Release of Romanomermis culicivorax for the control of Anopheles albimanus in El Salvador I. Mass production of the nematode.

The mosquito parasite, Romanomermis culicivorax, was mass produced for the treatment of 144,000 m2 of Anopheles albimanus breeding area in El Salvador. The production of the necessary inoculum required the exposure of 1.6 X 10(6) first-instar Culex p. quinque-fasciatus larvae to 137 X 10(6) preparasites (1:14 ratio) each week for 6 weeks. The method employed produced an average 13.7 g (ca. 2,200/g) of postparasitic nematodes per rearing tray (20,000 mosquitoes), a total of 6,392 g (14.1 lb) for the 6-week period, and 425 cultures.

Release of Romanomermis culicivorax for the control of Anopheles albimanus in El Salvador II. Application of the nematode.

The mosquito breeding area of Lake Apastepeque, El Salvador, was treated 11 times over a 7-week period with Romanomermis culicivorax to control Anopheles albimanus and An. p. pseudopunctipennis. Parasitism averaged 58% but varied greatly from treatment to treatment and from site to site. However, three applications made during evening hours to avoid wind and wave action on the lake produced an average 86% parasitism. No significant differences in susceptibility to R. culicivorax were found between instars or between species. Also, no correlation was found between nematode dosage rates and levels of parasitism. Though the parasitism averaged about 60% of the desired level, Anopheles populations dropped from more than 10 per dip at the beginning of the release program to 0.6 per dip at the end of the release period (a 94% reduction). This is the first successful attempt to control mosquitoes on a large scale by using a parasite or pathogen.