Hussein (1991) reported that the use of Tween-80 and Span-80 surfactants as synergistic agents had improved the insecticidal efficacy and lowered the LC50 values from 3.3 to 5 times in case of Cyphenothrin and from 3.2 to 5.7 times in case of fenitrothion. Tween-80 was found more effective than Span-80. The combination ratios between the insecticides and the surfactants are important in determining the insecticidal efficacy.
Abdel-Rahman et al. (1995) evaluated the toxicological effects of five different insecticides (Propoxur, Fenitrothion, D-Phenothrin, Malathion and Permethrin) separately and in combination with two surfactants (Triton X-100 and Tween-20) on Culex pipiens larvae. The results indicated that, the efficiency of the tested chemical insecticides on the bases of their LC50 values could be arranged in descending order as follows: Propoxur > Fenitrothion > D-Phenothrin > Malathion > Permethrin. The used insecticides appeared have high toxicity values against the two tested strains (Abbassia strain and Kashish strain) of Culex pipiens larvae indicating no evidence of development of resistance. Moreover, the addition of three concentrations of the surfactants Tween-20 or Triton X-100 as synergists increase the toxicity of the tested insecticides. The co-toxicity coefficient was concentration dependent.
Bakr (1995) indicated that, the use of two of the common surfactants (Triton X-100 and Tween-20) with IGR's, Bay Sir 8514, Altosid and RO-08-9801 increased the biological activity of IGR's against susceptible and resistant strains of C. pipiens larvae. The use of the surfactants Triton X-100 and Tween-20 as synergistic agent to IGR's improved the insecticidal efficiency and lowered the LC50 values. The results point out the importance of the addition of surfactants (synergistic agent) to IGR's candidates for economical mosquito control in integrated program.
Hussein et al. (2005) they studied the effect of four commercial pyrethroid-based insecticides Cypermethrin, Fenvalerate, Killer and Tyfon super 20 as larvicides against a laboratory strain of Culex pipiens. Kerosene and Tween 80 1% in kerosene were tested as larvicides and pupicides against the same population. The results showed that the mixture of kerosene and Tween 80 could be used as an effective larvicide and pupicide at much lower rates of application compared to kerosene alone, which reduces the environmental pollution to a great extend.
Kamel et al. (2005) evaluated the synergistic action of Tween 80 and Piperonyl butoxide on the larvicidal activities of ethanol extracts of Achillea fragrantissima and Cleome droserifolia and petroleum ether extracts of Cleome droserifolia and Gomphocarpus sinaicus against Ochlerotatus caspius mosquito larvae. The value of synergistic ratio was found greater than one in all the mixtures either with Tween 80 or Piperonyl butoxide.
4. Joint action of plant extracts and insecticide:
Kalyanasundaram and Babu (1982) mentioned that...