FIELD EVALUATIONS OF ROMANOMERMIS-YUNANENSIS (NEMATODA, MERMITHIDAE) FOR CONTROL OF CULICINAE MOSQUITOS IN CHINA

The use of Romanomermis yunanensis for the control of Culicinae mosqui toes was field tested in five Chinese provinces from 1986 to 1995. Abo ut 2000-4000/m(2) preparasitic larvae of R. yunanensis were released i n rice paddies, ponds, and streams. This resulted in parasitism rates of 52.2-96.7 % for native Culex tritaeniorhynchus, 35.5-89.5 % for C. quinquefasciatus, 90.1 % for C. shebbearei, 78.3 % for C. pseudovishnu i, and 53.7-92.8 % for C. theileri. In addition, preparasitic larvae o f R. yunanensis were added to small water sites in several towns. This resulted in parasitism rates of 53.0-100 % for Aedes albopictus 90.1 % for As. pseudalbopictus, and 70.9 % for C. tritaeniorhynchus, but on ly 28.3-32.6 % for Ae. albopictus in sites with oily water surface and 6.7-34.2 % for C. theileri in streams with turbid water or with organ ic matter in suspension. These results suggest that under appropriate conditions R. yunanensis should be very effective for controlling Culi cinae mosquitoes both in the country side and within city limits. Prel iminary observations on the establishment of R. yunanensis were made a t natural mosquito breeding sites where preparasitic larvae had been r eleased 1-3 years previously. Some factors determining the effectivene ss of field application are discussed. (C) Orstom/Elsevier, Paris.