Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 67-71).

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The effects of pathogens, used singularly or synergistically with other pathogens on the European corn borer larvae, Ostrinia nubilalis (Hubner), were studied. Pathogens used in this research were Perezia fumiferananae, Nosema disstriae, Nosema bombycis, Bacillus thuringiensis, and Beauveria bassiana. The egg masses were dipped into a vial containing a suspension of a single pathogenic species or combination of two pathogenic species. The egg masses were then incubated and hatched in a growth chamber with a temperature of 29°C, a relative humidity of 639, and constant light conditions. Observations were made concerning the mortality rates of each pathogen group.It was observed that the known pathogens, Bacillus thuringiensis, and Beauveria bassiana, caused high mortality rates in the corn borer larvae and could serve as effective biological controls. The Microsporidia, Perezia,fumiferanae, Nosema disstriae, and Nosema bombycis caused low mortality rates in corn borer larvae and therefore would not be considered as effective biological control agents for the European corn borer.The mortality rate for Bacillus thuringiensis treated larvae or Beauveria bassiana treated larvae, used in combination with other Microsporidia was not as high as when Bacillus thuringiensis,or Beauveria bassiana was used singularly. There may have been some interference or antagonism between the two combined pathogens, whether these pathogens be fungi, bacteria, or microsporidia.

The use of Clostridium species as possible pathogens of the European corn borer, Ostrinia nubilalis (Hubner) was arrived at by using screening criteria derived from studying the environment of the insect mid-gut and correlating these criteria to known physiological factors of bacteria. European corn borer larvae were treated by placing one drop of bacterial suspension on a corn borer egg mass. The newly-hatched larvae were then transferred to sterile, individual vials with synthetic food medium and observed daily. Clostridium putrefaciens (McBryde) treated larvae showed a significant reduction in hatching, slowed growth rate and a mortality of 50%.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed April 26, 2007). PDF text: v, 109 p. : ill. UMI publication number: AAT 3229553. Includes bibliographical references. Also available in microfilm and microfiche formats.

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The purpose of this study was to compare the pathology caused by two bacterial species, Bacillus subtilis and Bacillus thuringiensis, in European corn borer larvae. The study consisted of: (1) a determination of the mortality of larvae that had ingested various concentrations of bacterial spores; (2) light microscopic examination of midgut tissues of larvae treated with various concentrations of bacterial spores, and (3) examination of midgut tissues of treated larvae with transmission electron microscopy.The results of the mortality study indicated that B. subtilis did not cause mortality in corn borer larvae. Light and electron microscopy did not reveal any pathological damage to midgut tissues of larvae treated with B. subtilis. It was observed that there was an increase in the amount of peritrophic membrane produced in the larvae treated with B. subtilis. These larvae were also observed to be sluggish and have diahrrea, suggesting a mild disease state.Mortality in larvae treated with B. thuringiensis varied with the concentration of spores ingested, and ranged as high as 100 percent. The mortality data were used to select three spore concentrations, corresponding to 25 percent, 50 percent, and 90 percent mortality levels. Larvae treated with B. thuringiensis spores in these concentrations were then examined by light microscopy. The pathology observed included slight swelling and vacuolation of the epithelial cells, cellular disruption, and complete breakdown of the epithelial tissue and subsequent bacteremia. It was observed that the degree of pathology increased with an increase in the bacterial spore concentration.Electron microscopic examination of midgut of B. thuringiensis treated larvae revealed the following pathological symptoms: decrease in apical microvilli, decrease in microvilli of goblet cells, and decrease in basal infoldings of plasma membrane.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Charles E. Mason, Dept. of Entomology & Wildlife Ecology. Includes bibliographical references.