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Effect of artificial and natural plant structures on host searching behavior of the egg parasitoid Trichogramma SPP. (Hymenoptera:Trichogrammatidae)Gingras, Daniel. January 2001 (has links)
No description available.
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Natural spread of and competition between two bacterial antagonists of the fire blight pathogen, Erwinia amylovora, on blossoms of Bartlett pearNuclo, Raymond L. 10 April 1997 (has links)
Graduation date: 1998
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Differential growth of roots and shoots of Douglas-fir (Pseudotsuga menziesii) seedlings infested with Cinara pseudotsugae, and population dynamics of a parasitoid wasp (Pauesia sp.) of C. pseudotsugaeSmith, Julia P. 03 July 1997 (has links)
Aphids are a widespread family of plant pests, whose abilities to suppress shoot
and root growth are well documented for many terrestrial plants. Only a few studies have
been conducted on conifer aphids of the genus Cinara. Cinara pseudotsugae are known
to attack Douglas-fir seedlings, an important crop in the Pacific Northwest. Douglas-fir
are most susceptible to aphid damage as seedlings, especially in nurseries where
conditions favor aphid outbreaks. A parasitoid wasp (Pauesia sp.) attacks C.
pseudotsugae, and may be useful as a biological control agent. Studies of its natural
history and host interactions are needed to assess its potential as a bio-control agent.
This study examined the effects of an experimental range of aphid densities on the
growth of total shoot and root volume and biomass and shoot morphology of Douglas-fir
seedlings. Eighteen-week tests explored short term effects of different aphid feeding
intensities in both the greenhouse and field. Long term effects were tested by exposing
greenhouse seedlings to 16 months of aphid feeding. The ability of the plants to recover
was tested by allowing one set of seedlings to grow aphid free for one year, after being
exposed to aphid feeding for 18 weeks. The success rate of parasitoids over an 18 week
period was compared to aphid density in both greenhouse and field tests.
Increasing aphid destiny was significantly related to decreasing root and shoot dry weights in greenhouse tests. Growth suppression increased slightly during the second year of testing, regardless of whether or not aphid feeding continued. The results for root and shoot volumes were highly variable. However, root tissue density was significantly reduced after the second year of testing. Few shoot characteristics showed consistently significant aphid effects among the trials. Stem diameter and height decreased and needle density of new buds increased significantly with aphid feeding in most tests. Root and shoot growth of field plants did not show any significant aphid effects.
Percentage of parasitoid success was independent of aphid density except at the lowest aphid densities. There was a block effect on parasitoid success in the field test, that may have been a result of varying environmental conditions.
These results indicate that even short term aphid feeding can have long lasting effects on plant growth and structure. The effect on shoot and root growth was small, but there were no signs of recovery. The long term effects of the reduced root tissue density on Douglas-fir is unknown. / Graduation date: 1998
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Effect of soil water pressures on population dynamics of Fusarium equiseti, Glocladium virens, Talaromyces flavus and Trichoderma viride, biocontrol agents of Verticillium dahliae in potatoesHussain, Shaukat 23 February 1994 (has links)
Graduation date: 1994
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Biology, epidemiology, and biological and chemical control of Phytophthora vignaeFernando, W. Gerard Dilantha 04 October 1990 (has links)
Phytophthora vignae, causal agent of stem and root
rot of cowpea (Vigna unguiculata), was reported for the
first time in Sri Lanka. The pathogen was found in cowpea
field soils from 3 of 5 geographic regions sampled. Only
one site however, had plants exhibiting disease symptoms.
Of the eight cowpea varieties grown in Sri Lanka,
four were shown to be relatively resistant; all other
legumes inoculated were completely resistant.
Two morphologic and physiologic races of P. vignae
were identified among the 24 isolates recovered, based on
differential pathogenicity on cowpea varieties.
Bacteria isolated from field soils, and other known
bacterial biocontrol agents, inhibited P. vignae in
culture, but only three Sri Lankan isolates considerably
suppressed the disease in greenhouse tests. Volatile
substances produced by most bacteria inhibited mycelial
growth and sporangial production by P. vignae. The
increased pH of the exposed medium suggested the
involvement of ammonia. Volatile inhibitors were produced
by these bacteria in soil, but only with added substrate;
Strain DF-3101 also reduced oospore germination in soil.
Cowpea plants inoculated with the VA mycorrhizal
(VAM) fungus Glomus intraradices in P. vignae-infested
soil were larger than non-mycorrhizal plants, but only at
low levels of the pathogen. VAM colonization was reduced
at high levels of the pathogen, and root infection by the
pathogen was reduced by VAM.
The fungicides metalaxyl, fosetyl-Al, Banrot, and
Manzate-200DF reduced in vitro mycelial growth, but at
different concentrations. Sporangia formation and
germination, and oogonia formation by P. vignae, was
reduced significantly by metalaxyl and fosetyl-Al. In
greenhouse tests, metalaxyl, even at low concentrations,
reduced disease; Fosetyl-Al was effective at high
concentrations; Manzate-200DF was effective as a soil
drench but not as a foliar spray; Banrot effectively
reduced disease at 50 mg a.i./L. Exposure of a bacterial
biocontrol agent to these fungicides in vitro did not
affect its capacity to subsequently produce volatile
inhibitors, but exposure to 10 ug/ml of metalaxyl and 50
ug/ml of Manzate-200DF reduced its capacity to
subsequently inhibit mycelial growth of P. vignae. / Graduation date: 1991
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The use of heartbeat as a potential screening technique for insect patholgesWare, Mildred G. 03 June 2011 (has links)
Ball State University LibrariesLibrary services and resources for knowledge buildingMasters ThesesThere is no abstract available for this thesis.
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The use of autoradiography in the indentification of selected bacteria in the European corn borerWarn, Beverly Jean 03 June 2011 (has links)
AbstractScientists trying to find biological controls for insect pests are hamperedd by the absence of rapid methods for screening organisms such as bacteria for potential pathogenicity. An organism must grow in the gut of the insect to be pathogenic. By using radioisotopes as tracers a quick method of screening potential insect pathogens may be developed.Escherichia coli and Sarcina flava were used as known nonpathogens and Bacillus thuringiensis was used as a known pathogen. In this work an attempt was made to verify the presence of bacteria in specific tissues of the insects.European corn borer larvae were fed 1-C14 palmitic acid and labeled E. coli, S. flava and B. thuringiensis. Parasaggital sections were made of the corn borers and radioautograms were made of the sections. Grain counts over a 2,000 u2 area were made of various tissues and compared.There was a statistically significant difference in the distribution of label in corn borer larvae fed labeled bacteria as compared to corn borers fed 1-C14 palmitic acid. Label tended to incorporate into fatty tissue in the corn borers.If this technique can be used to positively demonstrate the establishment of selected bacteria in the gut of the insect then it may be possible to use such methods to screen for potential insect pathogens and give insight into the mechanisms which result in the death of insects.Ball State UniversityMuncie, IN 47306
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Effect of artificial and natural plant structures on host searching behavior of the egg parasitoid Trichogramma SPP. (Hymenoptera:Trichogrammatidae)Gingras, Daniel. January 2001 (has links)
Differences in plant structure and host abundance, distribution and density within and between plants may affect host finding success of searching parasitoids. The main objective of this research consisted in developing and validating a model that can predict parasitism by Trichogramma evanescens on various plant structures. Also, we evaluated the effect of both artificial and natural plant structures on host encountering success and on searching behavior of two species of Trichogramma. / Size (S), heterogeneity (H) and connectivity (C) define plant structure. The development of the model of parasitism was based on laboratory experiments using three dimensional artificial plants of different combinations of S, H and C. The model was then validated with experiments, within greenhouse, using natural cruciferous plants of different structures. Significant regressions of observed values of parasitism as a function of those predicted by the model were obtained. / The effect of plant structure on two species of Trichogramma was studied by using three species of Lepidoptera and three structurally different but closely related crucifers. Also the distribution pattern of parasitized eggs according to leaf side and plant height was characterized. A repeated measure ANOVA in time where plant ages defined the repeated measures showed that all three main effects (plant, host, parasitoid) had significant effect on parasitism and only the parasitoid x plant structure interaction was significant. Mean percent of parasitism was higher on cabbage, intermediate on broccoli and lower on Brussels sprouts whereas cabbage appeared to be intermediate in plant structure, broccoli appeared to be the most simple and Brussels sprouts the most complex plant structure. On simple plant structure, both wasp species performed well on the three varieties of plant but T. evanescens outperformed T. pretiosum more often on the various plant structures. A doubly repeated measures ANOVA in space revealed significant effects of leaf side and plant height on parasitism, being greatest under leaf surface and at the base of the plant. The interaction between those two variables was not significant. / The effect of plant structure on searching behavior of T. evanescens was determined by direct observation of individual females searching on simple and complex plant structures during 1 hour. Time, frequence and sequence associated to activities and plant parts explored were obtained and analyzed. Plant structure had significant effect on time budget associated to activities (walking, resting, flying) and plant parts explored. / This study demonstrates that plant structure mediates ecological interactions by affecting host finding success and this may have important implications in population dynamics, evolution of hosts and parasitoids but also in biological control programs.
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Attitudes of Quebeckers toward environmentally related outdoor activities and agricultural pest control.Clark, Robert G. January 1979 (has links)
No description available.
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Evaluation of strains of Bacillus thuringiensis as biological control agents of the adult stages of the carrot weevil, Listronotus oregonensis (Coleoptera:Curculionidae)Saade, Fabienne Eugenie Joseph January 1993 (has links)
Strains of Bacillus thuringiensis active against Coleoptera were evaluated for toxicity against the adult stage of the carrot weevil, Listronotus oregonensis. Mortality and frass bioassays using a suitable semi-artificial diet showed strains A30, A429 and BTT to be highly toxic. Mortality persisted after initial exposure to the bacteria with the survivors not resuming normal feeding. Attempts to reisolate B. thuringiensis from the insects revealed B. thuringiensis-like organisms in the gut and in/on other structures. At the midgut pH of the insect (pH 8.0), the crystals of the toxic strains were significantly more soluble in vitro than were crystals of the less toxic strain A311. Proteolytic activation of the crystals with gut extracts yielded a protein band (66-67 kDa) for strains A30 and A429 which was similar to he apparent molecular weight of the toxin protein for BTT. Evidence suggests that the low toxicity of strain A311 might be due, in part, to the absence of the toxic moiety of the $ delta$-endotoxin.
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