BEIJING, Jun 22, 2001 -- (dpa) Excessive use of chemical insecticides to control annual plagues of locusts in northern and central China is unlikely to prove a long-term solution and risks damaging the environment, an agricultural expert warned on Friday.
"Locusts are developing immunity to some chemicals," said Zhang Long, head of China Agricultural University's pesticide research center. Nearly all the chemicals used to control locusts cause pollution and 50 percent of them contain organophosphates, Zhang said.
The chemicals enter groundwater, kill useful micro-organisms, degrade the soil and enter the food chain, he said.
Aerial spraying poses the most direct threat to human health, due to the lack of advance warning or inaccurate spraying, he said.
This year's locust plagues have affected 7.7 million hectares of mostly waste land in 10 regions, a similar scale to last year, which was the worst year since 1997, officials said.
"Next year will be almost the same" because of the acquired immunity of some locusts and the absence of predators, Zhang said.
The chemicals kill birds and other natural predators of the locusts but, unlike their foes, the locusts quickly rebuild their numbers, he said.
Zhang and his team have developed pollution-free biological locust control methods, including the use of parasitic insects.
The cheaper biological methods are not used because of the influence of large chemical firms and other economic reasons, Zhang said.
But China's central Asian Xinjiang region is using a total of 600,000 ducks and chickens to control locusts in three areas, the Beijing Evening News said.
Scientists in the Yellow River delta, a major locust breeding ground, have begun a planned 120-million-yuan (14.5 million dollars) project to replace reeds with inedible alfalfa, the China Daily newspaper said earlier.
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