A recent army worm infestation in major grain producing regions in North and Northeast China is now under control and will have little effect on this year's harvest, agricultural professionals said.

A farmer checks corn affected by army worms in Beijing's Shunyi district on Tuesday. [Wang Jing/China Daily]

The army worm, a common pest, became the most serious threat to the production of corn this summer in the country's major grain-producing regions due to unusual weather conditions.

By Friday, pest control measures had effectively covered about 3 million hectares, or 80 percent of the total corn planting areas nationwide hit by the infestation, the Ministry of Agriculture said on its website on Monday.

The affected areas include Hebei, Jilin, Liaoning, Heilongjiang provinces, as well as the Inner Mongolia autonomous region and Beijing and Tianjin, the ministry said.

"It has been unusual over the past few decades to see an army worm plague affecting so many places in North and Northeast China. The pest usually appears along the middle and lower reaches of the Yangtze River," said Li Maosong, a researcher of disaster reduction at the Chinese Academy of Agricultural Sciences.

"However, frequent cyclonic activities since mid-July provided favorable conditions to the migration of the army worms, and then heavy rainfall forced them to stay in north and northeastern parts of the country," he said.

At present, the country has successfully stopped the spread of the army worm infestation in the affected areas, and there is no severe impact on corn production, the ministry said.

"Only a small number of farmers in Beijing suffered complete crop failures due to the army worm infestation, although it is the most serious case in the city since 1997," said Yang Jianguo, an official from Beijing Plant Protection Station.

"The total corn output will only see a slight loss because of timely and effective pest control measures," he said.

On Tuesday, the city ended its pest control efforts when the infestation gradually died out due to the short lifetime of the army worms, he said.

Authorities urged local branches to continue to improve surveillance and control efforts to fight against army worms, which are still present in some parts of Northeast China.

By Tuesday, the army worm infestation had affected 1.8 million people and 481,600 hectares of farmland, causing direct economic losses of 1.44 billion yuan ($226 million) in Heilongjiang and Jilin provinces, according to the Ministry of Civil Affairs.

Yao Lucai, who has 1.3 hectares of farmland in Dehui, Jilin, said all his corn leaves have been eaten up by the pests.

"Some have only half cobs left. This is the most serious infestation I've experienced," Yao said.

"I sprayed pesticide for three days, but it's too late. The effect is limited. And the pesticide makes me feel dizzy. My wife even stayed in the hospital for three days because of pesticide poisoning," he said.

"The pesticide price has also soared from 5 yuan per bottle to 14 yuan per bottle. One bottle can be used for 0.07 hectare of land. I have spent over 1,000 yuan on it.

"I think there will be a total crop failure. I'll lose at least 80,000 yuan. For the next year, I'll have to secure a loan to buy seeds and fertilizer."

Li Maosong said China's farmlands will face a serious increase in pests in the future partly because of climate change.

"Some plant diseases that never occurred in the past are very likely to break out. Therefore, more early warning and control efforts should be strengthened," Li said.

In 2011, China's corn output reached 192 million tons. The rise in corn prices last year encouraged Chinese farmers to expand this year's planting area by 2 percent, according to the Ministry of Agriculture.

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Han Junhong in Changchun contributed to this story.