Effect of bacteriophage lysogeny on the efficacy of two bacterial larvicide formulations under field conditions

ABSTRACT

Two types of man-made ditches were selected for carrying out this experiment; one polluted with nitrogenous matters [sewage water] and second filled with accumulated irrigated clear non-chlorinated water. No phages were detected in samples collected from both types of ditches. However, phage[s] specific to only B. sphaericus was [were] detected after spraying the two types with both B. thuringiensis H-14 and B. sphaericus commercial formulations. The detection of phage[s] was observed after three days post-spraying in the polluted ditch and after one week in the non-polluted one. This observation was explained by a possible transduction of naturally existed phage[s] on other spore forming bacteria to the sprayed B. sphaericus only, as its commercial formulation is based on spores which germinate to produce vegetative cell, while B. thuringiensis H-14 contains only the O- endotoxin as active ingredient, and also due to the increase of the number of bacteria in the sprayed ditches due to the recycling of B. sphaericus in the aquatic breeding places