No abstract

Dengue and dengue haemorrhagic fever constitute one of the most significant arthropod-borne viral diseases that occur in tropical and subtropical regions in the world. Annually 390 million new dengue cases are being reported from the 128 dengue-endemic countries. Aedes aegypti is the primary vector that transmits the disease. Since the primary vector is a container breeder, source reduction appears to be a good vector control method. Source reduction limits the oviposition of females through oviposition-site deprivation. Therefore, the current study was conducted to determine the effect of oviposition-site deprivation on the fecundity, fertility, life-history parameters, and longevity of Ae. aegypti. Oviposition-site deprivation was enabled by delaying the access to the oviposition substrate. Female mosquitoes were allowed to access the oviposition substrate separately on the day of blood feeding and 2, 4, 6, and 8 days after blood feeding. The results showed that oviposition-site deprivation significantly increased fecundity with an increase in the number of egg retention days. The number of eggs laid by the female increased by 69% when the female was compelled to retain the eggs for 8 days. The highest recorded fecundity was 100 ± 5. Nevertheless, fertility, percentage larval mortality, total larval duration, pupal duration, and longevity were not affected by the number of egg retention days. Thus, it is imperative to have a clear awareness about the effect of oviposition-site deprivation on the reproductive performance of the vector mosquitoes when adopting vector control strategies.

Dengue is a fast-spreading mosquito-borne viral disease in the world. The primary vector of the disease is Aedes aegypti of the family Culicidae. It is a container breeder. Since a vaccine or a drug has not been developed against dengue, vector control appears to be the best method so far to control dengue. The current study was conducted to determine the effect of delayed mating on fecundity, fertility, life-history parameters, and longevity of Ae. aegypti, because such information can help formulate integrated vector control strategies involving the release of sub-fertile males into the environment. During this study, mating was delayed by 0, 2, 5, and 8 days after emergence. Males and females were separated by hand at the pupal stage using the apparent size difference of the sexes. The separated pupae were kept in separate cages until emergence. When mating was delayed for 8 days, the number of eggs laid by the female declined by 38%, and the percentage number of eggs that hatched reduced by 24%. However, the percentage of larval mortality, duration of the larval and pupal periods, and adult longevity were not significantly affected. The current results indicate that delayed mating has a negative effect on the reproductive performance of vector mosquitoes.

Over 90% of the insect damage to cowpea seeds is caused by Callosobruchus maculatus.Although, many chemicals have proven their efficacy against C. maculatus, they adversely affect the natural environment. Death of non-targeted species which are natural enemies of other insect pests and development of resistance to chemicals is possible. Therefore, the current study was conducted to determine the effect of plant leaves of Murraya koenigii ("Karapincha"), Pandanus amaryllifolius ("Rampe"), Vitex negundo ("Nika"), Pavetta indica ("Pavatta") and Croton aromaticus ("Wel keppetiya") on adult mortality, oviposition, and progeny development of C. maculatus. Plant leaves were tested in both fresh form and powdered form. The plant leaves were mixed with cowpea seeds to have two concentrations followed by the introduction of 5 pairs of C. maculatus adults. The maximum adult mortality, minimum oviposition and the minimum progeny development were observed when the cowpea seeds were treated with C. aromaticus leaves. The mortality increased to 100% when the seeds were treated with the combination of C. aromaticus -P. amaryllifolius -V. negundo (WPN) plant leaf powders. This study suggests that fresh plant leaves or plant leaf powder of C. aromaticus can be used against C. maculatus to protect cowpea seeds in storage.