الفهرس 
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Abstract
The failure of chemical pesticides to continue their
control of insect disease vectors has caused scientists to
turn their attention to the biogenesis of entomocidal toxins
(that is the production of insect toxins by microorganisms).
During the past decade, bacterial larvicides were formulated
commercially for the control of mosquito larvae,
particularly,
insecticidal
Bacillus thuringiensis H-14 and
activity is generally
Bacillus sphaericus. The
associated with a
parasporal crystal produced during sporulation
The effectiveness of these bacterial larvicides under
field conditions is highly dependent on the length of time
the active material remains in the appropriate area. The
persistence of these larvicides under field conditions has
lately been described by several workers, Davidson et al.
1984; WHO (report), 1985; El Sayed, 1988, and many others. It
has been demonstrated that toxicity to mosquito larvae
disappeared after different post-spraying periods depending
on the types of aquatic larval habitats. However, similar
types of larval breeding places, sometimes, gave different
persistence potentials of the applied bacterial larvicides.
Accordingly, a biotic factor was suspected to play a role in
the stability or inhibition of the larvicidal activity which
is the presence of bacteriophages that could lysate the
entomopathogenic sprayed bacteria.