George E. Cantwell

Mortality of the honey bee, Apis mellifera, in colonies treated with certain biological insecticides

Abstract Candidate insect pathogens were fed at various levels to honey bees ( Apis mellifera ) either in small cages or in observation hives. The pathogens tested included two polyhedrosis viruses, a granulosis virus, a commercial preparation of Bacillus thuringiensis var. thuringiensis , spores, crystals, and the exotoxin of this variety, plus the crystals of varieties alesti and sotto . No mortality was recorded as a result of treatment with any of these pathogens except with the highest level of the exotoxin of B. thuringiensis .

Evidence for a Novel Insecticidally Active Exotoxin Produced By the HD 116 Strain of Bacillus thuringiensis var. morrisoni

Liquid chromatographic and bioassay data provide evidence for a novel exotoxin produced by the HD 116 strain of Bacillus thuringiensis var. morrisoni. The exotoxin from HD 116 differs from the well known beta-exotoxin produced by the HD 59 strain of Bacillus thuringiensis var. thuringiensis. Chromatograms of aliquots of filtered fermentation broth taken before and after inoculation with the organisms HD 116 and HD 59 were compared. Based on retention times of the obtained peaks, chromatographic fractions were obtained and activity against first instar larvae of the Colorado potato beetle (Coleoptera: Chrysomelidae) was determined. Fractions based upon similar retention times that were active from var. morrisoni were not active from var. thuringiensis and vice versa. Our conclusion that the new exotoxin may be a diphosphate analog of thuringiensin is based on a comparison of relative retention times among several adenine nucleotides. We have tentatively named this new extracellular exotoxin sigma-exotoxin.

THE INTEGRATION OF A BACTERIUM AND PARASITES TO CONTROL THE COLORADO POTATO BEETLE AND THE MEXICAN BEAN BEETLE

Sprays of Bacillus thuringiensis subsp. thuringiensis (B.t.t.), which contained the beta-exotoxin, were applied to small-scale field plots of tomatoes infested with the Colorado potato beetle [Lept...

The histopathological effects of certain carcinogenic 2-fluorenamine derivatives on larvae of the house fly.

Abstract A number of carcinogenic compounds were tested for their effect on the growth and development of larvae of the house fly, Musca domestica. Several carcinogenic 2-fluorenamine derivatives inhibited growth, pupation, and adult emergence and produced focal lesions in the hypodermis, midgut, and fat bodies. These lesions were similar to certain of the hereditary lesions of Drosophila classified by others as tumors or pseudotumors.

Control of the Colorado potato beetle withBacillus thuringiensis varietyThuringiensis

Field tests were conducted to determine the effectiveness of an experimental preparation ofBacillus thuringiensis var.thuringiensis against Colorado potato beetle infestations on potatoes and tomatoes. Applications were made weekly with a tractor-towed commercial sprayer at the rates of either 473, 946, or 2,838 ml. ofB.t.t. in 378.41 of water per 0.4 hectare. Significant reductions were observed in treated plots of all stages of the beetle. All untreated plants were completely defoliated by the end of the test due to beetle feeding. No significant differences were observed among the different treatment levels.

Bacillus thuringiensis a potential control agent for the Colorado potato beetle

In laboratory tests conducted to determine the effectiveness of the exotoxin ofBacillus thuringiensis against the Colorado potato beetle,Leptinotarsa decemlineata (Say), applications sprayed on tomato foliage at dilutions ranging from 10−1 through 10−4 killed 90% of the 1st and 2nd stage beetle larvae. As the dosage decreased, the time to achieve this level of mortality increased from 4 to 9 days. Adult beetles were not killed by these treatments; however they did cease feeding.In field tests, the highest dosages ofB. t. sprayed on either tomato or potato plants provided adequate or nearly complete protection when applied weekly. Young larvae that ingested sub-lethal doses developed into adults with atrophied mouthparts and antennae, transformations of the paired parts of the labial palps into an unpaired part, the appearance of a tarsal-like claw on a palp, and malformation of the cranial sclerities.ResumenSe hicieron pruebas de laboratorio para determinar la efectividad de la exotoxina deBacillus thuringiensis var.thuringiensis (Serotipo 1) contra el escarabajo de la papa de Colorado,Leptinotarsa decemlineata (Say). Las aspersiones sobre el follaje de tomate en soluciones de 10−1 hasta 10−4 mataron 90% de las larvas en 1° y 2° estado. Cuando se redujo la dosis, el tiempo para alcanzar ese nivel de mortalidad se aumentó de 4 a 9 días. Los escarabajos adultos no murieron con estos tratamientos, pero dejaron de alimentarse.En pruebas de campo, las dosis más altas deB.t., asperjadas sobre plantas de tomate o de papa, proporcionaron protección adecuada o casi completa cuando las aplicaciones se hicieron semanalmente. Las larvas jóvenes que ingirieron dosis subletales se desarrollaron como adultos con atrofias en las antenas y partes de la boca, transformación de las partes pareadas de los palpos labiales en partes impares, aparición de una uña como las tarsales en un palpo, y deformación de las escleritas del cráneo.

The World Health organization Kit for the collection and shipment of pathogens and parasites of diseased vectors.

Abstract The contents and directions for using the World Health Organization Kit are described. The kit is available free of charge to all research workers and others wishing to collaborate in WHOs biological control investigations survey. The purpose of the kit is to furnish those participating in this survey a means of preserving and consigning for diagnosis all kinds of pathogens and parasites of any invertebrate vectors of human disease.

Inducement of cytoplasmic polyhedrosis by the intrahemocoelic injection of freed viral particles into the silkworm, Bombyx mori

Abstract Cytoplasmic polyhedrosis was induced 1 by the intrahemocoelic injection of freed viral particles into the silkworm, Bombyx mori. Examination of tissues of the infected insects revealed that formation of the typical tetragonal type of polyhedron was restricted to the gut epithelial cells. The LD50s obtained with preparations of whole intact polyhedra and freed viral particles injected per os and into the hemocoel are compared.

Activity of a “thermostable exotoxin” of Bacillus thuringiensis subsp. morrisoni in the Salmonella/microsomal assay for bacterial mutagenicity☆☆☆

Abstract The purpose of this study was to employ the Salmonella /microsomal assay (Ames test) to investigate the mutagenic potential of a thermostable exotoxin of Bacillus thuringiensis subsp. morrisoni . Bacteria are ideal for the detection of infrequently occurring point mutations because the large number of organisms (200 to 400 million bacteria per plate) exposed to the mutagen at any one time increases the possibility of observing a random mutational event. The exotoxin used in this study was produced using the shaker flask fermentation procedure with mineral casein broth. A Petri dish method of bioassay using fresh bovine feces was used to determine the efficacy of the exotoxin against horn flies. The LD 50 was found to be 5.35 μl/g of feces. Five bacterial tester strains were identified and characterized for the genetic markers described by Ames et al. (B. N. Ames et al., 1975, Mutat. Res. , 31 , 347–364). Appropriate doses of the B. thuringiensis supernatant, solvent or positive control were added to agar plates. The supernatant was tested at five dose levels against all five strains of bacteria. Controls of bacteria only were included for spontaneous reversions. All treatments were performed in triplicate. The numbers of revertant colonies from each set of triplicate plates were averaged and the standard deviation calculated and compared to that found with the solvent control. The negative controls, positive controls, and sterility controls all fulfilled requirements for determination of a valid test. No detectable mutagenic activity was found for the thermostable exotoxin of B. thuringiensis morrisoni .