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A twelve-month survey for mosquito predators was conducted in Townsville, Queensland, Australia, which is located in the arid tropics. The survey revealed the presence of five predaceous insects but only Anisops sp. (backswimmers) and Diplonychus sp. were common. Predatorial capacity and factors influencing this capacity were then assessed for adult Anisops sp. and adult and nymph stages of Diplonychus sp. against Culex annulirostris mosquito immatures under laboratory conditions. Predatorial capacity bioassays showed that adult Diplonychus sp. preyed upon both larval and pupal stages of Cx. annulirostris quite successfully. Nymphs of Diplonychus sp. proved to be more successful with smaller prey immatures, and Anisops sp adults did not prey successfully on any prey pupae. Increasing the foraging area and introducing aquatic vegetation significantly reduced the predatorial capacity of Diplonychus sp. nymphs, while only vegetation and not foraging area had a significant effect on adult Diplonychus sp. predation capacity. Overall, adult Diplonychus sp. proved to be a more efficient predator than Anisops sp., and field trials are now recommended to further assess the potential of Diplonychus sp. as a biocontrol agent.

The failure to discover a significant new class of insecticides has led many researchers back to biodiscovery studies in the search for new and economically viable alternatives. After a preliminary screening of botanical extracts using descending series of concentrations (1,000, 500, 100, 50, and 5 mg/liter), 8 extracts from 2 potential botanical agents, Khaya senegalensis (Desrousseaux) and Daucus carota L., were tested against 4th instars of Culex annulirostris (Skuse) following the standard World Health Organization insecticide susceptibility methodology. The median lethal concentration (LC50) values for K. senegalensis against Cx. annulirostris using acetone, ethanol, hexane, and methanol extracts were 20.12, 5.1, 5.08, and 7.62 mg/liter, respectively. The LC50 values for D. carota against Cx. annulirostris using acetone, ethanol, hexane, and methanol extracts were 236.00, 36.59, 77.19, and 241.8 mg/liter, respectively. Extracts from K. senegalensis were more potent than those from D. carota against Cx. annulirostris and hexane and ethanol were the best solvents to extract essential oils from both plant species, respectively. In potency, K. senegalensis was similar to azadirachtin, but fractionation and compound isolation of the hexane extract in particular may reveal a potent phytochemical that could be compared to synthetic mosquitocides.

No abstract

Field and laboratory studies were carried out during two successive summer seasons in order to study the susceptibility of the different tested cantaloupe cultivars namely (Ideal, E81-065, Mirella ,Vicar, E81-013 and Magenta) to infestation by Thrips tabaci, Bemisia tabaci and Tetranychus urticae. Field studies were carried out during the two consecutive growing seasons (2006 and 2007). There were significant differences in the susceptibility of cantaloupe cultivars to infestation by these pests. These mentioned that, E81-065 and Magenta cultivars were the lowest infested ones by these pests. On the other hand, Mirella variety was the highest infested cultivar. To give a spot light on the reason of the differences in the susceptibility of the tested cantaloupe cultivars, chemical analysis of the dried leaves were carried out during growing season of 2007. Chemical analysis of infested leaves showed correlation between certain phytochemical components (organic and inorganic compounds); reduced, non-reduced and total sugars, potassium, total protein, carbohydrate, and phosphorous as well as moisture content and population density of T. tabaci, B. tabaci and T. urticae.