3 May 1996

Aspirin spray takes the headache from control

By Robert Harris

ASPIRIN substitutes which vaccinate plants when sprayed onto leaves will form the basis of many crop disease control programmes by the end of the decade, claim Ciba scientists.

The chemicals work by mimicking the action of salicylic acid, the active ingredient of aspirin, which is produced by plants in response to disease attack.

The acid stimulates production of a binding protein, the equivalent of a human antibody, which protects the rest of the plant from the pathogen, explains Helmut Kessman, the Ciba team leader in Basle, Switzerland.

After several years of screening, Ciba has discovered a chemical, CGA 245704, which triggers the same "systemic activated resistance" when sprayed onto plants.

Initial work on tobacco and cucumber showed the activator was effective against several bacterial, viral and fungal diseases, he says. Further studies show good control of cereal diseases, especially mildew, and downy mildew, a problem in many broad-leaved arable crops.

However, since the activator has no fungicidal properties, it has to be applied before disease is seen, usually slightly earlier than the current GS31-32 timing in cereals, notes Dr Kessman.

But it is active even in adverse conditions, providing protection for two months or more, he claims. UK trial results showed after 50 days only 3% of the leaf area was infected, compared with 11.5% for an azole and 19.5% for the control.

It appears to work in several ways. Initial blocking is by a change in the physical structure of the leaf surface which prevents invasion by fungal hyphae. Any which do succeed are stopped at a later stage.

Unlike fungicides, the activator does not select out less sensitive strains, so there is no chance of resistance. And it is broken down within an hour in the soil, he adds.

Application rates are just 30g/ha, much lower than existing fungicide treatments. It is expected that these could be fine-tuned to different varieties, prolonging the life of resistant ones. &#42

Headache no more… Novel technology could see an aspirin-based spray helping growers wage war on cereal diseases by the end of the decade, say scientists.