Rhizoctonia solani (AG-3), the causal agent of Rhizoctonia disease of potato, overwinters as sclerotia on potato tubers. To develop a biocontrol strategy based on the prevention of the sclerotial germination, an isolation of microorganisms colonizing sclerotia of infected potato tubers (cultivars Norland, Atlantic and Souris), was conducted. In vitro screening was used to select effective antagonistic fungi against Rhizoctonia solani. Fifty fungal isolates were selected in order to cover all identified genera and potato variety and examined for their ability to inhibit germination of sclerotia which were incubated with the test fungus for 14 days. Twenty-four (24) fungal isolates were retained based on their ability to reduce sclerotial viability by more than 50% as compared with 100% viability of untreated sclerotia. These 24 isolates were further examined for their ability to protect Table beet seedlings against the pathogen in greenhouse soils. Based on their ability to protect Table beet seedlings from Rhizoctonia infections and to increase the number of secondary roots and root length isolates, F2, F11, F132, F158, and F258 were screened and test their efficacy to increase beet seed germination in field soils. (Abstract shortened by UMI.)

A project was developed to determine the feasibility of using liquid hog manure as a nutrient source (Nitrogen) for the potato crop. A survey of liquid hog manure storage facilities on Prince Edward Island (P.E.I.) provided a sampling technique and the range of nutrients found on hog farms. It was concluded from the data that there were large differences between farms and on farm manure sampling was required to determine accurate nutrient applications. An infrastructure was designed, constructed and tested for storage, handling and the application of liquid hog manure at the Harrington Research Farm, Crops and Livestock Research Centre, Charlottetown, P.E.I. Data from the first of two three year experiments determined that the placement of liquid hog manure under the sown potato row and beside the row (0.23 m) provided yields better than manure placed between the sown rows. These yields were not different for the extra Nitrogen fertilizer treatment. The second field experiment examined the placement of liquid hog manure by various injector designs between the rows after the potato crop was planted. Potato tuber yield data over the three years indicated no differences among injector design nor between the injector treatments and the treatment which received the extra Nitrogen fertilizer. Over both experiments there was a decline in the severity of Rhizoctonia ( Rhizoctonia solani) in one year for plots receiving manure compared to those which received only inorganic fertilizer. There were no differences in the incidence or severity of scab (Streptomyces scabies) over the study. In general liquid manure can be used as nutrient source for the potato crop on P.E.I.

Much research has proven that computer controlled vegetable storage can achieve better storage conditions than traditional control systems. During the last 10 years, the use of microcomputer-based environmental control systems has become commonplace. However, to take full advantage of this computerization of the control process, it is not enough only to program the control functions that are performed by normal analog equipment. New and better control strategies must be developed. Recent advances in computer technology have made possible the development of expert systems; a branch of artificial intelligence. One of the advantages of developing such a system is that it provides a reasoning tool which approaches the level of proficiency human experts exhibit in that field. The application of new control methods using expert systems has been extensively demonstrated for greenhouse environments. However, the application of expert systems for the control of vegetable storage is still to be investigated. In the first phase of this project, the development and implementation of a sophisticated control software, using a conventional algorithm-based programming language, were achieved. Throughout the three years of experimentation in an industrial potato storage, the software proved to be appropriate for the control of storage environmental parameters (temperature and relative humidity). During the second phase, the application of an expert system for the on-line control of potato storage was explored. The development of a rule-based expert system, that could replace the conventional algorithm-based control routines was achieved. The integration of the expert system into the control software will result in a highly efficient control software, which can easily be maintained and improved as new knowledge emerges. The use of an expert system will also render possible the representation of heuristic knowledge in the form of rules, which was not possible with the use of conven

Magistro darbe tiriama trąšų įtaka vidutinio ankstyvumo bulvių ‘Laura’ kokybei ir derliui. Darbo objektas – bulvės, užaugintos chemizuotame ir ekologiniame fonuose, Šiaulių apskrityje, Radviliškio rajone, Raudondvario gyvenvietėje.. Darbo tikslas – palyginti mėšlo, komposto, biohumuso, ekologiškų trąšų „Activit“ ir mineralinių sintetinių trąšų „YARA MILA“ įtaką vidutinio ankstyvumo bulvėms ‘Laura’. Darbo metodai – LŽŪU Aplinkotyros laboratorijoje nustatyti elektrocheminiai (rūgštingumas – šarmingumas (pH), absoliutusis redokso potencialas (rH) ir savitasis elektrinis laidis(γ)) bei cheminiai (C vitamino kiekis) rodikliai. Skaičiuojami bulvių gumbai, stiebų aukštis ir skaičius, bulvių derlius. Visos įterptos trąšos prilygintos prie vienodo azoto kiekio (30 kg/ha). Tyrimų duomenys apdoroti matematiniais – statistiniais metodais. Duomenų grupavimui ir statistinei jų analizei atlikti buvo naudota kompiuterinė Microsoft Excel programa. Darbo rezultatai. Atlikus tyrimus įvertinta trąšų įtaka vidutinio ankstyvumo bulvėms ‘Laura’ ir gauti tokie rezultatai: bulvių derlius, gumbų skaičius, stiebų aukštis, stiebų skaičius didžiausias buvo tręšiant bulves sintetinėmis mineralinėmis trąšomis „YARA MILA“. Lyginant tik ekologiškas trąšas, didžiausias derlius, gumbų skaičius, stiebų skaičius buvo tręšiant ekologiškomis trąšomis „Activit“, mažiausias derlius gautas tręšiant mėšlo kompostu. Žemiausi stiebai gauti tręšiant biohumusu, stiebų skaičius patikimai mažesnis buvo kompostu tręštų... [toliau žr. visą tekstą] / Master's thesis investigated the influence of fertilizer medium early potatoes 'Laura' quality and yields. The object of work - potatoes grown in chemical and organic fertilization, in Radviliškis district, Raudondvaris village. The objective of work - the manure, compost, biohumus, organic fertilizer "Activity " and synthetic mineral fertilizers “YARA MILA" on medium early potatoes 'Laura'. Method of work - in LŽŪU Environmental Laboratory was observed electrochemical (acidity -alkalinity (pH), the absolute redox potential (rH) and electrical conductivity (γ)) and chemical (C vitamin content) characteristics. Calculating the potato tuber, stem heigh and number, and potato yield. All fertilizers equate at equal quantity of nitrogen (30 kg / ha). Research data processing mathematics - statistical methods. Data grouping and the statistical analysis was used in Microsoft Excel computer program. Results of work – investigations to assess the influence of fertilizer medium early potato ‘Laura’ and the following results: potato yield, tuber number, stalk height, stalk number was the largest potatoes fertilized with the mineral synthetic fertilizers “YARA MILA”. Compared the organic fertilizer only, the maximum yield, tuber number, stem density was fertilized with organic fertilizer “Activit”, the lowest yield was obtained due to the application of manure compost. The lowest stem was fertilized with biohumus, stem density significantly lower in compost fertilized potato... [to full text]

The production of Jersey Royal potatoes is an important industry for the island of Jersey. The crop is grown annually, and sometimes biannually, so there is no opportunity to practise crop rotation in order to control potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis. Control of these pests in Jersey has traditionally relied on the use of nematicides, but with increased public pressure to reduce the use of pesticides and the intention of the Government of Jersey to eventually ban them, there is a desire for an alternative methods of control to be developed. Three nematophagous fungi, Plectosphaerella cucumerina, Paecilomyces lilacinus and Verticillium chZamydosporium, were isolated from PCN cysts taken from potato fields in Jersey. The efficacy of these fungi for the control of PCN was studied to determine their suitability for use in an integrated pest management programme. The radial growth rates of the nematophagolls fungi were reduced when grown on media amended with the fungicides Gambit and Rizolex, commonly used for the control of Rhizoctonia solani, another major pathogen of potatoes. Radial growth of V. chlamydosporium was also inhibited by Monceren and the nematicide Vydate. Growth of R. solani was inhibited by P. lilacinus at 20°C and 10°C in vitro and by V. chlamydosporium at 20°C, but the strain of V. chlamydosporiurn used did not grow at 10°c. Plectosphaerella cucumerina was a poor saprophytic competitor when grown against R. solani, P. lilacinus and V. chlamydosporium, therefore it may not be a suitable soil applied agent as it is out grown by other fungi in the soil. Paecilomyces lilacinus in a pelleted support matrix made from an alginate, gave better control of R. solani than non-formulated P. lilacinus alone. Of the different formulations of nematophagous fungi tested in pots, P. lilacinus incorporated into alginate pellets reduced the numbers of peN by the most (79.5%) and when applied in a field trial, reduced PCN population increase by approximately 60%. Plectosphaerella cucumerina, when incorporated into alginate pellets, also reduced field population increase by approximately 60%. A combination of these two formulated fungi tested in a plunge trial gave a poorer level of control than the fungi added individually. The fungi remained viable in alginate pellets for at least 18 months. The population composition of PCN in Jersey was previously unknown. Using an ELISA technique, this study has shown both PCN species are present, but the proportions were not determined. To ascertain whether the early lifting of Jersey potatoes was selectively reducing levels of one of the species of PCN, DNA was extracted from nematodes stained in situ in the roots of potatoes. The results were inconclusive and further work is required.

Field experiments were conducted during the 1989 dry season (July to December) at the Manggoapi Farm of the Faculty of Agriculture, Cenderawasih University in Manokwari, Irian Jaya, Indonesia. The objectives of the experiments were to determine the effects of four sweet potato cropping systems on the population density of sweet potato weevils (SPW) and on the diversity of other insects within these agroecosystems. / Fewer SPW were found in intercropped sweet potato + corn (2 weevils per kg infected tubers), sweet potato + soybean (21 weevils), sweet potato + corn + soybean (8 weevils) than in monoculture sweet potato (37 weevils); percentage of damaged tubers followed the same trend, ranging from 2.6% to 14.0% in intercropped sweet potato, to 21.9% in the sweet potato monoculture. However, the higher number of SPW and damaged tubers in the monoculture did not reduce yield below that in the intercropped plots. / Insect and spider populations were more diverse in the intercropped sweet potato systems than in monoculture. Number of arthropods increased throughout the growing season. Intercropping may reduce the population density of other insect pests associated with sweet potato and may increase the population density of natural enemies.

A 4.87 hectare potato field at St. Leonard d'Aston, Quebec was instrumented to measure surface runoff and tile drain flow over the 2 year growing season period, 1989-1990. The soil type was a Ste. Jude sandy loam. Several soil and water parameters and NPK concentrations in runoff were measured. The CREAMS (Chemicals, Runoff and Erosion from Agricultural Management Systems) computer simulation model was validated for the study site. / Observed N concentrations in tile drain flow exceeded the Canadian water quality guideline of 10 mg/L. Observed P concentrations were less than 0.01 mg/L; and K concentrations, for the most part, exceeded 10 mg/L. / CREAMS overpredicted event surface runoff depths, and underpredicted event percolation depths. However, total monthly surface runoff and percolation depths closely matched observed values. / CREAMS overpredicted event nitrate concentrations in tile drain flow. There was a poor match between predicted and observed event nitrate concentrations in tile drain flow (coefficient of predictability, CP$ sb{ rm A}$ = 104.95). However, predicted total monthly nitrate load closely matched observed values (CP$ sb{ rm A}$ = 0.84). Total monthly and seasonal nitrate loads in tile drain flow were underpredicted.

No description available.

Graduation date: 1971

Potato leafroll virus (PLRV) causes yield and quality losses in potato. PLRV is identified by plant symptoms and serological tests such as an enzyme-linked immunosorbent assay (ELISA). A similar serological test, direct tissue blotting assay (DTBA), was used to detect and monitor PLRV movement in field-inoculated Russet Burbank plants and plant tissues from Russet Burbank and Russet Norkotah seed tubers submitted by growers for winter certification tests. DTBA was as accurate as ELISA and easier to use for detecting tuber-perpetuated PLRV in stems and petioles of plants grown from grower-submitted seed tubers. ELISA detected twice as many PLRV positives as DTBA in leaflet tests. DTBA detected PLRV in tuber tissue but results matched ELISA in only 74% or less of the samples. Results of DTBA tuber tests were sometimes difficult to interpret while stem and petiole results were distinct and unambiguous. As inoculations were delayed later in the season and as plants matured, PLRV infection levels decreased sharply, most often within a two week period in early July. In same-age plants inoculated 43 days after planting but 18 days apart, early inoculation produced higher PLRV levels. Conversely, when same-age plants were inoculated 62 days after planting but 19 days apart, late inoculation produced higher PLRV levels. This discrepancy is not fully understood, but larger tuber size at the later inoculation probably produced a stronger sink for source-to-sink translocation of nutrients and phloem-limited viruses. Results of DTBA winter grow-out tests of summer-infected tubers approximated those of ELISA and visual inspections. Indirect DTBA testing of tubers utilizing stem and petiole tissues from winter growout plants detected more PLRV than directly testing tuber tissue 21 days post inoculation in summer. DTBA detected current season (primary) PLRV less reliably than secondary (tuber-borne) PLRV, similar to reported ELISA results. PLRV infection increased tuber numbers but decreased size. Size reduction was most evident in plants infected early in the season. Average tuber size in healthy plots was always larger than the average tuber size in infected plots. Within an infected plant, small tubers tended to be infected less often than large tubers. / Graduation date: 1993