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—Bacillus thuringiensisH-14 (Alex), originally isolated from moribund and dead larvae of the casuarina stem borer, Stromatium fulvum, was tested in the laboratory against the second and fourth-instar larvae of both mosquito species, Aedes aegyptiand Culex pipiens.The pathogenicity of this bacillus was established when both insects were found to be susceptible to infection over the whole range of test concentrations (0.005–0.35 mg/1). However, A. aegyptishowed a higher degree of susceptibility to B. thuringiensisH-14 (Alex) than C. pipiens.A mortality of 100% was achieved within 24 hr with concentrations of 0.09 and 0.25 mg/1 for second- and fourth-instar larvae of A. aegypti, respectively. Also, younger larvae of both test mosquito strains were more susceptible than mature ones. —Bacillus thuringiensisH-14 (Alex), original isolée de larvés morte et de tige de casuarina stem borer, Stromatium fulvum, on a fait une expérience en laboratoire contre les larvés de II et IV stade à deux différents espèces de moustiques qui sont Aedes aegyptiet Culex pipiens.On à prouvé que la stabilité du bacillus contre les maladies que chaque espèces de moustiques étaient sensibles contagé à la maladie dans toutes les concentrations (0.005–0.35 mg/1). On à prouvé que A. aegyptiétait plus sensible a B. thuringiensisH-14 (Alex) que C. pipienson a obtenu 100% de taux de mortalité en 24 hr dans les concentrations 0.09 and 0.25 mg/1 a la II et IV stade larvés respectivement pour A. aegypti, mais 0.15 et 0.35 mg/1 et ce qui employé pour C. pipiensà la II et IV stade larvés respectivement. Aussi les petites larvés d’un âge plus petit était plus sensible que les larvés ageés.

Average yields of Mattesiaspores (spore productivity) had varied from a minimum yield (0.17 ×107spores) for Laemophloeus turcicusadult to a maximum yield (7.46 ×107spores) for Plodia interpunctellalarva. Comparatively, the highest increase in Mattesiaspore yield, recorded from P. interpunctellalarva (7.46 × 107spores) over the lowest one, estimated for L. turcicusadult (0.17 ×107spores), was nearly 44-fold. The increase in Mattesiaspore yields that calculated from the other hosts (P. interpunctellapupa or moth; Galleria mellonellalarva; Rhyzopertha dominicaadult; Sitophilus zeamais), over that estimated for L. turcicusadult, was less than 10-fold (6–9-fold). Based on the weight of 1 g of the insect host infected with Mattesiasp., small stored grain insect hosts (e.g. L. turcicus, S. zeamais, and R. dominica) seemed to achieve Mattesiaspore yields more than the larger ones (e.g. P. interpunctella). The increase in spore yields over that used for the inoculum, based on an average of 25 P. interpunctellalarvae per bioassay container, was ca. 2 to 31-fold. These results revealed that the Indianmeal moth, P. interpunctella, could serve as a potential host for mass propagating the isolated entomopathogenic protozoan, Mattesiasp. Besides Mattesialarval mortality, survivors of Mattesiainfection suffered deformities and noticeable undersized pupae or adults than the control ones. Also, many copulated moths (ca.46%) were unable to become separated after copulation until they had died. Bioassay of siftings, obtained from L. turcicus-protozoan-infected stock cultures, was carried out in order to emphasize the suppressive potent role of such protozoan entomopathogens in long-term storage. With the highest tested concentration of the studied siftings (10%), mortality responses due to Mattesiainfection ranged from 13 to 68% at 14–169 days post-treatment. The corresponding figures for Adelinainfection were 7–42%.