Three years later Zhang ventured into the popular greenhouse business, growing a shed of tomatoes with his mother on a 5,000 yuan loan.

"The plants grew well until early in the spring of 1991, when the leaves suddenly began to wither and the fruit went rotten," Zhang said. The hopes of mother and son withered, too.

"I had always thought vegetable planting was an easy job," Zhang said.

He learned that the infection that devastated his crops was called "late blight", a factor in the Irish potato famine in the late 1840s, during which millions of people in Ireland starved or were forced to emigrate.

Intrigued by the study of plant diseases, Zhang began to examine the scars on leaves he picked up on the road.

"At first it was I who frequently asked fellow villagers how to prevent and cure diseases, but as time went by, it was they who more and more came to learn why plants grew so well in my greenhouse," Zhang said.

"This made me happy."

He said he had sometimes searched in vain for disease prevention information on the Internet.

"Shouguang is the source of China's greenhouse vegetable planting, so if we couldn't find a solution, it was most likely that no one else could," he said.

In 1998, he filed a patent for a fungicide that could cure late blight disease.

He was now a sought-after agronomist, being invited to travel in Shandong and neighboring provinces to give advice on crop illnesses treatment, and learned how to translate jargon into farmer's clichs.

"Never just tell them how to dilute solutions; tell them how much water they need to add in," he said.

He opened a vegetable clinic in Shouguang in 2002, the first of its kind in China, only to find that local growers were coming in hordes, with more and more trickling in from other provinces through word of mouth.

Inspired by an online video forum, Zhang set up a remote vegetable disease diagnosis system with financing from local government in 2005.

Zhang and his 40-member team provide free service at the Shouguang headquarters. The 300 branch clinics scattered all over the country stream videos on plants affected by diseases.

"We have to train local technicians so they can deal with common diseases themselves," Zhang said. "Only infections or epidemics that they can't handle will be beamed to the headquarters for us to work on."

"You have to try to change some traditional conceptions of farmers," Zhang said. "For example, they think that the more potent a pesticide, the more effective; the more fertilizers, the better."

With this in mind, Zhang created an organic greenhouse vegetable company in 2006, using biological means including insects' natural enemies to prevent pests and diseases.

Zhang's company makes a profit by furnishing growers of the fertilizers and insecticides that it developed. Some of them are made from traditional Chinese medicine.

Zhang said he was using profits from "vegetable hospitals" to offset losses incurred in organic production.

By now he has grown organic vegetables in 60 hectares in Shouguang, with 47 strains certified by the national organic food authorities.

"The organic vegetables are plentiful, but the channels for them to enter the market are few," Zhang said, adding the fundamental snag is the low degree of market reception.

"If one day customers in restaurants say they prefer organic vegetables to the conventional, then our business will really prosper," he said.

Zhang said he had set up a cooperative that accommodates 600 vegetable growers, producing in line with international organic production standards.

By Wang Ximin and Zhao Huanxin (China Daily)

Zhao Ruixue in Shandong contributed to this story.

(China Daily 12/20/2011 page2)