Production of Culex pipiens (Dip.: Culicidae) adults infected by Strelkovimermis spiculatus (Nematoda: Mermithidae) in autodissemination control strategy

Biological Control of mosquito vectors with insect parasitic nematodes is of importance in Integrated Mosquito Management (IMM) due to its benign nature. The mosquito parasitic mermithid Strelkovimermis spiculatus normally parasitizes larval stages of Culex pipiens and rarely do adults of Culex get infected by this nematode in wild. This infrequent phenomenon is assumed as the way of nematode dispersal. We hypothized that infected mosquito adults can be obtained through laboratory manipulations. Parasite: host ratio and host stage were two main parameters to consider. To determine the optimal larval instar and parasite:host ratio, late third, early fourth, late fourth instar larvae and 5:1, 10:1, 20:1, 40:1 ratios were compared and the percentage of infected adult mosquitoes obtained recorded. Average nematode emergence time was measured to to estimate the proper release time of the mosquitoes in larval habitats. The sex ratio, number and length of postparasites emerged from adults were also calculated and compared in quality control process. Only late fourth instars infected adult host at 5:1 with a maximum proportion of infected adults of 17.39%. The ratio of 10:1 was chosen as standard infection ratio (P=0.87). The average duration between infection and nematode emergence was 7.37±0.51 (days). The proportion of females to total emerged nematodes from adults was 0.4:1 which is an acceptable ratio for nematodes’ colonization in water bodies. There was no statistical difference between the length of nematodes emerged from mosquito adults and larvae (P=0.14). Infecting late fourth instars individually at 10:1 infection ratio in an aliquot of nematode suspension and release of infected males seven days post-infection is a feasible strategy for application of this nematode in wild.