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Management of cotton seedling disease complexes
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The objective of this research was to evaluate combinations of approaches for the management of seedling diseases of cotton caused by soilborne pathogens, including the use of host resistance. Over 200 cotton lines were screened for resistance to Rhizoctonia solani with infested soil in growth chamber experiments and in infested fields. From these trials, 20 lines were identified with resistance to R. solani. Nine lines were selected for resistance screening to Pythium ultimum and R. solani in a field experiment where soil was naturally infested with P. ultimum and artificially with R. solani. The variety 'Paymaster 2326BG/RR', with a seed treatment of captan only, was included as a positive control for Pythium and R. solani infection and with a metalaxyl plus triademenol seed treatment to provide Pythium and R. solani protection. At 28 days after planting, 8 of the 9 breeding lines had significantly higher stands (P=0.05) than the captan-treated check. The captan-treated 'Paymaster 2326BG/RR' had significantly lower yield (P=0.05) than the metalaxyl plus triademenol treated variety and 8 of the breeding lines. Another experiment was conducted testing combinations of seedling disease management tools for control of seedling disease complexes in naturally infested fields. Treatments for each field included all available management tools: fungicide seed treatments; an in-furrow fungicide at planting; multiple varieties; and a nematicide. 'Paymaster 2326RR' with no seed applied fungicides was included as a control. Seed treated with a fungicide active against Thielaviopsis basicola and R. solani, although slower to emerge, had significantly higher (P=0.0001) root health, as determined by hypocotyl ratings and root necrosis ratings, than seed treated with a fungicide active against only R. solani in several fields. The experimental genotype 94T#49 1524-1 had a significantly poorer stand (P=0.0001) than 'Paymaster 2326RR' and 'Paymaster 2200RR'; however, the seed was of a lower quality than other entries included in the experiment. The overall yields from all four sites in 2000 showed a significantly higher yield (P=0.0004) with the addition of aldicarb. 'Paymaster 2326RR' had the greatest response to aldicarb. Combining management tools based on specific disease situations can be an effective approach for seedling disease control.
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Includes bibliographical references (leaves 45-50).
Issued also on microfiche from Lange Micrographics.
Fichtner, Scott Michael (2001). Management of cotton seedling disease complexes. Master's thesis, Texas A&M University. Available electronically from
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