Larvicidal activity of some plant extracts to larvae of the mosquito Culex quinquefasciatus (Say 1823).

OBJECTIVES AND METHODS: Searching for potent plant larvicides, crude aqueous extract of the latex of Uschar (Calotropis procera) and Labakh (Ficus benghalensis) were tested against the fourth instar larvae of the lymphatic filariasis vector Culex quinquefasciatus (Diptera: Culicidae) using the conventional methods recommended by the WHO. Likewise, the toxicity level of Malathion was tested. The dose/response mortality relationship was statistically determined using double transformation regression analysis. The 24-hour LC50 of the test agents was taken as a measure of its acute toxicity. The 24-hour LC50 of Malathion to the larvae was 2.2693 mg/L. The most potent plant extract was the latex of Uschar which killed 50% of the larval population at a concentration of 0.0062% (V/V). RESULTS: The 24-hour LC50 of Labakh latex was 0.4796% (V/V). A range of concentration extending between 0.0195 and 10% (W/V) of the Labakh fruits (figs) produced more or less the same % of mortality (25%). CONCLUSION: Since the latex of the plants tested are hazardous to man and his animals, it is recommended that these extract must be used in bodies of water not accessible to man or animals such as pit latrines and septic tanks.

Studies on phlebotomine sandflies in an active focus of leishmaniasis in the Sudan.

The present work is a pilot experiment meant to provide base line information on cutaneous and visceral leishmaniasis in an active focus on the White Nile, Sudan. The topics covered include species of sandflies prevailing in the area, anthropophily, endophily, suspected vector and reservoir host, seasonal and daily rhythm of activity and susceptibility to insecticides.

The food of the larvivorous fish Gambusia affinis (Baird and Girard) and Oreochromis (formerly Tilapia) niloticus (Linnaeus) in Gezira irrigation canals.

The food of both Gambusia affinis and Oreochromis niloticus was studied. Organisms eaten by both species of fish are tabulated, together with the amounts eaten during the various months of the year. G. affinis larger than 25 mm are carnivorous and become more so with age. Food selection by G. affinis depends on the availability of food items rather than choice. It showed a marked preference for mosquito larvae. O. niloticus smaller than 150 mm were markedly carnivorous, but this decreased with age. Only small fish of this species are useful for the biological control of mosquitoes. Fish larger than 150 mm showed a marked preference for higher aquatic macrophytes.

The impact of the exotic fish Gambusia affinis (Baird and Girard) on some natural predators of immature mosquitoes.

The effects of Gambusia affinis on some suspected predators of mosquitoes were studied for a period of 12 months. A list of such predators was given. The most abundant invertebrate predators were Odonata, followed by Hemiptera and Ephemeroptera and the least common were Coleoptera. The population density of mosquito predators, with exception of Notonectidae and the fish Oreochromis niloticus, was markedly reduced in the presence of G. affinis. Application of aerial pesticides reduced the population of both G. affinis and O. niloticus fish. However it had no effect on the numbers of all invertebrate predators.