Oviposition response of the mosquito, Culex quinquefasciatus to the secondary metabolite(s) of the fungus, Trichoderma viride

Abstract

Secondary metabolites produced by (Davis & Bowen 1994). By using oviposition attractants, vector mosquitoes could be attracted to chosen sites for laying eggs. Various chemicals serve as oviposition attractants for mosquitoes even when present in relatively small quantities (Beehler & Mulla 1993). Oviposition attractants are known to be produced by microorganisms also (Hazard et al. 1967, Rockett 1987, Hasselschwert & Rockett 1988, Beehler et al. 1994. Among deuteromycetes fungi, Trichoderma species are known to produce aromatic/volatile secondary metabolite(s) (Kikuchi et al. 1974, Keszler et al. 2000, SarhyBagnon et al. 2000, Kalyani et al. 2000. In the present study secondary metabolite(s) produced by the fungus Trichoderma viride was evaluated for oviposition attractancy against gravid females of Culex quinquefasciatus and the results are presented in this paper. MATERIALS AND METHODSA natural strain of T. viride (F24), obtained from the culture collection of Vector Control Research Centre (VCRC) was subcultured on Sabouraud Dextrose Agar (SDA) (glucose 40 g; peptone 10 g; agar 20 g; distilled water 1000 ml; pH 4.5-5.0) slants and incubated for 5 days to attain sporulation. Then a loopful of spores were inoculated to 50 ml Sabouraud Dextrose Broth (SDB) (glucose 40 g; peptone 10 g; agar 20 g; distilled water 1000 ml; pH 4.5-5.0) in a 250 ml conical flask and incubated on a rotary shaker (New Brunswuck Scientific Co., New Jersey, USA) at 110 rpm and at 30°C for 3 days. From the seed culture, 2% of the inoculum was transferred to 200 ml of SDB and incubated for 15 days at the above mentioned conditions. The culture was filtered through Whatman no.1 filter paper, the mycelial mass was discarded, and the culture filtrate was lyophilized. The residue was dissolved in 50% ethanol at a ratio of 500 mg of residue in 10 ml of ethanol. This formulation was code named as VCRC F24 and used for oviposition attractancy tests.Determination of optimum concentration of VCRC F24 and p-cresol for oviposition attractancy test -Threeday-old Cx. quinquefasciatus Say female mosquitoes, an indigenous strain obtained from a laboratory colony maintained at VCRC, were fed on fowl blood and maintained for two days on raisins at 28 ± 2 o C and 70-80% RH. Gravid female mosquitoes were used for the determination of oviposition attractancy using standard procedure (WHO 1963). Different concentrations (5 µg ml -1 , 10 µg ml -1 and 15 µg ml -1 ) of VCRC F24 and a known oviposition attractant, p-cresol (a volatile pentane), was prepared in tap water. In the case of p-cresol, a stock solution of 1mg ml -1 was made in ethanol and diluted to the required levels with tap water. Tap water with equal amount of ethanol served as control for VCRC F24 and p-cresol. Two hundred ml of each of the test/control solutions held in disposable bowls (capacity, 250 ml) were placed in the floor of a mosquito cage (size, 55 x 55 x 55 cm). One hundred numbers of fully gravid female mosquitoes were released into the cage. For each test at any given time, not more...

Larvicidal and ovicidal properties of leaf and seed extracts of Delonix elata (L.) Gamble (Family: Fabaceae) against malaria (Anopheles stephensi Liston) and dengue (Aedes aegypti Linn.) (Diptera: Culicidae) vector mosquitoes

“…Botanical phytochemicals with mosquitocidal potential are now recognized as potent alternative insecticides to replace synthetic insecticides in mosquito control programs due to their excellent larvicidal, pupicidal, and adulticidal properties. Many synthetic insecticides and naturally occurring chemical cues have been shown to influence mosquito oviposition (Geetha et al 2003). A few insecticides in common use have also exhibited high-deterrent activity, causing negative ovipositional response (Moore 1977).…”

Oviposition-deterrent, ovicidal, and repellent activities of indigenous plant extracts against Anopheles subpictus Grassi (Diptera: Culicidae)

“…Many synthetic insecticides and naturally occurring chemical cues have been shown to influence mosquito oviposition (Millar et al, 1992;Olagbemiro et al, 1999;Geetha et al, 2003). A few insecticides in common use have also exhibited high-deterrent activity, causing negative ovipositional response (Moore, 1977).…”

Laboratory and field evaluation of an oviposition trap for Culex quinquefasciatus(Diptera: Culicidae)

“…Fermented infusions of plant material or animal excreta (Bentley & Day 1989, Reisen & Meyer 1990, Lee & Kokas 2004 as well as compounds extracted from grass infusion show strong attractiveness to gravid Culex females (Blackwell et al 1993, Millar et al 1994, Mboera et al 2000. Volatile chemicals produced by some species of fungus and bacteria (Poonam et al 2002, Geetha et al 2003 have been shown to be highly active as oviposition attractants for Cx. quinquefasciatus.…”