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Studies on variation in Puccinia helianthi.Hennessy, Christopher Martin Reeves. January 1972 (has links)
No description available.
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Genetics of host : parasite relationships between sunflowers and sunflower rust.Miah, Muhammad Abdul Jabbar. January 1967 (has links)
No description available.
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Biology and epidemiology of Plasmopara halstedii on sunflower.Goossen, Philippus G. January 1965 (has links)
The fungus responsible for the downy mildew disease, common on commercially grown sunflowers, is Plasmopara halstedii (Farlow) Berl. et de Toni, one of the Peronosporaceae in the Oomycetes, known to be soil borne and to infect via the roots. [...]
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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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Biology and epidemiology of Plasmopara halstedii on sunflower.Goossen, Philippus G. January 1965 (has links)
No description available.
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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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Studies on relative fitness of two races of Puccinia helianthi, in mixture, on sunflowerPrud'homme, Anne-Marie January 1987 (has links)
No description available.
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The status of the American bollworm, Heliothis armigera (Hubner) (Lepidoptera : Noctuidae), on sunflower in the central TransvaalVon Maltitz, Emil Friedrich January 1992 (has links)
Sunflower production in South Africa has increased four fold since the 1970's. This study was done to elucidate the pest status of Heliothis armigera (Hiibner) on sunflower. Field studies were undertaken at Warmbaths, Brits and Delmas during the summer seasons of 1988/89 to 1990/91. The infestations at the latter two areas were negligible throughout the study period and their statistics have not been included in this thesis. Plant development and oviposition by natural H. armigera populations were found to be correlated as, regardless of planting date, oviposition started at six to seven weeks after planting; when the flowering stage began. A peak in egg numbers was reached by the tenth week with an average for the three seasons at two eggs per plant. The eggs were laid singly on the bracts and bases of the flower buds. A peak in larval numbers was reached at the thirteenth week after planting with the average for the three seasons of 0,4 larvae per plant. The preferred feeding sites were on, between and under the bracts from where the larvae burrow into the pithy tissue of the receptacle. Only six percent of the larvae were found feeding directly on the achenes. Eggs and larvae collected were reared to determine the degree of parasitism. Overall, 19% of the eggs were parasitised; 18% by Telenomus ullyetti Nixon (Scelionidae) and one percent by Trichogrammatoidea lutea (Trichogrammatidae). Larval parasitism at Warmbaths was 23% in 1988/89, 27% in 1989/90 and 34% in 1990/91. Of the parasitised larvae, 44% succumbed to Palexorista prob. laxa (Tachinidae). The remainder were unidentified Braconidae and Ichneumonidae. Predators, such as chrysopids, were observed during the study but their effect on egg and larvae numbers was not studied in detail. A polyhedral virus occurred late in the seasons and caused mortality of the larvae. The low numbers of H. armigera on sunflower, the slight damage to the crop and the reasonably high rate of parasitism, all seem to indicate that H. armigera is not an economica1ly important pest of sunflower and that additional control methods are not justified.
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Studies on relative fitness of two races of Puccinia helianthi, in mixture, on sunflowerPrud'homme, Anne-Marie January 1987 (has links)
No description available.
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The influence of lesion nematode infection on plant water relations and root integrity.Kaplan, David Todd 01 January 1975 (has links) (PDF)
No description available.
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