Laboratory evaluation of toxic baits for mosquito (Aedes aegypti) larvae.

Toxic bait discs were prepared by incorporating the larvicide Abate (Temephos) technical, with yeast and dog biscuit (1:1), the latter forming the attractant source. These were assessed in 1, 10 and 25 litre aquaria and 100 litre drums against Aedes aegypti larvae. Floating as well as sinking bait discs were found equally effective in controlling free moving larvae. Larvae confined in artificially suspended cages were not affected. The baits were found effective for 5 to 6 weeks. Toxic disc bait preparation methodology and evaluation protocols are discussed in this communication.

Laboratory and field evaluation of an insecticidal trap for houseflies.

Several substances/food baits and admixtures thereof were tested in a perspex trap, treated with insecticide K-othrine@0.01 mg/cm2. Bioefficacy for housefly trapping was evaluated. Combination of ingredients was found to be more effective than individual ingredients. A combination of some easily available and cheap ingredients were employed for field trials. The admixtures of milk powder, dog biscuit, jaggery and banana peeling was found very effective. The trap efficacy including persistence of the toxicant K-othrine was observed for more than 6 months. Observations on number of flies trapped and utility of such a trap in actual field situation are discussed.

Laboratory evaluation of an ovipositional trap for mosquito adults Aedes aegypti (L.) (Diptera: Culicidae).

A trap was designed, fabricated and evaluated for trapping and killing ovipositing females of the yellow fever mosquito Aedes. aegypti. Water in which larval stages had previously dwelt for 48 hrs. formed the attractant source for ovipositing mosquito females. The trap was evaluated under different experimental conditions. Single choice and double choice experiments were performed with or without glue applied to inner surfaces, to determine trap efficacy. Effect of population size and alteration in assay conditions on percentage catch are discussed.

A device for monitoring and control of mosquitoes by behaviour manipulation.

A trap was designed and fabricated for capturing mosquito larvae based on their behavioural responses to food and light. The larvae upon entering the trap died ultimately due to asphyxiation. Maximum success was achieved with Aedes aegypti larvae in lesser water volumes. The usefulness of the device for studying the response of mosquito larvae and aquatic organisms to chemicals, baits, light, various stimuli and possible pest/vector monitoring and management in aquatic eco-system is discussed.

Comparative repellent properties of certain chemicals against mosquitoes, house flies and cockroaches using modified techniques.

Several terpenoids were assessed for their repellent/toxic properties against mosquitoes (Aedes aegypti), house flies (Musca domestica) and cockroaches (Periplaneta americana). Impregnated wide mesh netting was used in the case of the Dipterans, while treated filtered paper was employed for the bioassays with cockroaches. Persistence of the repellent chemicals was studied. Doses ranged from 5-20 gm/M2 for the Dipterans and 25-100 mg per 4 x 4 cm filter paper for the cockroaches. Dimethyl phthalate (DMP) offered the maximum protection of the chemicals tested against mosquitoes but was not so effective against house flies and cockroaches. Citral and Eugenol were effective against all the three test insects. Other test compounds afforded varying degrees of protection. Application strategy and utility of the findings are discussed.

Vapour toxicity & repellence of some essential oils & terpenoids to adults of Aedes aegypti (L) (Diptera: Culicidae).

Bioefficacy of commercially used synthetic insecticides/repellents and potential of selected essential oils and terpenoids were assessed against mosquitoes. Essential oils and terpenoids, were vapourised in commercially manufactured mosquito repellent electronic assemblies and effects of such vapours were tested on 6-7 days old adult female Aedes aegypti. Commercially available 'mats' (coir rectangles) impregnated with allethrin were used as standards for comparison of Kt50 and Kt90 values. Fastest knock-down was seen in case of allethrin, followed by terpeneol (anhydrous) and (-) carvone. Maximum knock-down time was observed for beta citronellol. All compounds exhibited a repellent effect also, terpeneol (anhydrous) being the best, followed by (-) carvone and citronellal. In repellent tests, no mortality was caused by terpenoids, but allethrin caused > 80 per cent knock-down.

An apparatus for the experimental demonstration of behavioural responses of the cyclopoid copepod, Mesocyclops leuckarti sensu lato to light and temperature.

To demonstrate the behavioural responses of Mesocyclops leuckarti sensu lato to light and temperature, an apparatus was designed and fabricated. It was found that light did not effect the orientational response significantly (p > 0.05) compared to the control. However, temperature gradient definitely influenced the orientational response (p < 0.05). The suitability of this apparatus for studying the behavioural response of other aquatic organisms are also discussed.

Effect of selected chemicals on mosquito larval orientation behaviour using a new apparatus.

An apparatus was designed and fabricated for studying the effects of aromatic chemicals on the IV instar larvae of Aedes aegypti (L.). The test chemicals (essential oils and monoterpenoids) were incorporated in agar along with yeast and dog biscuits which formed an attractant food source (bait). A fairly rapid decrease in the migration of larvae towards the bait cum chemical source was observed during the first hour after which a steady state was observed. Minimum migration (9.67%) was seen with terpeneol anhydrous and maximum (15.0%) with beta-citronellal as compared to control (65.67%), at the end of a 4 hr exposure period. Food particles were also detected on microscopic examination.