Anhydrous ammonia as a control for phymatotrichum root rot and studies on its mode of action.
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| Format: | Thesis Book |
| Language: | English |
| Published: |
1981.
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| Online Access: | Link to OAKTrust Copy Link to ProQuest Copy |
| Abstract: | Phymatotrichum root rot of cotton causes severe reductions in cotton yield each year in the Blackland region of Texas. Deep placement of anhydrous ammonia (NH(,3)) was evaluated as a potential control measure for reducing this disease. NH(,3) was toxic to both the mycelium and sclerotia of Phymatotrichum omnivorum (Shear) Duggar. Mycelium was more sensitive to NH(,3) and a one minute exposure to 4 (mu)g/ml was lethal. Sclerotia were more resistant to NH(,3) fumigation. NH(,3) concentrations below 21 (mu)g/ml were not toxic to sclerotia in vitro even after a 48 hr exposure. At 28 (mu)g/ml NH(,3) toxicity was proportional to exposure period. Exposure of sclerotia to NH(,3) concentrations of 42 (mu)g/ml or greater, for 12 hours, resulted in 100% kill in vitro. Higher concentrations of NH(,3) were required to achieve toxicity to sclerotia in situ, with 138 (mu)g/ml and 276 (mu)g/ml resulting in 65% and 21% germination respectively. NH(,3) was extremely reactive with Houston Black clay and movement was restricted. Maximum horizontal movement was approximately 10 cm from the chisel trace. NH(,3) also moved vertically, with the majority accumulating in the level 7.5 cm above the injection point. There was no downward movement of the gas. Fumigation resulted in an NH(,3) retention pattern 20 cm wide and 22.5 cm high. Greenhouse experiments were conducted in order to evaluate NH(,3) as a control for Phymatotrichum root rot in a controlled environment. Soils not treated with NH(,3) had the highest incidence of disease, 71%. More important than final percent disease was the delayed onset of disease caused by NH(,3) fumigation. Disease first appeared in non-treated soils and did not appear in any of the treated soils until 10 days later. Delay of disease onset in the various treatments was evaluated by determining the coefficient of velocity of plant death (CVPD). |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Plant Pathology." |
| Physical Description: | xi, 105 leaves : illustrations (some color) ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 98-104). |