DAMPING-OFF IN FOREST NURSERIES. 65 
rious strains of Botrytis, both from conifers and from other hosts 
(the latter supplied by the departments of plant pathology of the 
California and Xew York (Cornell) Agricultural Experiment Sta- 
tions), have already yielded confirmatory evidence of the parasitism 
of B. cinerea. 
While a considerable number of fungi have been considered in the 
foregoing, it is entirely possible that there are still ^parasites which 
have received no consideration and that some of them may perhaps 
be important. The moist-chamber method of cultnring . parasites 
for isolation yields only those which produce spores readily; the 
planted-plate method is not well adapted to the isolation of slow- 
growing fungi or bacteria. It is suggested that in further culture 
work with damped-off conifers an attempt be made to secure slow- 
growing organisms by dilution plates of teased-up fragments of 
recent lesions. 
RELATIVE IMPORTANCE OF THE DAMPING-OFF FUNGI ON 
CONIFERS. 
The relative importance of the different damping-off parasites is 
something that has not been thoroughly investigated for any host. 
The most information on this point is that given by Busse, Peters, 
and Ulrich (22) for sugar beet. In this case they find the special- 
ized PJwma hetae distinctly the most important, with Pythium de- 
baryanum second and AphariGmyces levis third. 
Peters (100) apparently considered Phizoctonia unimportant as 
a cause of beet damping-off. The opposite was indicated by a small 
number of cultures by Edson (38) from beet seedlings on Kansas 
and Colorado soil. These yielded more Corticium vagum than any 
other parasite and no Pythium at all. Johnson (81) states that 
most of the damping-off of tobacco seedlings is due to Pythium 
debaryanum and Corticium vagum. Atkinson (1), speaking for 
cotton in Alabama, and Sherbakoff (127, p. xcv; 128; 129), speak- 
ing for truck crops in Florida, make Corticium vagum the impor- 
tant damping-off parasite, with P. debaryanum negligible. Home 
(oral communication) found the same situation in tobacco seed 
beds in Cuba. Atkinson (3), in an article on trees, held that many 
of the cases of damping-off attributed to P. debaryanum are in real- 
ity due to C. vagum. Peltier (98, pp. 336-337) has reported Phi- 
zoctonia solani as the cause of damping-off of a large number of 
plants, recording his observation of the damping-off of seedlings of 
nearly 50 species of miscellaneous genera and cuttings of 13 different 
species, all of which he attributes to the Phizoctonia. He does not 
state whether in this case he used diagnostic methods likely to de- 
tect Pythium debaryanum if it had been present. 
19651°— Bull. 934—21 5 
