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Studies on the parasitism of Aphelenchus avenae Bastian, 1865.Terry, E. R. January 1966 (has links)
Corn is one of the three most valuable cereals in the world, and at present its adoption as a grain crop in Quebec is being encouraged. [...]
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Host-parasite relationships in Verticillium wilt of tobacco.Wright, Donald Stranack Cottle. January 1972 (has links)
No description available.
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Etude sur les ravageurs du chou et en particulier sur la mouche du chou, Hylemya brassicae Wiedemann (Diptera:Anthomyiidae).Vincent, Charles, 1953- January 1980 (has links)
No description available.
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Production of Conidia, selection of inoculum density, and timing the first fungicide application to manage Septoria blight of celeryMudita, I. Wayan January 1992 (has links)
Septoria blight of celery (Apium graveolens var. dulce), induced by Septoria apiicola Speg., is a destructive disease that requires fungicide applications for its management. A reliable method of inoculum production was established. Best sporulation was obtained on celery agar (CA) at a predicted optimum temperature of 22.4$ sp circ$C. A moderate inoculum density within a range of 17-35 conidia/cm$ sp2$ of leaf surface provided non-coalescing lesions necessary for rapid enumeration. Initial blight incidence thresholds of about 0.6 and 0.5% to time the first fungicide application were established based on the proportion of maximum plant weight equivalent to the cost of one fungicide application calculated plant weight and petiole number per plant, respectively, in the summers of 1990 and 1991. The IBI levels of 0 and 2% to time the first fungicide application provided non-significant results in terms of the final amount of blight and yield. (Abstract shortened by UMI.)
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Production and diseases of Jerusalem artichokeLaberge, Christiane. January 1986 (has links)
No description available.
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Biologie et répression des larves des racines, Hylemya spp., inrestant les cultures de crucifères.Ritchot, Claude. January 1968 (has links)
No description available.
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Development of economic thresholds for semiloopers (Lepidoptera: noctuidae) on four soybean cultivars in ZimbabweLapointe, Renée January 1992 (has links)
Soybean leaf consumption for the most common semilooper species, Trichoplusia orichalcea (F.) was established in the laboratory using a leaf area meter. The total consumption per larva was 120,85 cm$ sp2$. The yield reduction of our soybean cultivars (Glycine max (L.) Merrill) being Duiker, Gazelle, Roan and SCS1 was measured in relation to different levels of defoliation. The defoliation was induced manually singly or sequentially over three different growth stages. / At soybean maturity, counts of pods per plant, number of seeds per plant, weight per 100 seeds and weight of seeds per plant were obtained. Yields were converted to a percentage of yield and linear regressions fitted to the relationship between percentage yield and defoliation. The percentage yield was influenced by the cultivars, the levels of defoliation, and the timing of defoliation. / The most critical growth stage for defoliation was the seed development stage, but the differences between them were small and not significant. SCS1 was the most resistant cultivar to defoliation, while Duiker was the most susceptible to single defoliation. / The economic thresholds were determined for the soybean cultivars demonstrating significant linear relations between percentage yield and single defoliation. Based on three insecticides and two application methods, the economic thresholds were determined at the flowering stage for Duiker, at the pod development stage for Duiker and Roan and at the seed development stage for Duiker, Gazelle, Roan, and SCS1 cultivars. The numbers of semilooper caterpillars per metre of row required to reach the economic thresholds, are generally higher than the natural levels of infestation.
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Mechanisms of pathogenesis in Sclerotium bataticola on sunflowers.Chan, James Yu-Ho. January 1968 (has links)
No description available.
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Morphology, membrane characterization and detection of a bacterium associated with ratoon stunting disease of sugarcane.Pillay, Dorsamy. 22 October 2013 (has links)
Ratoon stunting disease (RSD) of sugarcane was first recognized in 1944
in Queensland, Australia (Steindl, 1961). The disease occurs worldwide
and causes significant yield losses, especially during drought. RSD
produces no external symptoms except a non-specific stunting (Steindl,
1961). RSD, which was first recorded 1n South Africa in 1953 (Anon., 1960),
causes a greater overall loss in yield than any other sugarcane disease
in South Africa. Yields of sugarcane are reduced by 20% to 40% and the
harvest of affected fields declines progressively with successive ratoons (Anon., 1980b). A virus was originally thought to cause RSD, but in 1973, a coryneform bacterium was implicated as the causal agent (Gillaspie et al., 1973; Teakle et al., 1973). In 1980, our laboratory reported the successful
isolation and culture of a coryneform bacterium associated with RSD of
sugarcane and was indicated to be the causal agent (Nayiager et al.,
1980). The lack of a rapid diagnostic technique applicable to mass screening of sugarcane has hindered progress in the control of the disease. There are two types of commonly used diagnostic tests. One test depends on the evaluation of internal stalk symptoms which may require from two to twenty six weeks to develop (Gillaspie et al., 1966; Matsuoka, 1971; Schexnayder, 1960; Singh, 1969). However, these symptoms are not
always present in RSD affected plants and similar symptoms can sometimes
result from other causes (Steindl, 1961). The other test involves
establishing the presence of the coryneform bacterium associated with
diseased plants. The bacterium is visible under high magnification by
phase-contrast microscopy (Gillaspie et al., 1973) or by electron microscopy
(Teakle et al., 1973). Although identification by the latter methods requires little time, the technology involved severely limits the number of samples that can be examined. Recently, serological techniques have been used (Brlansky et al., 1982; Damann et al., 1977; Davis et al., 1980; Gillaspie, 1978b; Gillaspie et al., 1979; Harris and Gillaspie, 1978) but their success has been limited. Besides problems with diagnosis of the disease, the precise morphology and taxonomy of the causal organism is unclarified.
The objectives of this research programme were, firstly, to characterize
the cultured intact bacterium and its constituent membranes both ultrastructurally and immunologically, and secondly, to evaluate various
immunological methods for detection of the bacterium. This study should
contribute to enhancing the taxonomic status of the bacterium and to the
use of a rapid diagnostic technique applicable to mass screening of
sugarcane. Such a technique should eventually contribute to effective
control of RSD. / Thesis (M.Sc.)-University of Durban-Westville, 1984.
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Differentiation of garlic virusesLiu, X. Q. (Xingquan) January 1985 (has links)
No description available.
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