322 ALLAN KLINGSTROM 



KREBILL: Have you tried this without puncture wounds and at various 

 stages of development in the new current year shoot? 



KLINGSTROM: Yes, and I have only had success if I wound the shoots, 

 but on the other hand, the wound can be any type of wound. You can just 

 break the shoot off and apply the spore drops to the broken shoot, or 

 you may just make one little puncture. 



KREBILL: Using Peridermium harknessii , which is a pine to pine rust, 

 workers in the U.S. and Canada have had excellent results without 

 wounding, but only if they time the inoculation very closely. There is 

 probably about a 2 to 4 week period in which infection will occur. This 

 is somewhere near the time of the emergence of the needles from the sheaths. 

 Consequently, unless you are aware of what tissues are susceptible, you 

 can get very poor results, but when you know something is susceptible, 

 you get very fine results. Some of this ought to be further explored, 

 although I realize that the results by you and van der Camp also indicate 

 this is necessary. 



KLINGSTROM: I think much of the trouble is found in the pine material 

 which is not susceptible enough. I am sorry to say, we have been working 

 for many years with pine materials which are too resistant; so, now I have 

 crossed quite a lot of susceptible pines and made quite a few grafts. I 

 hope that I can have more success from now on, but it's not funny to wait 

 24 months for aeciospore formation. 



KINLOCH. I believe it's understood that susceptibility to Peridermium 

 pini increases with age. Have you tried much older material in your clonal 

 seed orchards or in the wild and have you had more success with or without 

 wounding? 



KLINGSTROM: The old papers say it's only the older pines that are 

 really susceptible, but with these inoculation methods you can evidently 

 break through whatever barriers there may be. I have made a few inocu- 

 lations in old pines which are already attacked with Peridermium pini, 

 and it's very easy to inoculate them. But it's easy to inoculate very 

 small pines too. 



KINLOCH: Would you wound the older pines? 



KLINGSTROM: Yes. 



KINLOCH: That's still necessary even though they are older? 



KLINGSTROM: Yes, I think so. 



KREBILL: Do you think there is some vector relationship involved in 

 infection of Peridermium pini in nature? 



KLINGSTROM: I have seen in nature that the blisters may be consumed 

 by some insect. Now, I just showed this to some entomologists. They shook 

 their heads and could not say what sort of insect it could be. Insects 

 evidently can eat the blister rust and spread away. But I don't know 

 what sort of insect it is. 



KREBILL: We also have insects here that do the same thing. 



