(This is an article that I wrote for the August 2010 Food and Wine supplement of the Mercury)
I was asked a question recently about the safety of so called organic pesticides and fungicides. It is an interesting observation that most of us cannot see beyond the industrial farming paradigm. There is the assumption that any vegetable planted must be sprayed and drenched with wonder products otherwise it will be devastated overnight. So, obviously organic farmers must do the same, but with approved organic substances. The truth is that we do things a lot differently.
The emphasis of Organic pest and disease control is prevention. To do this organic farmers employ a number of methods.
The first is our focus on the soil. The soil is the foundation of Organic farming. A healthy soil means healthy plants, healthy animals and healthy humans. A healthy soil is rich in biodiversity. Each species of soil organism plays its part in enhancing the health of the crops that grow in it.
For instance mycorrhiza fungi interact with plant roots to improve their ability to take up nutrients.
A healthy plant has a healthy immune system and is able to produce sufficient of its own phytochemical defences against pests and diseases. Pests, like all predators will always seek out the weak first. Pests like nothing better than a field full of nitrogen bloated, chemically fed crops.
Our second method is to protect and enhance the biodiversity and balance of the natural environment of the farm. We rely on beneficial fungi, bacteria, plants, and animals to control pests through predation and repelling them. Birds and bats are some of our best pest control agents.
Thirdly we employ inter-cropping to help minimize the chances of disease or infestation. Inter-cropping means planting many different crops together rather than as a mono-crop or the same crop in a large area. This reduces the footprint of each crop and allows the different crop species to work together in mutually beneficial ways. Some plants such as the aromatic herbs repel insects, while other crops act as trap crops luring the pests away from others.
The fourth method is rotation. Rotation means planting different crops in succession and never in the same place twice in a row. Each crops adds substances and removes nutrients differently from the soil. For instance Rocket adds substances that repel root nematodes. Rotation enhances soil quality and biodiversity.
Fifthly, organic farmers try and plant seasonally. Crops planted in season will always be healthier and more hardy than those planted out of season. Swiss chard planted over our hot season is susceptible to cercospora spot. Swiss Chard purchased during this period has more than likely been heavily sprayed with fungicide.
If all else fails organic farmers can use certain natural approved substances to cure an infestation but only after seeking permission from the certifying body. However if an infestation occurs the impact is minimised by the diversity of an organic farm and most attacks are short lived.
The use of organic pesticides must be seen as a last resort and most organic farmers do not use them.