356 ROBERT A. SCHMIDT 



Snow, G. A., and R. C. Forelich. 1968. Daily and seasonal dispersal of 



basidiospores of Cronartium fusiforme. Phytopathology 58: 1532-1536. 

 Snow, G. A., H. R. Powers, Jr., and A. G. Kais. 1969. Pathogenic 



variability in Cronartium fusiforme, p. 136-139. In Proc. 10th South. 



Conf. Forest Tree Improv. 235 p. 

 Snow, G. A., and R. W. Roncadori. 1965. Oak leaf age and susceptibility 



to Cronartium fusiforme. Plant Dis. Rept . 49: 972-975. 

 Snyder, E. B., P. C. Wakeley, and 0. o. Wells. 1967. Slash pine provenance 



tests. J. Forest. 65: 414-420. 

 van der Plank, J. E. 1968. Disease resistance in plants. Academic 



Press, New York. 206 p. 

 Wells, 0. 0. 1966. Variation in rust resistance among pine seed sources 



and species in a Mississippi planting. Forest Sci. 12: 461-463. 

 Wells, 0. 0., and P. C. Wakeley. 1966. Geographic variation in survival, 



growth and fusiform rust infection of planted loblolly pine. Forest 



Sci. Mongr. 11 . 40 p. 



FLOOR DISCUSSION 



(Also discussed here are three previous papers in this panel section 

 by Snow and Kais, Dinus , and Dwinell covering C. fusiforme inoculation 

 problems and techniques.) 



WEISSENBERG: For my personal interest, I'd like to hear commentary 

 on the influence of age of telial columns on basidiospore density. 



DWINELL: The work of Powers and Roncadori indicated that there was 

 a direct relationship between telial age and sporidial cast. This was 

 the reason we used 2-week-old telia; at that age they produce the maximum 

 sporidial cast. 



GERH0LD: I have gathered from some of the comments that density of 

 basidiospores in the nursery bed type of inoculation is rather variable, 

 that is, that the number of spores per seedling might vary even across 

 small areas. Would it be possible to adapt some of the more sophisticated 

 inoculation chambers, like the one developed by Dwinell, for use in the 

 nursery. I'm thinking of a mobile unit that travels down the nursery bed, 

 perhaps with some sort of spore distribution system using a manifold. 



DWINELL: I really don't know if we need such close control for mass 

 or screening inoculations in the nursery. Instead I think we need basic 

 information on the relation of inoculum density to infection. By knowing 

 spore density in the screening test, and what that density means in 

 respect to infection, we might be able to get along very well. However, 

 we're not at the point yet where we are involved in a mass screening 

 program. We will have to consider these problems once we reach that point, 



KINLOCH: Dr. Schmidt, what is the range or limitation of temperature 

 control in your screening shed? Is this a limiting factor? 



SCHMIDT: In our studies in Florida temperature control has not been 

 too much of a problem. We control relative humidity by spraying water on 

 the canvas sides of a large screening shed. Coincidentally we get evapora- 

 tive cooling, and this maintains the temperature around the 70°F optimum 

 even when outside temperature is 80° F and above. Thus temperature control 

 hasn't been a problem with the screening shed. 



