Crop rotation cannot get rid of pests and plant diseases any more than regular exercise and eating right can prevent illnesses altogether ("Crop rotation still best way to ward off pests" by Mr Tai Seng Yee; letter below).
The only sustainable, effective and sensible way to deal with pests is an integrated pest management regime combining good cultural practices and some well-researched synthetic chemical applications.
Mr Tai said the bacterium, Bacillus thuringiensis (BT), is the most common organic pesticide used in South-east Asia.
BT merely addresses a very specific issue. But what about the other pests and diseases an organic crop farmer will face from time to time?
Mr Tai also stated that "synthetic pesticides are certainly not safer" than organic ones.
Unlike for organic pesticides, synthetic pesticides' toxicity has been researched extensively, and the extent of their toxicology is well-documented.
Meaningful crop and food production through organic farming methods is a myth.
Organic farming cannot produce enough food to feed a large number of people. On top of that, producing organic food even on a small and manageable scale cannot be achieved consistently.
This is particularly true in the humid tropics, where climatic conditions are conducive to pest and disease outbreaks. No products approved for organic farming can cope with these frequent and intense outbreaks.
Hence, any success in producing an organic food crop will mean high costs - and very high selling prices.
If a buyer finds any organic food product priced not much higher than conventional products, he should be wary of its authenticity.
Letter from Liew Ching Seng
Crop rotation still best way to ward off pests
As the manager of an organic agricultural company, I am aware that the most common organic pesticide used in South-east Asia is BT or Bacillus thuringiensis ("Is organic food really free from pesticides?"; Aug 9).
This is a bacterium that produces crystal proteins that, when ingested by insect larvae, release a toxin which causes starvation. Because of the specificity of its action, BT has little or no effect on humans, wildlife and beneficial insects.
Some 70 per cent of the labour work in organic farms is weeding; herbicides are conveniently used in industrial farms to do the job.
According to the pesticides report of the United States Environmental Protection Agency, 514 million kg of pesticides were used in the US in 2007, of which 241 million kg were herbicides - more than five times the insecticides used.
As a responsible manager, I read the organic standards clearly before allowing any compound to be used in the organic farm.
While many studies on the long-term effects of organic pesticides are still needed, our current understanding is that synthetic pesticides are certainly not safer.
Crop rotation, a common practice at organic farms, is the best way to confuse the insects' dining patterns and protect juicy organic vegetables from them - and the best bet to provide a safer environment and food source for us.
Letter from Tai Seng Yee
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