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Submitted to: Cotton Farming
Publication Type: Popular Publication Publication Acceptance Date: 3/3/2002 Publication Date: 3/28/2002 Citation: HOWELL, C.R. PRE-EMERGENCE DAMPING OFF IN COTTON SEEDLINGS: CURRENT THINKING ABOUT CAUSES AND CONTROL. COTTON FARMING. MARCH 2002. P. 20. Interpretive Summary: Technical Abstract: The fungus, Rhizopus oryzae, a close relative of the common bread mold, can cause devastating seedling disease in cotton even under planting and soil conditions considered to be very good. The seed treatment fungicides that are normally used to control losses by Pythium species have no effect on R. oryzae. Only fungicides that are used to control losses caused by Rhizoctonia solani are effective against this fungus. It is possible that many symptoms in cotton attributed to R. solani, are actually caused by R. oryzae. During seed germination, susceptible cotton cultivars produce, and release into the environment, chemicals that stimulate germination of the resting structures of the pathogens in soil near the seed. Once this occurs, the seed or seedling is quickly invaded and killed. Scientists are trying to isolate and identify these germination stimulants so that they may be used to fool the pathogens into germinating and wasting their energy ybefore the cotton crop is even planted. Although controlling fungal pathogens of cotton requires combinations of fungicides, the same effect may be achieved with a single biocontrol agent. Seed treatment with a granular preparation of the biocontrol fungus Trichoderma virens controls both P. ultimum and R. oryzae because it interferes with the production and release by the seed of the chemicals that stimulate pathogen resting structure germination. The tendencies of certain cultivars to release pathogen germination stimulants into the soil during germination should be taken into account when breeding for new cultivars. |
