Bibliography: leaves 170-189. This thesis looks at aphid feeding determinants by type and location. It examines the role of leaf surface chemicals in the discrimination of host plants and the deterrent effect of catechin and its oxidative condensation products.

Bibliography: leaves 170-189. / xi, 189 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis looks at aphid feeding determinants by type and location. It examines the role of leaf surface chemicals in the discrimination of host plants and the deterrent effect of catechin and its oxidative condensation products. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1992

Four sampling techniques were evaluated to estimate clover aphid, Nearctaphis bakeri (Cowen), abundance in red clover fields in the Willamette Valley. The Berlese funnel method detected one to four times more aphids than other sampling techniques. Visual assessment often underestimated the high aphid densities during the flowering and seeding of clover. Sweep net and Schuh shaker techniques had limitations and underrated the numbers of aphids present in the clover fields. Strong correlations (r² = 0. 74 - 0.87) were found between the Berlese funnel technique and visual assessment technique in a 2nd year established field. Numerical differences in the spatial distribution of N. bakeri on clover stems were shown during various stages of plant development over the season. During development of buds and axils, aphid numbers on the lower half of the plant averaged 1.5 times greater than those on the upper half. As the season progressed into the flowering and seeding stage, aphid numbers on the upper stem halves were approximately five times greater than those on the lower half. Winged clover aphids were too few to show definite peaks of flight using water traps, averaging 2.19 aphids per yellow bucket during the June-August period. No significant differences in aphid attractiveness to the different colors were found among water pan traps. Yellow buckets captured approximately five times more alate aphids than did yellow, red, or green pan traps. Traps placed on the south side of the field contained higher numbers of aphids than in other locations in the red clover fields. / Graduation date: 1991

Two independent experiments were conducted during 1992 and 1993 using a Randomized Complete Block Design with four replications. The first experiment was designed to study the effect of mulch spectral properties on weed growth and development. The second was conducted to study the effect of polyethylene mulch on aphid population and on growth and yield of bell pepper. Initially, rye-grass germination under polyethylene mulches was significantly higher than that on bare soil, whereas mustard seed germination under mulches did not differ significantly from that on bare soil. However, at the end of 30 days, none of these weeds were observed in the mulched plots. Transmittance, reflectance, and absorbance were recorded in the Near Ultraviolet (390-399 nanometre), Photosynthetically Active Radiation (400-700 nanometre), and Near Infrared (701-1100 nanometre) bands for black, black microperforated, wavelength selective and silver mulches. Aging had little effect on the optical properties of the mulches. The wavelength selective (Infra red transmitting = IRT-76) green mulch had the warmest mean soil temperatures, followed by silver, black, microperforated black mulch, and bare soil. The soil moisture content was higher under plastic mulches than in bare soil. The use of mulches significantly increased both the early and total marketable yields of pepper. Plants grown with polyethylene mulch had significantly lower number of aphids on them than did their bare soil counterparts.

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Doctorat en Sciences / info:eu-repo/semantics/nonPublished

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The probing behavior and feeding activity of green peach aphid, Myzus persicae Sulzer, on Bacillus thuringiensis ssp. tenebrionis- transgenic potatoes, insecticide treated potatoes, and host plants with different preference were electronically monitored. I found that first, transgenic potatoes had no effect on green peach aphid probing suggesting that transmission of green peach aphid-borne viruses would not be affected. Second, the probing behavior of green peach aphid was not modified by the insecticides, aldicarb, Admire, and Di-syston. However, the postfeeding behavior of aphids was different over time and with insecticides, which might have an influence on virus transmission in the field. Third, the probing behavior of green peach aphid on host plants with different preference varied. Aphids probed more when they moved from a higher-preference host plant (radish) to a lower preference host plant (potato). In addition, the settling rate was low when aphids were moved from higher to lower preference host plants. This difference might affect virus transmission in the field. Vector efficiency, relationship of virus transmission between vector and host plants, and vector control strategies are discussed. In addition, the probing behavior of two mosquito species, Aedes aegypti and Anopheles stephensi, on mice was recorded electronically to examine waveform patterns and to quantify sporozoite output. My studies indicated that sporozoite output of malaria-infected mosquitoes was not detected by using the electronic monitoring system. The relationship between waveform patterns and penetration activities of mosquitoes needs clarification before further studies can be conducted. / Graduation date: 1994

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