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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Factors influencing the control of citrophilous mealybug Pseudococcus calceolarie (Maskell) by Coccophagus gurneyi Compere in the Riverland of South Australia /

Alfaro Lemus, Ana Lilia. January 2001 (has links) (PDF)
Thesis (M.Ag.Sc.)--University of Adelaide, Dept. of Applied and Molecular Ecology. / Includes bibliographical references (leaves 102-114).
12

Preliminary evaluation of the rice blast fungus (Magnaporthe grisea) as a potential bioherbicide control agent for crabgrass (Digitaria sanguinalis) infestations of tall fescue (Festuca arundinacea Schreb. cv. Fawn) turf

Williams, Donald L. January 1998 (has links)
This study addressed the possibility of rice blast fungus (Magnaporthe grisea) as a potential bioherbicide for the control of crabgrass (Digitaria sanguinalis), in turf/lawn plantings. Experiments were: (i) evaluation of the effect of bioherbicide inoculum dosage (titer) on disease severity in crabgrass; (ii) competition between crabgrass and tall fescue (Festuca arundinacea Schreb. 'Fawn') and the additive effect of rice blast bioherbicide on the competitiveness of crabgrass; (iii) survival of rice blast spores under non-conducive infection conditions on crabgrass; and (iv) effect of multiple inoculations of rice blast fungus and subsequent disease on crabgrass.Spore concentrations of 5 x 105 to 1 x 106 conidia/mI had no significant difference in effect on mean biomass reduction of treated crabgrass. All produced tissue death and loss of vigor in treated crabgrass, but no plant death. In one trial, a spore concentration of 2 x 106 conidia/ml produced 100% biomass loss in treated crabgrass.Competition studies indicated crabgrass will out-compete fescue 'Fawn' in plots of equal numbers of each plant, i.e., 3 fescue and 3 crabgrass. In 10 x 10 cm mini-lawns of fescue interspersed with 5 crabgrass plants, fescue will out-compete the crabgrass. In mini-lawns of fescue and crabgrass, infection of crabgrass with non-lethal doses of rice blast fungus improved fescue's ability to out-compete crabgrass. Three methods of investigating competition were tested. Mini-lawns sown with 0.5 g fescue seed (approx. 200 seeds) with crabgrass seed sown into centers of the four quadrants and in center of the mini-lawn, worked best.Survival of Magnaporthe grisea conidia under non-conducive conditions was tested by drying inoculated crabgrass seedlings for 0-48 hours prior to dew-deposition. Treatments verified spores remain viable at least 24 hours on crabgrass leaves under greenhouse conditions (25-40° C and 25-75% relative humidity).Two successive inoculations (at 3 days and 7 days after primary inoculation) of crabgrass with M. grisea conidia (5 x 105 conidia/ml) resulted in significant reduction in growth compared to a single spore application.Results suggested Magnaporthe grisea exhibits potential for future development as a commercial bioherbicide to control crabgrass (Digitaria sanquinalis). Current studies investigated integration in lawn grass, but should be applicable to situations anywhere crabgrass is considered a weed e.g., in corn (Zea mans) or soybeans (Glycine max). / Department of Biology
13

Characteristics of Typhlodromus americanus Chant and Yoshida-Shaul (Acari: phytoseiidae) as a biological control agent of Oligonychus ununguis (Jacobi) (Acari: tetranychidae)

Horton, Rene N. 05 June 1995 (has links)
The life history, temperature, humidity, and feeding requirements of the phytoseiid predator mite, Typhlodromus americanus Chant and Yoshida-Shaul were tested in the laboratory. Occurance of the mite in the field during different times of the year was investigated as well. Effects of temperature and humidity on egg hatch, the feeding requirements of the larvae, the amount consumed by each life stage, the length of each life stage and suitability of different food sources were investigated in the laboratory. The use of the mite as a biological control agent was evaluated by using the information gained from the laboratory experiments. T. americanus was originally discovered in plantation grown Douglas-fir in western Oregon. Since that time the mite has been found on a number of other hosts throughout North America. The mite is active year round in the Christmas tree plantations of the Willamette Valley in Oregon. The adult is found in or near the one year old bud scars and the eggs are typically deposited there also. Life parameters were measured providing a net reproductive rate of 4.23, a mean generation time of 24.45 days, and an intrinsic rate of increase of 0.059 The intrinsic rate of increase was low when compared to other predator mites and numerical response to prey increase would not be possible with such a low rate. The optimal temperature for the shortest eclosion time (54.4 hr.) and the highest survival (96.4%) was 26��C. The regression of temperature vs. time to hatch gave a 90% R�� with both the slope and intercept significantly different from zero. Humidities above 70% had survival rates over 96% and eclosion rates in the range of 50-58 hours. The relative humidity at which 50% of the population died was 58.6%. The mite was found to feed readily on the pest mite Oligonychus ununguis (spruce spider mite), as well as Tetranychus urticae (two spotted spider mite), and corn, oak, and Douglas-fir pollens. The larval form of the predator mite does not require food to molt to the protonymph, but the protonymph does require food to molt. If water is provided the entire time from egg to death, the protonymph can survive about ten days. Females consumed more Tet. urticae than males in both the immature and adult stages. The T. americanus that were fed corn pollen and Tet. urticae (complete diet) lived for over 115 days. Mites raised on oak and corn pollens did not survive as long (only 70-80 days), and those raised on Douglas-fir pollens did not reach adulthood. Egg production was observed on the complete diet, but not on the diets of pollen. The largest number of eggs were laid around the twelfth day after the molt to adult. Control and management of field conditions to improve habitat for T. americanus will be the best approach for its use as a biological control agent. As it does not respond numerically to prey increase, it will be more effective in a regulatory role to prevent these increases while the prey is at low levels. / Graduation date: 1996
14

Improvement of biological control agents : laboratory selection for fast larval development in the convergent lady beetle, Hippodamia convergens guerin-M��neville (Coleoptera: Coccinellidae)

Rodriguez-Saona, Cesar Ramiro 09 June 1994 (has links)
Hippodamia convergens Guerin-Meneville was selected for rapid development through five generations at four constant temperatures (18, 22, 26, and 30��C). Two levels of selection were used: intense and moderate. Differences in developmental rate, survivorship, live adult weight, aphid consumption, adult longevity, and fecundity were measured for both groups and an unselected line. The two selected lines exhibited significant differences in developmental rate after the first generation of selection. The differences increased by the fifth generation of selection. Average differences between selected lines at 18, 22, 26, and 30��C in development from egg to adult were 4.9, 3.0, 1.0, and 1.5 days, respectively. Individuals from the intense selected line had a lower developmental threshold (11.3��C) than the moderate selected line (12.0��C). Also, degree-day requirements from egg to adult were lower in the intense (266 DD��) than moderate (277 DD��) line. Wild type beetles accumulated 231 degree-days above a threshold of 13.6��C. Survivorship at cold temperatures significantly increased with selection for fast development. In addition, no significant differences occurred in either live adult weight, total larval consumption of prey, fecundity, or adult longevity. Larvae selected for fast growth consumed higher numbers of aphids per day and were more efficient metabolically in converting prey mass into body mass than slow growing larvae. Because of a lower developmental threshold and lower degree-day requirements, for complete development, beetles from the intense selected line may accumulate more degree-days throughout a year compared to a moderate selected line. Predictions of population growth, based on an equation for intrinsic growth rate, showed that beetles from the intense selected line would produce 1.6 and 1.4 times more individuals in a 60-day period than beetles from the moderate selected and unselected lines, respectively. The results suggest that intense selected beetles would develop faster earlier in the season and would produce higher population numbers under optimum conditions. Thus, selection of H. convergens produced superior beetles for future introductions in biological control. / Graduation date: 1995
15

Biological control of spider mites by the predatory mite Neoseiulus fallacis (Acari: Phytoseiidae) in ornamental nursery systems

Pratt, Paul D. 16 September 1999 (has links)
We identified and evaluated a phytoseiid predator as a biological control agent of multiple spider mites pests that occur in ornamental nurseries. When comparing species, Neoseiulus fallacis (Garman) had a wider prey range than Galendromus occidentalis (Nesbitt), a higher probability of overwintering than Neoseiulus califomicus McGregor and was equally or more effective at suppressing spider mites than either of the other 2 phytoseiids in 4 field tests. To further evaluate N. fallacis we 1) measured prey range when held with 29 ornamental pests or alternative foods under laboratory conditions, 2) tested biological control of spider mites on representative plant species at both small and large spatial scales, 3) developed release and conservation strategies of the predator, and 4) examined the efficacy of the predator in controlling recently introduced pests. Neoseiulus fallacis had greatest survival and reproduction when feeding on spider mites but eriophyid mites, other mites and pollen enhanced survivorship and, in some cases, reproduction. When inoculated into ornamental plants, spider mite suppression was "acceptable" in 81% of small scale tests and-in all large scale tests. Limitations in control occurred in tall, vertical growing plants with little foliar canopy. Inoculation of N. fallacis at low prey densities into apple rootstocks was successful at suppressing Tetranychus urticae Koch and similar to control achieved at moderate prey densities. In small scale banker plant studies, high densities of adult and immature mites of N. fallacis were produced and moved downwind to receiver plants. In field tests with receiver plants placed at greater distances, only N. fallacis adult females readily dispersed to 30 m or more. When comparing overwintering survival of adult females among plant types, N. fallacis survived most on conifers, intermediate on evergreen shrubs and least on herbaceous perennials, deciduous shrubs and shade trees. Covering plants with protective plastic reduced overwintering survival of the predator. Neoseiulus fallacis successfully suppressed the newly introduced pests Panonychus citri (McGregor) and Schizotetranychus celarius (Banks) on Skimmia japonica Thunberg and Sasaella hidaensis (Makino and Uchida), respectively. Initial studies suggest that N. fallacis can be an effective biological control agent of multiple spider mites in low-growing and selected higher-growing ornamental plants. / Graduation date: 2000
16

Inhibitory properties of microplitis croceipes teratocyte secretory products and the recombinant protein TSP14 on protein synthesis

DiLuna, Francis Anthony. January 2003 (has links) (PDF)
Thesis (M.S.)--University of Kentucky, 2003. / Title from document title page (viewed June 21, 2004). Document formatted into pages; contains xii, 122 p. : Ill. Includes abstract and vita. Includes bibliographical references (p. 106-121).
17

Laboratory and field host utilization by established biological control agents of Lantana camara L. in South Africa /

Heystek, Fritz. January 2006 (has links)
Thesis (M. Sc. (Zoology and Entomology))--Rhodes University, 2006.
18

Potential antifouling compounds of marine-derived fungi from Hong Kong /

Miao, Li. January 2006 (has links)
Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.
19

Potential antifouling compounds of marine-derived fungi from Hong Kong

Miao, Li. January 2006 (has links)
Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Adviser: Pei-Yuan Qian. Includes bibliographical references.
20

Predator interactions within a trophic level : Phalangium opilio L. (Arachnida: Opiliones) and mites (Arachnida: Acari) : a thesis submitted in partial fulfilment of the degree of Master of Applied Science at Lincoln University /

Merfield, C. N. January 2000 (has links)
Thesis (M. Appl. Sc.) -- Lincoln University, 2000.

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