Indoxacarb gel bait was evaluated for its efficacy in the laboratory and field against American cockroaches, Periplaneta americana (L.), and German cockroaches, Blattella germanica (L.). Advion 0.6% indoxacarb gel bait was toxic to both P. americana and B. germanica. There were no significant differences in the LT50 (h) values for treatment levels of 0.25 g, 0.5 g, and 1.0 g gel applied against P. americana, whereas gel applied at 0.5 g to B. germanica had a significantly greater LT50 (h) in the laboratory than the gel treatments on P. americana. The LT50 for both cockroach species ranged from 40.65 to 145.60 h. There was no control mortality in the laboratory bioassays. In the field, 55 houses were treated with 0.5 g of 6-8 spots of indoxacarb gel bait per kitchen of two or three bedroom bungalows from three Local Government Areas of Lagos State, comprising Surulere (22), Alimosho (12), and Shomolu (21). Mean reduction in cockroach populations varied from location to location based on the level of infestations. Percentage reductions in the indoxacarb gel-treated units ranged from 3.5% at 1 d after treatment to 99.8% at 14 d at Surulere, while reductions ranged from 8.9% at 1 d after treatment to 99.7% at 14 d at Shomolu; a similar trend was observed for Alimosho. Indoxacarb gel bait was highly effective in the control of cockroaches.

The development of insecticide resistance in different species of mosquitoes to Pyrethroids is a major challenge for vector-borne diseases transmitted by mosquitoes. Failure of Pyrethroids in control of mosquitoes would impact negatively on the gains recorded in control of mosquito-borne diseases in previous years. In anticipation of a country-wide deployment of Pyrethroid-treated nets for control of mosquito-borne diseases in Nigeria, this study assessed susceptibility of Culex quinquefasciatus Say. (Diptera: Culicidae) to Pyrethroids in Owhelogbo, Ejeme and Oria-Abraka communities in Delta State, Niger-Delta, Nigeria. Three to five day old Cx. quinquefasciatus were exposed to Deltamethrin (0.05%), Permethrin (0.75%), and Alphacypermethrin (0.05%) using World Health Organization bioassay method. Polymerase chain reaction (PCR) was employed in characterization of species and knockdown mutation. Results revealed that Cx. quinquefasciatus were generally susceptible (98-100%) to Deltamethrin, Permethrin, and Alphacypermethrin in the three communities with the exception of Owhelogbo where resistance to Deltamethrin (97%) was suspected. Knockdown time to Deltamethrin (11.51, 11.23, and 12.68 min), Permethrin (28.75, 13.26, and 14.49 min), and Alphacypermethrin (15.07, 12.50, and 13.03 min) were considerably low for Owhelogbo, Ejeme, and Oria-Abraka Cx. quinquefasciatus populations, respectively. Species identification result showed that all amplified samples were Cx. quinquefasciatus; however, no kdr allele was found in the three populations. Deployment of pyrethroid-treated nets for control of mosquito-borne diseases in Niger-Delta region of Nigeria is capable of reducing burden of diseases transmitted by Cx. quinquefasciatus as well as addressing nuisance value of the vector; however, caution must be entertained so as not to increase selection pressure thereby aiding resistance development.

No abstract

The use of larval source management (LSM) in sub-Saharan Africa is limited, however, widespread report of insecticide resistance in adult mosquitoes has engendered renewed interest in LSM; especially larviciding. Hence, this study evaluated bioefficacy and residual efficacy of commercially available larvicides; Temephos, Spinosad, Bacillus thuringiensis var. isrealensis (Bti) and Bacillus thuringiensis var. israelensis/Bacillus sphaericus (Bti/Bs) on larvae of Anopheles gambiae s.l, Culex quinquefasciatus and Aedes aegypti in Lagos, Nigeria. Acute toxicity assay was used to determine LC95 and the LC95 was doubled to determine discriminating doses. Residual efficacy was assessed by exposing larvae to discriminating doses of larvicides in deionised water and in water collected from larval habitat for 28 days and 24 hr mortality post-introduction of larvae was checked for 2nd, 4th, 7th, 14th, 21st and 28th day. Probit analysis was used to estimate LC95 and residual efficacy at mortality ≥95%. T-Test was used to determine the level of significance (P<0.05) of the residual effect. Temephos (0.007mg/l) was the most toxic considering 24h LC95. The trend of LC95 (Temephos < Spinosad < Bti/Bs < Bti) in Anopheles gambiae s.l was the same for Culex quinquefasciatus and Aedes aegypti. Residual effect of Bti/Bs > Bti > Temephos > Spinosad on mosquito larvae from Lagos, Nigeria. The trend of residual efficacy is the same in both bioassays albeit reduced when larvicides were dissolved in water collected from larval habitats. Strong bioefficacy and better residual capacity of Bti/Bs make it a better larviciding agent against Anopheles gambiae s.l, Culex quinquefasciatus and Aedes aegypti in Lagos, Nigeria.

The toxicological and residual properties of two insecticidal agents, Deltamethrin and Chlorpyrifos were evaluated against the German cockroach, Blatella germanica in laboratory bioassay. The insecticides were diluted in both aqueous and oil-based solvents and tested against the roaches in pre-determined concentrations and untreated control. Experimental cages were either completely sealed after exposure or perforated to simulate fumigation and disinfestation regimes, respectively. Mortality data generated from acute toxicity studies revealed that oil-based Deltamethrin (5%v/v) was more effective (100%) than aqueous solution (53.3%) within similar durations in both chambers. Chlorpyrifos (5%v/v) revealed an acute mortality of 100% for both oil-based and aqueous solutions in both chambers. Residual effect of both Deltamethrin and Chlorpyrifos was dose/time-dependent, with oil-based solution more effective than the aqueous solution. Computed lethal time revealed that LT 50 showed significant difference (P<0.05) between aqueous solution of both insecticidal agents for fumigation treatment. A similar trend was observed for the oil-based solutions of both insecticides in the disinfestations treatment. The implication of this finding in terms of choice of insecticides for acute toxicity and residual efficacy, impact of diluting agents, and sustainable approach to roach control in Nigeria was discussed.

No abstract