WHEAT, bananas and rice can now be immunised against fungal infections in much the same way that people can be vaccinated against disease. Ciba Agriculture has developed an 鈥渁ctivator鈥� spray at its laboratories in Basel, Switzerland, which it says primes plants鈥� defences against attack.
鈥淚t activates the plants鈥� natural defence mechanisms against specific diseases before the infection occurs,鈥� says Andy Watt, marketing manager of the British arm of Ciba Agriculture.
One advantage over conventional fungicides is that it seems to work at much lower doses. According to Watt, 30 grams of the agent per hectare gave the same level of disease control as 750 grams per hectare of conventional fungicide. The tests showed that for the best results in wheat, the agent should be applied in April or May when the main shoot begins to grow. The agent is also effective in bananas and rice.
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The activator is a benzothiadiazole compound, which triggers the plants鈥� 鈥渄efence genes鈥�, encouraging them to produce salicylic acid. Salicylic acid forms part of their natural response to fungal attack, apparently priming their other defences. 鈥淚t鈥檚 particularly active against powdery mildew, which is probably the major fungal disease of wheat in Britain,鈥� says Watt. 鈥淎t worst, it can rob you of 30 per cent of your crop.鈥�
Ciba hopes that its activator, which is called CGA 245, will receive approval in Germany and Switzerland next year and in Britain in 1997.
John Pickett, head of the biological and ecological chemistry department at the Institute for Arable Crops Research in Harpenden, Hertfordshire, believes that the new approach has great potential. He says that it might be possible to modify the approach by genetically engineering defence genes into other plants. These could then be switched on and off by spraying the plants with chemical triggers.
