INOCULATION" OF EASTERN WHITE PINE WITH BLISTER RUST 375 



The techniques of artificial inoculation do permit us to exert some 

 measure of control over the course of the pathological sequence. So far 

 only a few basic methods have been employed, and my concern here is 

 largely with inoculation of pines, but with some reference to production 

 and maintenance of inoculum on ribes . Besides the procedures themselves, 

 factors influencing the success of inoculation are also considered. Many 

 of these are factors affecting the infection process and are emphasized 

 here, since the purpose of inoculation is to lead to infection, or a 

 resistance reaction to it. Such factors as environmental influences and 

 age and type of stock may be extremely important in determining efficiency 

 and reliability of a screening test, and thus may become an absolute part 

 of a technique. 



INOCULATION METHODS 



NETHOD VS. TECHNIQUE 



A method may succeed or fail according to the technique followed in 

 accomplishing it. Technique connotes expertise or manner of performance, 

 whereas a method is considered as an orderly or set form of procedure. 

 The two terms are differentiated here not to be pedantic, but to emphasize 

 the fact that reliability of a screening test may be quite dependent upon 

 some of the details followed in effecting an inoculation, and upon an 

 awareness of the differences in results that might be attained by a given 

 method under different conditions. It is appropriate that this panel is 

 concerned with techniques, for the factors influencing results of an 

 inoculation procedure can be quite as important as the procedure itself. 



INOCULATION PROCEDURES 



Spore Casts from Telia-bearing Ribes Leaves 



One commonly used method for inoculating pines is to support telia- 

 bearing ribes leaves over the test plants by means of paper clips, tooth- 

 picks, wire or large-mesh wire screening, and enclose the test beds in 

 cloth cages or tents. The cloth or burlap covering is sprayed with water 

 to provide a relative humidity of about 95 to 100%, or a film of free 

 water on the needles, and to help hold temperature within the range 

 favorable for spore germination and pine infection for periods up to 

 about 72 hours. Shade is sometimes provided to help maintain proper 

 temperature and moisture conditions. This basic procedure was used 

 successfully in the Blister Rust Nursery in Wisconsin, and in most years 

 infection of susceptible control seedlings reached over 90% and up to 

 100% after such inoculations (Riker et al. , 1943; Patton and Riker, 1966). 



Details of providing inoculum and enclosing the test beds have been 

 modified from time to time but essentially the same basic procedure has 

 been followed. Heimburger (1956) planted the petioles of telia-bearing 

 ribes leaves densely in the soil among the small seedlings to be inocu- 

 lated, and later placed entire shoots bearing ribes leaves into the soil 

 close to white pine seedlings and grafts. The advantage here was that 

 ribes leaves stayed fresh longer if not detached from the stem; often, 

 too, shoots rooted and provided inoculum for additional inoculation the 

 next year. 



