20 



Ohio Effect of Crop Rotations in the Licidence of Dlaeaaea 



Caused by Soil-Bome Pathogens and Associated Changes in 

 Soil Fxmgus Populations. To determine (l) effect of rotation 

 on incidence of disease caused by soil-borne pathogens from 

 relative amounts of damping-off and root rots of assay plants; 



(2) effect of rotations on numbers and types of soil fungi, 

 and to correlate those changes with disease incidence; and 



(3) host range of soil pathogens on field crops important 



in Ohio, and study antibiotic and antagonistic relationships, 

 soil types, fertilizers, and organic matter vrtiich may affect 

 their pathogenicity. 



Plant Path., Bot. 63-1 



Oreg. Relation of Crop Residues to the Development of Certain 



Root Rot Diseases of Nurseirr Crops . To learn (l) effect of certain 

 crop residues on development of root diseases of ornamental plants, 

 caused by Phvtophthora cinnamoni and P. lateralis ; (2) influence 

 of soil temperature and moisture on effects of cr^p residues in 

 suppressing or stimulating disease development; and (3) if sup- 

 pression of disease associated with certain crop residues is 

 biological, chemical or phvsical. 

 Plant Path. 196 (W-38) 



S.C. A Study of Microbial Antagonisms in South Carolina Soils 

 With Special Reference to Antagonistic Action of Soil Bacteria . 

 Actinottvcetes. and Fungi on Certain Soil-Inhabiting Phvtopathogens. 

 (1) Learn antagonistic action of some microorganisms isolated froa 

 Sputh Carolina soils upon selected phytopathogens ; (2) develop 

 means of utilizing antagonistic reactions as means of biological 

 control of some soil-borne plant diseases; (3) survey soil samples 

 frcHD various sources. Include the rhizosphere of diseased & 

 healthy plants, if possible, & learn the nimber of bacteria, actinomy- 

 cetes, and fungi antagonistic to Sclerotium rolfsii. Rhizoctonia 

 solani . Fusarium spp., Pseudomonas solanacearum . and Pseud omonas 

 tabacum. Study relation of soil pH to presence of antagonistic 

 organisms; and (4) test specific antagonists under greenhouse con- 

 ditions for their ability to prevent parasitism of the phytopathogens 

 on their host plants in sterile soil. 

 Bot., Bact. 133 (S-26) 



Tenn. Associations of Soil Micfoo7» g^n j.sms as Related to Plant Diseases . 

 To (1) determine associations of saprophytic soil microorganisms 

 with pathogenic soil microorganisms which enhance ability to produce 

 epidemics; (2) use antagonistic soil organisms for reducing diseases; 

 and (3) devise crop successions that will thru soil microbiological 

 action reduce ability of semiparasitic organisms to incite disease. 

 Plant Path. 139 (S-26) 



For more information on research in this category, see 

 Part 17, Plant Pathology and Bacteriology. 



