Dec. 9, 191S Seedling Diseases of Conifers 547 



3, is to be considered in connection with Trichoderma. Plate cultures 

 from 30 jack-pine seedlings afifected with blacktop in a nursery in the 

 Nebraska sand hills in every case yielded species of Trichoderma; no 

 such uniformity of occurrence has been encountered for any fungus in 

 any of the series of cultures made from other types of damping-ofif. 



The blacktop type occurs rarely, and, so far as observed, only under 

 unusual weather conditions, most of that observed having followed un- 

 seasonably cold, wet weather. Extensions of the lesions into unaffected 

 tissue stopped simultaneously and abruptly throughout the beds, ap- 

 parently because a change in conditions increased resistance. The 

 affected seedlings were scattered throughout the beds, seeming equally 

 common on acid-treated and untreated areas. The entire picture was 

 that of a disease caused by a fungus which is not strongly parasitic, and 

 is well adapted for aerial dissemination. Trichoderma sp. seems to 

 fulfill both of these requirements, and uniform association with the 

 lesions is believed to indicate causal relationship. The fact that no 

 such lesions have been produced in the few inoculations with Trichoderma 

 sp. does not exclude this hypothesis, as the field evidence indicates that 

 the lesions occur only under very unusual conditions, which are not well 

 enough understood to be duplicated in artificial inoculations. 



PESTAI.OZZIA SPP. 



Species of Pestalozzia have occasionally appeared in cultures made by 

 planting damped-off seedlings in prune-agar plates. In some cases the 

 spores had two dark cells, suggesting P. hartigii. The occurrence of 

 Pestalozzia spp. in cultures from damped-off seedlings has not been suffi- 

 ciently frequent to indicate parasitism strongly. Some interest, however, 

 attaches to the positive inoculation results reported by Spaulding (25). 

 The fact that P. funerea is widespread and common on dead coniferous 

 material and that he succeeded in killing i -month-old seedlings of western 

 yellow pine by inoculation with pure cultures of it indicates that it may 

 be of some importance as a cause of damping-off. His single experiment 

 is the only one which has-been noted on seedlings still of damping-ofif 

 age. Further experiments with it on young pine seedlings are desirable. 

 Its slow growth and rather slow fruiting tendencies would make it rather 

 difficult to demonstrate in diseased seedlings always filled with fast- 

 growing saprophytes, so that failure to obtain it frequently by cultural 

 methods is no proof that it does not occur more or less frequently in the 

 seedlings. 



BOTRYTIS CINEREA 



Botrytis cinerea {B. douglasii, B. •yu/^arw), frequently connected with the 

 damping-off of seedlings of various plants and with needle diseases of the 

 young shoots of coniferous seedlings, does not seem to have been reported 

 as causing damping-ofif of conifers. B. cinerea has never appeared in the 



