs. For example, the recent fad of no dig gardens has had a surprising consequence. Not tilling the soil has meant the bad bugs have been able to build up. So tilling the soil is useful to reduce the numbers of bad bugs. This brings us to another point – in the vegie patch, it is beneficial to rotate crops.
Irrigating plants so they are not stressed can help the plant stay healthy and ward off disease. Making sure they are not drowning either is helpful.
Managing weeds can reduce the habitat for bad bugs. For example, black aphid can over-winter in dandelions.
Over feeding can lead to lots of sappy new growth- which is delicious to the bad bugs. Gentle feeding with a source of organic fertilizer – like manures is all you need for success.
The time of planting can also play a part. For example, if you plant brassicas (Broccoli, Cabbage, Brussel Sprouts) in the warmer months, then you will have a problem with the white cabbage moth. If planting at these times is crucial for success (as with Brussel sprouts, which should be planted in February), then the use of insect netting is useful. Otherwise, planting in the cooler months is wise, as the white cabbage moth are not present in the winter.
It is very important to create habitat for beneficial insects, birds and lizards. All these animals are Australian native, so it follows that they would rely on Australian native plants for food and a home. Many insects rely on wallaby grasses to overwinter for example. It is beneficial to plant a wide variety of shrubs, ground covers and trees to attract a wide array of beneficial animals. Plants that flower at different times is helpful as insects and birds can eat nectar when there are no bugs to eat.
Two more examples of cultural control;
• Feed citrus no later than September in Melbourne– this will result in the new growth, which should have enough time to harden up before summer when the citrus leaf miner is more likely to hit. They only attack soft, new growth.
• Land Cress can be used as a dead end crop. Cabbage moth will lay its eggs on the Land cress, but the resultant caterpillars are unable to eat the leaves.
Chemical control
Chemical control is only used as a last resort and if the pests are completely overwhelming. This is the main difference between IPM and conventional pesticide-based approach because, as soon as a pesticide is used, you will also be harming any good bugs that are present. Spraying can result in a rebound effect, where the plants are re-infected because the predatory insects are no longer present. Spraying results in repeated spraying.
If necessary, choose a chemical that is specific to the pest. For example, Dipel can be used for caterpillars, without harming other insects. Another example is Gnats a go go, which can be used for indoor plants for gnats.
Remember, that just because a spray is organic does not make it targeted. For example Pyrethrum. This is made from a natural product, but it kills a wide range of insects.
Confidor and Success should be avoided as they have lingering, damaging effects on good bugs.
Practical application in the garden
Switching to IPM takes time. It takes time to build up the predatory insects needed for success. Start by planting some flowering plants, preferably native in the garden. If you have an established garden, you might plant up pots with beneficial plants that you can move around the garden as needed. Australian natives as well as plants with umbelliferous flowers (like parsley, carrots and parsnips) are useful for attracting the good bugs. Allowing these plants to flower is beneficial.
To speed things up, you can buy predatory insects. Bugs For Bugs in Queensland have a very efficient service. You might have to do this for a few seasons, before you establish a population. There are cold tolerant predators, as well as bugs for warmer months. Always make sure you have identified the insects that are a problem in the garden before ordering the good bugs for your garden. You can ask one of the friendly staff at Bulleen Art and Garden to correctly identify the bug if you are unsure.