HAT 



JOB 



15 



JU.r 



90 



feximiB d*ily 80 



tcaparatur* 



70 



(d«CTMi 



60 

 SO 



1 



p/W 



Y^ 



60 

 AT*ra<« «««kl7 



ipor* c*»t 40 



(par 1.67 »q. — .) 



20 









90 



KiHu <Ully SO 



r«l»tl« hwidlty 



70 

 - Mrt] 



60 

 50 



A 



|wy\T\A 



yujv 



Ik.. 14. — Ascospore discharge at the Cortland plantation, 1956. Maximum tem- 

 perature and relative humidity are plotted on a daily basis. The center graph 

 shows the number of ascospores deposited, per 1.67 sq. mm. of slide, per week. 

 Each weekly plot is the average of 12 slides. 



increase in spore liberation occurred. It is interesting to note that 

 this increase occurred during a week of high relative humidity. 



The first ascospores were found at Cortland on June 4 (Fig. 14). 

 The initiation of spore casting and the peak of sporulation were 

 coincident with periods of high relative humidity. The peak sporu- 

 lation was reached at Cortland on July 9, nearly two weeks later 

 than at Camden. 



There was little relationship between time of ascospore discharge 

 and temperature. The temperature at both areas fluctuated continu- 

 ously, with no extremes in either direction lasting longer than two 

 days. The average maximum temperature for June and Julv at 

 Cortland was 80 C F.. while that at Camden was 76°F. 



INFECTION 



The parasitic nature of Rhab doc line pseudotsugae and its abilit\ 

 to attack the needles of the most vigorous trees as frequentlv as 

 those of diseased or suppressed trees is well known (29, 66, 70). 

 The exact nature of infection, however, is still not clear. 



