Over 400 square kilometers of agricultural land in the capital has been decimated by a plague of oriental army worms, Beijing Plant Protection Unit said Monday.

It is likely that the high numbers of the pest, which targets crop land en masse, and then moves on to the next field like an army battalion, have been exacerbated by the recent heavy rainfall the capital has seen, said an agricultural expert.

But some local authorities Monday downplayed the extent of the damage, claiming the destruction wrought by the worms, which despite the name are actually moth caterpillars, has been exaggerated.

Meanwhile, the neighboring  provinces of Hebei and Liaoning and the Inner Mongolia Autonomous Region have all witnessed the same invasion of army worms, the Beijing News reported.

Sun Pinglan, who lives in Xilihe village in Daxing district, has seen the full extent of the damage the army worm can do to crops. 

Although the caterpillars were spotted in previous years, this is by far the worst infestation she has seen, said Sun.

"Around half of my 9,333 square meters of corn crop has been damaged by the army worms," she said.

Sun said that although two villagers have been sent to hospital suffering from pesticide poisoning, in an attempt to combat the caterpillars, she still will have to take the risk herself to try to save her crop before more plants are destroyed. 

"I might be looking at a loss of 6,000 yuan [$943.2], which is more than half of our total annual revenue," she said, "this is not enough to even cover the seed costs."

Wang Zhenying, director of the Agricultural Insect Research Office of the Plant Protection Department of the China Academy of Agricultural Sciences, said that oriental army worms are distributed throughout Asia.

Historically, the caterpillars have long been recognized as a plant pest in China, he said.

"They are migrants that settle in southwestern China during winter and fly to northern China for summer as a moth," he said.

"The huge numbers [of them] this year is partially to do with the recent stormy weather, which nourished the grasses on which the moths lay their eggs," he said.

A media officer, surnamed Yu, from Daxing district government told the Global Times that everything is now under control.

"This army worm damage is just like that from the unexpected rainstorm," he said.

"But the Beijing government has worked on this and now the situation is no longer severe," said Yu.

A female employee from Beijing Plant Protection Unit, who declined to be named, confirmed that the government has taken action to try to halt the crop damage, which has so far affected 67 villages and townships in the capital region. 

"We discovered the oriental army worms were spreading early last week, and we quickly reported it to the Ministry of Agriculture," she said.

"Meanwhile, we have dispatched the necessary items like pesticide to some areas to kill them," she said.

Yet she also alleged that since the worms have reached maturity,  it is now impossible to stop them. 

"It means they are more pesticide resistant and will cause more damage to corn crops," she noted.

But Sun said that so far, she has not received any official support. 

"We were just informed by the officials via loudspeaker several days ago that we need to pay more attention to these army worms and use pesticide to tackle them," she said.

Apart from Daxing, Tongzhou and Pinggu districts are also affected by oriental army worms, said Wang.

Yet an anonymous media officer from Pinggu government alleged that he had not heard of them. 

"Why do you still care about this when everyone is paying attention to the flood and rains?" he asked the reporter.

Wang said the government should take effective precautions at least two weeks before the caterpillars become mature and so more destructive.

"It normally takes about nine days for the baby caterpillar to become mature," he said.

"Given the intensive planting of corn in the rural areas of Beijing, the work on controlling the pests is going to be difficult now," Wang noted.