Intra- and interplant movement and dispersal of the predator mites Neoseiulus californicus (McGregor) and Neoseiulus fallacis (Garman) were studied on both lima bean (Phaseolus lunatus L.) and apple (Malus pumila Miller) branch plant systems that were seeded with excess numbers of the spider mite Tetranychus urticae Koch. Individuals of either predator were randomly selected from colonies of well-fed, mixed-age adult females and moved to test plants. When tested separately in each plant system, median leaf positions of N. californicus from the point of release were greater than those of N. fallacis at 1-8 d. A fan placed in front of a common source unit (1x3m) containing T. urticae and near equal densities of both predaceous mites, provided continuous air (wind) to 3 isolated receiver units located 2.5, 5, and 7.5 m downwind. Receiver units consisted of continuous bean foliage with excess T. urticae, but no predators. Wind speeds at the source and each receiver unit averaged 2.2, 0.9, 0.4, and 0.03 m/s respectively. As predators eliminated prey, N. fallacis dispersed earlier at higher prey densities and further downwind than N. californicus, but cumulative densities of each predator in all receiver units were alike after 20 d. Results of both plant movement studies supported the hypothesis that N. californicus has dispersal traits more like those of a generalist predator of spider mites than does N. fallacis. Spatial patterns of dispersal and biological control of pest mites are discussed in relation to predation types within the Phytoseiidae. / Graduation date: 1997

The seasonal life history of the cereal stem moth (CSM), Ochsenheimeria vacculella Fischer von Roslerstamm, (Lepidoptera : Ochsenheimeriidae) was investigated in a commercial field of annual ryegrass in the Willamette Valley, OR from January 1993 to August 1994. Phenology of life stages, effect of temperature on eclosion, and development of larvae on potential hosts of economic importantce were also studied. First records of parasitization and effects of cultural practices on this potential pest in annual ryegrass were reported. CSM is a recent introduction to North America from a monobasic family of the Palearctic region. Its life cycle is functionally univoltine in commercial ryegrass seed fields. Eggs are characteristically deposited on interior wooden walls, ceilings and straw bales or piles in outbuildings from June through September. Eclosion occurs bimodally with approximately fifty percent of current season eggs hatching in late June and July. The remainder overwinter and hatch in February and March. Larvae ballooned from oviposition sites to potential hosts and were found in annual ryegrass from February to early June. First instar larvae typically mine leaves; later stadia are stem borers. Variance to mean ratios of larvae sampled in annual ryegrass described a clumped population. Pupation occurred from late May to early July. The pupa was enclosed in a flimsy cocoon usually located on the inside of a flag leaf's sheath. Shortly after emergence in early June and July, adults fly to outbuildings preferentially remaining within those where grass straw has been stored. Migration from the field and subsequent flight, copulation and oviposition within buildings occurred only on bright days from approximately noon to 4:30 pm (PDT) through September at which time most adults have died. Two species of larval parasitoids in the Eulophidae and Ichneumonidae were very abundant in the annual ryegrass field under study during June and July 1994. Their combined parasitization rate of CSM larvae exceeded ninety percent. A frequency distribution of head capsule widths indicates CSM larvae probably develop through five instars. However, inter-instar ratios of head capsule widths did not conform to Dyar's hypothesis. Eggs deposited by females collected in the field and allowed to oviposit in the laboratory did not hatch at either room temperature or 6��C. However, cohorts of eggs hatched readily during incubation at either 10�� or 14��C when observed after two and three months exposure. Nine varieties of six commercially important species of grasses and cereals were evaluated for suitability as larval hosts. Annual ryegrass, Lolium multiflorum Lam., consistently supported the greatest population densities in the field and resulted in greatest survival of larvae in laboratory and greenhouse tests. Removal of annual ryegrass foliage in plots during late winter or early spring to simulate the effect of sheep grazing significantly reduced subsequent larval populations relative to plots without vegetation removal. / Graduation date: 1995

Graduation date: 1995

The efficiencies of wet sieving/sucrose centrifugation (WS/SC) recovery of Pratylenchus penetrans (59 %), Paratylenchus sp., (80 %), and Criconemella xenoplax (66 %) were established. Baermann funnels (BF) recovered significantly more P. penetrans (p = 0.01) and significantly less (p = 0.01) C. xenoplax than did WS/SC. While densities of P. penetrans in stored soil remained constant over the three days following field sample collection, Paratylenchus sp. and C. xenoplax densities increased significantly on the second day and decreased to their original level on the third day. During mist chamber extraction, P. penetrans continued to emerge from peppermint root tissue for 38 days, but 90 % of the total was recovered after 10 days. The standard core, consisting of 500 g dry soil plus the roots and rhizomes in that soil, was developed to express endoparasitic and ectoparasitic nematode densities in peppermint field soil, roots, and rhizomes. Enumerating nematode densities within the different plantsoil components of a particular volume of soil more closely describes the total nematode population pressure on the plant growing in that volume of soil. Therefore, endoparasitic nematode population levels were expressed as numbers in standard core soil, roots, rhizomes, or total core (soil, root, and rhizome populations combined). P. penetrans populations in peppermint fields peaked in early May, decreased through the summer, peaked again in August, and decreased through the fall to a low winter level. Peaks in the P. penetrans population followed peppermint root weight peaks by 3 to 6 wks. Paratylenchus sp. populations remained at relatively low levels throughout the year except for a pronounced peak in August, which followed the root weight peak by 3 to 6 wks. The C. xenoplax population also peaked 3 to 6 wks after the August root weight peak but fluctuated markedly throughout the remainder of the year. From 70 to 90 % of the total P. penetrans population was in roots in early May, decreased to 40 to 50 % by late June and 20 to 40 % in August. Up to 20 % of the population was in rhizomes on some dates, but the rhizome percentage was usually less than 10. Fewer P. penetrans were recovered from rhizomes during the harsh winter of 1988-89 than during the mild winter of 1989-90. Analysis of point samples (pretreatment, posttreatment, and harvest samples) and area under nematode population curves (AUNPC) were used to compare nematode populations in oxamyl-treated (1.1 kg a.i./ha) and nontreated plots in two peppermint fields through the two growing seasons. Point sample analyses detected significant decreases in treated soil, root, and total standard core P. benetrans populations compared to nontreated populations in several pretreatment and harvest sample dates and in two rhizome harvest sample dates. No treatment differences were observed in Paratylenchus sp. or C. xenoplax populations using this analysis. AUNPC analysis detected significant decreases in several treated root and rhizome P. penetrans populations compared to nontreated populations and in total core populations in field 1 during one growing season and in field 2 during two growing seasons. Significant decreases in C. xenoplax populations were observed in one field during one growing season. Peppermint hay weight was significantly greater in treated than in nontreated plots in one of three fields in 1988 and in one of three fields during 1989. Oil in ml/kg fresh hay weight was significantly lower in treated than in nontreated plots in one of three fields during 1989. No treatment differences were detected in milliliters of oil distilled from 2m² field area. Peppermint oil production is the final measure of a treatment from a mint grower's perspective. Because oxamyl had no effect on mint oil production, AUNPC appears to be a better measure of parasitic nematode pressure on peppermint, since this method of analysis detected fewer significant differences between nematode populations between treated and non-treated plots. / Graduation date: 1991

Glasshouse and growth-chamber experiments were conducted to evaluate primisulfuron phytotoxicity and the influence of adjuvants on downy brome and Kentucky bluegrass. GR₅₀ (50% growth reduction) values were 0.97 ± 0.57 and 8.07 ± 1.85 g/ha for downy brome and Kentucky bluegrass, respectively. Primisulfuron was applied to downy brome and Kentucky bluegrass at 3 placement sites; foliar, soil, and foliar plus soil. Foliar or foliar plus soil applications were more effective at reducing downy brome dry weights than the soil application of primisulfuron, while Kentucky bluegrass was injured more from the soil or foliar plus soil applications than from the foliar application of primisulfuron. Primisulfuron at 5 g/ha applied alone reduced downy brome dry weights by 5%, whereas, when an adjuvant was added, dry weights were reduced by 52 to 83%. Primisulfuron was more phytotoxic to downy brome at alternating temperatures of 8-16 C and 16-24 C than at 0-8 C. Phytotoxicity of primisulfuron was less when downy brome plants were stressed for soil moisture after herbicide treatments than when the plants were not stressed or only stressed before treatment. / Graduation date: 1999

The effects of fenamiphos on soil and root populations of Pratylenchus penetrans were evaluated in four red raspberry cv. Willamette fields in Northwestern Oregon. Field 1 was a silty clay loam with 53% organic matter (OM). Field 2 and 3 were silty loam soils with 3.25 and 2.55% OM, respectively and field 4 was a silty clay with 7.1% OM. The nematicide, fenamiphos (10 kg a.i./ha) was applied in broadcast or band treatments on November 15, 1989. Additional plots in field 3, received a band-nematicide treatment on December 28, 1989 to evaluate the effect of application date on the control of P. penetrans in red raspberry. Field 4 had plots in sites with and without grass and weed ground cover in the aisles between raspberry rows to examine effects of ground cover on nematicide efficacy. Nematodes from soil and roots were sampled monthly from all plots in each field from October 1989 to October 1990. Soil populations of P. penetrans sampled within rows decreased between the October and December sampling dates in all four fields. Soil populations in 3 fields increased in density during mid-summer and reached their highest peak in the middle of September. A similar pattern occurred in P. penetrans soil populations from plots with or without ground cover in aisles between rows of raspberry in field 4. However, in this field, numbers increased in July and reached their peak density in August. Root populations of P. penetrans from red raspberry reached their highest number during spring and summer at all fields. No significant (P>0.05) differences in effectiveness of fenamiphos were detected between band and broadcast method of application and, also between the 2 application dates. Seasonal mean densities of soil populations from band application was only significantly lower than in nontreated controls in areas with ground cover in field 4, respectively. High variability in the numbers of P. penetrans in soil and roots of raspberry was observed throughout the year. Therefore, conclusions about the effectiveness of fenamiphos were difficult to assess. The efficiency of Baermann funnels was 43.9%, when a known number of P. penetrans was added to soil. Total yields of P. penetrans extracted from raspberry roots by mist chamber root extraction (MCRE) were higher (P = 0.05) than yields extracted by polyethylene plastic bag root incubation (PBRI). Approximately 90% of the total P. penetrans recovered was achieved after three and seven days of extraction for PBRI and MCRE, respectively. However, the extraction efficiency of MCRE was 30% higher than PBRI and the daily recovery lasted 28 and 18 days, respectively. / Graduation date: 1992

No description available.

No description available.

Public tendency, of late, is to reduce liberal use of harmful synthesized chemicals for promoting plant health. Today, biological control is becoming a commonly cited disease control option. Biological control agents (BCAs) not only control disease , but also promote plant growth. Application of biological control is based largely on knowledge of control mechanisms employed by antagonists, as well as the means of application that will ensure that an antagonistic population is established. Knowing the advantages is not the only factor that should be considered before application commences as, the disadvantages must be clearly outlined and explored further before a constructive decision as on implementation of biological control. A literature review was undertaken to provide the necessary technical information about biological control, its potential uses, methods of application, mechanisms of action employed, advantages and disadvantages associated with biological control application, public perceptions and the potential future of biological control. Diseases encountered within the KwaZulu-Natal Midlands on pasture and turf grasses were determined by a once-off survey conducted over 1999/2000. The aim of the survey was to determine broadly the management practices of farmers and groundsmen in KwaZulu-Natal and the potential impact of these on the occurrence of weeds, insects and diseases. The survey also addressed the level of existing knowledge about biological control and willingness to apply such measures. In the pasture survey, farmers were questioned about: soil type, grass species common used, irrigation , fertilization and liming, grazing programs and weed, insect and disease occurrences and control measures implemented. The same aspects were addressed in a survey to a representative sample of groundsmen (turfgrass production) , including also: topdressing, greens base used, drainage systems, mowing practices and decompaction principles. The survey showed correlation between pest incidence and management practices implemented. In terms of pest control, both farmers and groundsmen indicated a stronger preference to the use of herbicides , insecticides and fungicides. Use of fungicides for disease control by farmers is considered an often unfeasible expense, rather more emphasis was placed on implementing cultural control methods. At present farmers do not apply biological control strategies, but they did indicate much interest in the topic. Alternatives to current, or lack of current, disease management strategies are important considerations, with two new diseases identified in the KwaZulu-Natal Midlands just within the period of this thesis. Biological control strategies are implemented by 8% of the groundsmen surveyed, with emphasis being placed on augmenting the already present natural predators rather than the introduction of microbial antagonists. Although often mis-diagnosed by farmers Helminthosporium leaf spot is a common disease in the KwaZulu-Natal Midlands on Pennisetum clandestinum (kikuyu), This disease reduces pasture quality and detracts from the aesthetic appearance and wearability of turfgrasses. Helminthosporium leaf spot is incited by a complex of causal agents , Bipolaris was confirmed as the casual agent of Helminthosporium leaf spot on kikuyu at Cedara. Disease control by two BCAs, Bacillus (B. subtilis Ehrenberg & Cohn.) and Trichoderma (T. harzianum Rifai), as commercial formulations was tested against the fungicide, PUNCH EXTRA®. In vitro, Trichoderma was shown to be aggressive in controlling Bipolaris sp. In vivo, disease control achieved with Trichoderma kd was comparative with PUNCH XTRA® but not statistically different (P>=0.05). Trichoderma and Bacillus provided better disease control in comparison to an untreated control. Improved growth of Lolium sp. was determined in vitro, with Trichoderma kd and Bacillus B69 treatments. The microbe-based treatments accounted for growth stimulation, with significant (P<=O.05) growth differences noted. A microbial activator, MICROBOOST®was added to the treatments to improve microbial efficiency. Improved plant growth with MICROBOOST® applications was shown. Improved growth associated with microbial treatments, Trichoderma harzianum kd; Bacillus subtilis B69 and Gliocladium virens Miller, Gibens, Foster and con Arx. ,was also determined in vivo at Cedara, on L.perenne L., Festuca rubra L. and Agrostis stolonifera L. Establishment of a suppressive soil with antagonistic microbes resulted in significant (P<=O.05) effects on final grass coverage (except G. virens), as well increased root and shoot lengths (P<=O.05). Increased germination rates, as expressed in vitro, were not shown in vivo. Microbial activity with the application of MICROBOOST® showed little effect on germination but increased root and shoot lengths significantly (P<=O.05). Increased weed growth associated with the treatments (except G. virens) was considered a drawback of the microbial-treatments. Microbial treatments were also applied to pasture grasses. An in vitro grazing trial was established at Cedara, using L. multiflorum L. to evaluate the microbe-based treatments Trichoderma kd, Bacillus B69 and G. virens for improved pasture establishment and for increased grazing preference by Dohne Merino sheep. Trichoderma kd was associated with increased dry and wet biomass , but lower dry matter yields in comparison to the control. Only G. virens accounted for a higher dry matter percentage than the control. However, differences between the control and the microbial treatments was very small and not significant (P>=0.05). Of the three grazing observations made, sheep showed no grazing preference to plots with or without microbial treatments In general, the body of this research has shown that microbial treatments have the potential for increased disease control and growth stimulation of grasses. However, lack of significant differences between microbial treatments and controls has raised the question as to effect of external factors on microbial activity and survival, especially in vivo. This raises the question as to the validity of the use of microbial treatments where growth conditions cannot be controlled , remembering that the cost of establishment must be covered by the economic returns from utilization. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

No description available.