No abstract

Biochemical approaches have been used to enhance the potency of Bacillus thuringiensis against Plodia interpuneteUa. Tests were made with different classes of chemical compounds, characterizedby being safe, non-toxic to man, and cheap in price. Among the tested inorganic salts, calcium carbonate, calcium oxide and zinc sulphate were found to increase the potency of B. thuringiensis 5-endotoxin by 23-, 1.9-and 2.7-fold, respectively. With the nitrogenous compounds, the amlno acids serine, arginine, alanine and leucine enhanced theendotoxin effect by 5.2-,3.6-, 1.3and 1.1-fold, respectively. Also, among the protein solubilizing agents, EDTA and sodium thioglycollate led to a 100-and 2.6-fold increase in the potency. Formic acid was highly effective among the organic acids used in enhancing the potency, followed by malic acid, with 44$-and 2.4fold increase, respectively.Resume-Une approche bio-medical a e"te" utilise' pour ameliorer la puissance de Bacillus thuringiensis contre la mitte Indienne Plodia interpuneteUa. Des analyses ont iti faites avec des classes de composition chimique characterise" par leur aspect sain. Entre les sets analyses le carbonate de calcium et I'oxide de calcium et la sulphate de zinc ont augments la puissance de B. thuringiensis 5-endotoxin par 2,5,2,7 et 1,9, respectivement Avec les composition (azotique) les acide amino, la serine, I'arginine, I'alanine et le leucine ont ameliore I'effet par par 5,2,3,6,1,1 et 1,3 respectivement Aussi avec les agents de solubilisation de proteine, EDTA et le thioglycollate de sodium ont augments la puissance par 100-et 2,6 fois. L'acide fourmique a ete tres efficace parmi les acides organiques qui ont 6t6 utilise pour ameliorer la puissance suivi par I'acid malic par 4 3 et 2,4 fois, respectivement

The spore-endotoxin preparations of some 23 cultures of B. tburingiensis were screened with respect to their activities against the Indian meal moth Plodia intevpunctella and angoumois grain moth Sitotroga cerealella. The highest activity against both insects was recorded for the variety dendrolimus HD-34 and the factors of increase were 60 and 9, respectively, compared to that of the standard. The larvae of angoumois grain moth were highly susceptible to varieties kurstaki, tolworthi, galleriue, entomocidus and aizawui. Varieties kyushuensis and tbompsoni were potent against angoumois grain moth but, on the other hand, they showed little activity against the Indian meal moth. The extent of potency of the different varieties of B. t. depends upon the isolate itself rather than on the varieties of the serotype.

The present study was initiated to compare the histopathology of two isolates of Bacillus thuringiensis (subsp. indiana and subsp. morrisoni), in the larval tissues of Plodia interpunctella (Hübner) and Tribolium castaneum (Herbst). Most changes were localized in the midgut. Other effects were observed in muscles and tracheoles. In P. interpunctella, larvae were treated with a lethal dose of 500 g of B.t. subsp. indiana/g of grains. Changes appeared in midgut cells 8 h after treatment. At 24 h after treatment, cytoplasmic vacuolization was observed in the basal part of cells. Swollen epithelial cells were accompanied by swelling of the nuclei of columnar and goblet cells. The nuclei of the columnar cells were pycnotic and the membraneous sheaths were completely ruptured. The mitochondria had vacuoles 2 h after treatment followed by complete lysis 24 h after treatment. The circular and longitudinal muscles showed relaxation and disintegration of their fibrils and mitochondria. In T. castaneum, larvae were treated with a lethal dose of 5000 g of B.t. subsp. morrisoni/g of grains. Changes appear in the regenerative cells, where cytoplasmic vacuolization and pycnotic nuclei were observed. The tracheal cells showed relaxation of the taenideal cuticular lining and disintegration of mitochondria and chromatin clumping granules around the nuclear membrane 48 h after treatment. Seventy-two hours after treatment, the tracheal and circular muscle fibers showed complete relaxation. The two varieties of B.t. that were collected from grain dust in Egypt, have potential as control agents for stored-product moths and beetles. The toxic action differs in the two tested insect species.