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Wis^ The Relation of Leafhoppers and Aphids to the Transmission 

 of Vegetable Crop Viruses . Learn species responsible for 

 dissemination of truck crop viruses and their importance in 

 epidemiology of diseases under field conditions. Habits, host 

 relations, migration, and reducing insect vectors by insecticidal, 

 biological, and cultural means will be studied. Laboratory and 

 greenhouse studies will show basic factors involved in vector-virus- 

 plant relationships; as acquisition sequence; inoculation, retention, 

 and latent periods, and vector feeding habits. 

 Ent. 725 



Soil-Borne Diseases 



Ala. The Relationship of Soil Microflora to the Incidence of 



Disease in Plants . Learn relationships between activities of 

 general soil microflora and pathogenicity of soil-borne plant 

 parasitic microorganisms. Develop biological methods of control- 

 ling soil-borne diseases of Alabama crop plants. 

 Bot. & PI. Path. 560 (S-26) 



Calif. Influence of Crop Residues on Cortical Fusarium Root Rots, 



and Streptomyces Diseases . Assemble data on role of specific crop 

 residues in cortical Fusarium root rots, from field, greenhouse, and 

 laboratory research, and learn: (l) influence of specific crop 

 residues on each of several cortical Fusarium root rots; (2) if 

 influence of a specific crop residue is same for each rot; (3) 

 if causes for effects are biological. 

 PI. Path. 1657 (W-38) Coop. ARS 



Conn. Pathogenesis by Soil Borne Organisms . To (1) learn pathogenic- 

 ity and distribution of strains of Verticil] ium attacking potatoes; 

 (2) make comparative study of enzymes and other toxic metabolites 

 produced by soft rotting and vascular wilt organisms; (3) relate 

 these products to damage caused to host plants and to resistance 

 to attack of related varieties; (4) use data in developing control 

 measures against soft rotting and vascular wilt diseases. 

 PI. Path. & Bot. 639 



Ga. The Microbiology of Crop Residues as Influenced by Nitrogen 



Additions and Other Management Practices . (1) Relate certain 

 management practices to soil organic matter and resulting effect 

 of soil organic matter on nutrient availability, aggregation and 

 moisture availability; (2) learn effect of nature and C :N ratio 

 of organic residues on persistence of materials in soils and effect 

 of materials on soil properties. 

 Agron. 314 (S-35) Coop. ARS 



