City health officials have detected rising numbers of the pests as temperatures get warmer and rain increases.

Diseases such as dengue fever, encephalitis B and malaria are spread by mosquitoes.

"The most rampant period for mosquitoes is July and August, and flies spread in June," said Leng Pei'en, director of the vector department of Shanghai Disease Prevention and Control Center. "An investigation last month showed a big increase in the two kinds of vermin since April.

"A recent spot check in the city found that 7.88 percent of the 1,269 places with water have mosquito larvae. Drains in residential complexes, man-made ponds and greenbelts are all ideal cradles for the pest," Leng said.

"The most effective method to control mosquitoes is to clean up all places that contain water. Local residents can visit the Website (shawh.gov.cn) to learn about pest-control methods."

Meanwhile, the city has established an emergency plan to deal with infectious diseases spread by pests, and health officials plan to test it with a drill tomorrow in Yangpu District.

Under the plan, health staff should arrive at a patient's home within two hours of being notified of an infection and investigate and exterminate pests by spraying pesticides.

"The area within 100 meters of the patient's residence will be designated an epidemic area, while monitoring and pest control must take place within 500 meters of a patient's home," said Jin Peiwu from the Shanghai Patriotic Health Campaign Committee.