Dr. Tom Mew, head of the Entomology and Plant Pathology Division, International Rice Research Institute (IRRI) calls himself a dreamer. It's not the common perception of a man who has followed a career of high science, but he's adamant: "If you're not a dreamer, then, as a scientist, you won't be an achiever!"

Dr. Mew's dreams and his science have provided one of the biggest rice research success stories of 1999.

With a simple management strategy, IRRI scientists coordinated by Dr. Mew, in collaboration with scientists from Yunnan Agricultural University, have controlled a devastating fungal epidemic threatening to wreak havoc in the huge Chinese rice crop.

The disease, blast, causes heavy yield losses in temperate and subtropical rice crops. It is one of the most serious diseases affecting rice production in China.

"They were using huge quantities of fungicide," Dr. Mew says, "sometimes spraying a single crop six or seven times. We didn't know what kind of environmental damage that was causing."

Three years ago, IRRI developed a new project in consultation with the national agricultural research systems (NARS) of China, Thailand, Vietnam, and the Philippines. It was called "Exploiting Biodiversity for Sustainable Pest Management," and its work began at a time when modern agriculture was being criticized as the cause of frequent epidemics and pest problems because of genetic uniformity, high fertilizer and chemical inputs, and high production through the monoculture of single cultivars across large areas. The blast problem in China involved all these factors. It quickly became the project's first priority.

Recipe for an Epidemic

The scientists reasoned that, in a massive, single-variety rice crop, such as that grown in the Red River Valley of Yunnan, in southwestern China, a single disease such as blast could easily explode into an epidemic. After the pathogen adapted itself to the physiology of one plant, it was then ready and able to attack the remainder of the crop. If there was biodiversity in the crop, however, and if the pathogen was surrounded by dissimilar plants, it was unlikely to achieve a population explosion.

"Our challenge was to simulate a situation in which natural resistance to pests or diseases was diversified through a varietal deployment strategy in actual rice farming," Dr. Mew says. "We focused on interplanting, or growing different varieties of rice in the same field. At the beginning, there was doubt and skepticism."

But an experiment in 1997 covering a few hectares suggested that interplanting could achieve 92 to 99 percent control of rice blast as well as attain an unexpected double success by boosting farmers' yields, which increased by half a ton to 1 ton per hectare.

In 1998, 812 hectares were planted with hybrid rice and glutinous rice, four rows of one and one row of the other. The crop was sprayed with fungicide only once. Yields reached 9 tons of hybrid rice and nearly 1 ton of glutinous rice per hectare. Even more impressive was the fact that within the interplanted crop the incidence of blast fell to five percent from a common level of 55 percent, and the yield loss dropped from 28 percent to nothing at all.

Last year, the area grew to 3,342 hectares, and the farmers involved boasted that interplanting was providing them with about US$150 more income per hectare.

Chinese national television got into the act, producing a full-scale documentary on the interplanting experiment. The authorities in Yunnan Province organized a field day for other provincial agricultural researchers. Then they set up training schemes to pass the technology on to others. The Chinese Ministry of Science and Technology also became very interested.

The Idea Catches On

By the end of 2000, the IRRI-Yunnan research team plans to extend the scheme to cover up to 60,000 hectares.

"Eventually, we'll see the whole Yunnan Province involved," Dr. Mew says confidently. "That's close to one million hectares of rice farming.

"The key is to use different varieties, with different resistance genes. Never plant the same varieties every season. Rotate them. Never again allow the pathogen to dominate. Achieve an equilibrium."

Dr. Mew says that the success of the interplanting procedure has gone even farther than defeating the blast problem and increasing farmers' incomes. Fungicide has been substantially reduced, and he expects that the effectiveness of natural genetic resistance to blast will now last longer. Previously, genetic resistance, carefully bred into new varieties, lasted only about three years because the blast pathogen quickly adapted itself to the new plants.

Hitting the Jackpot

Dr. Mew says that rice blast is also a very big problem in northeast Thailand.

"Maybe the same approach will work there," he says. "If it does, then we've really hit the jackpot. But this doesn't start and end with blast. Our interest now is to see what effect varietal or germplasm diversification of rice cropping has against other pests. "We may not be able to affect endemic pests, but we may, at least, be able to prevent large outbreaks."

Dr. Mew is quick to give credit to researchers from NARS who collaborated in the biodiversity project, and particularly to Professors Chen Hairun and Zhu Youyoung of Yunnan Agricultural University.

"It is successful because our partners were committed to it," he says. "They understood it and made it succeed."

This is Dr. Tom Mew's 25th year at IRRI.

"When I first joined IRRI, I ate a lot of rice, but I knew nothing about the plant, or growing it, and I'm still learning," he says. "But there's no doubt that these years have been the most productive of my professional career."

The Malaysian scientist is 60 years old and is "looking forward to a few more years' work before retirement."

He is concerned that IRRI must continue to provide world leadership in rice research.

"Science is developing very fast, and it will be difficult for IRRI to maintain its leading position if we don't work hard and smart. Rice diseases and pests are shifty enemies. If we're not one step ahead of the problems of world rice production, then we're never going to be able to solve them."

He has a few words of advice for his younger IRRI colleagues: "Younger scientists must get out into the field to understand rice; rice doesn't grow in offices and laboratories. They must quickly establish a good understanding of the crop where it is grown-in farmers' fields. They must keep one foot in the field and the other in the halls of science." IRRI, with its headquarters in the Philippines and offices in 11 other countries, is the world's leading international rice research and training center. It is an autonomous, nonprofit institution that is focused on improving the well-being of present and future generations of rice farmers and consumers, particularly those with low incomes, while preserving natural resources. IRRI is part of the Consultative Group on International Agricultural Research (CGIAR), an association of public and private donor agencies that funds 16 international research centers.

For more information visit the CGIAR www.cgiar.org or Future Harvest websites www.futureharvest.org. Future Harvest is an initiative of the 16 CGIAR research centers and their donor agencies to raise public awareness of the importance of agricultural research.

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