Pilzkrankheiten der Pflanzen 
43 
a third spraying was given’; The amount of blight on the foliage in the 
second group of tabulated experiments “was slight and so evenly distri¬ 
buted over all of them that neither of the strengths of spray used (l°/o 
and 2%) could be said to possess any advantage over the other ... it 
might be concluded that in a season such as the past one a 1 per cent 
solution would be sufficiently efficacions”. The new fungicide recently 
introduced under the name of Lime-Sulphur solution “was found to be 
utterly useless in warding off the Potato blight”. Steeping seed tubers, or 
sets, in various fungicides before planting was found to be worse than useless 
for as many as 80% of those steeped in copper sulphate solution failed 
to produce plants (less in other cases but always more “misses” than is 
normally the case) and the surviving plants showed not the slightest 
immunity. Experiments were carried out on the effect of heating seed 
tubers affected with blight. It appears from these that it is “possible 
to eliminate or destroy Phytophthora in potato tubers by heating them to 
about 50° C without doing any serious damage to the tubers themselves” 
particularly if these are only slightly affected at the outset. Two varieties, 
“Shamrock” and “Clifden Seedling”, were again found to be fairly immune 
as regards leaf attack and no diseased tubers were found. In experiments 
where diseased tubers were planted it was found that over half died in 
the ground but that the remainder produced slightly weak but perfectly 
healthy plants. Another experiment “would seem to show that potato 
tubers do not become infected with blight from the soil in the absence 
of a supply of spores from affected foliage over head”. 
Experiments were also conducted on the disease caused by Sclerotinia 
sclerotiorum. Experiment showed that in the treatment of this disease 
there is no advantage to be gained by adopting the method of planting 
in drills. No method was found which appeared to be of any avail in 
reducing the amount of disease but there were indications that attacks could 
be avoided by late planting. (Observations are also recorded on Bacillus 
melanogenesl) An account of the effects of Spo?igospora subterranea is 
given. Experiments begun in previous years were continued. It had been 
previously shown that by suitable treatment of affected seed a clean crop 
could be grown, providing the land used was free from the organism. 
Experiments showed that various substances were efficacious in reducing 
the amount of disease but reduced the total yield to a greater or less 
extent, CuS0 4 was the best for reducing the amount of disease but 
considerably reduced the total yield. Sawdust, KC1 and K 2 S0 4 seemed to 
reduce the amount of disease without interfering with the total yield. 
Plants suffering from “leaf-roll” and “curl” are distinguished. 
Verticillium alboatrum is very frequently (but not always) found in plants 
suffering from leaf-roll not only in the stalks, but also in the leaves, roots 
and tubers. An infected tuber was divided into portions and planted and 
all the resulting plants contained the fungus in all their parts and succom- 
bed. In other investigations have shown that the tubers produced from a 
diseased one do not all of them necessarily contain the fungus. More often 
it is in the older and larger tubers. In some plants suffering from leaf- 
roll no fungus could be discovered. Tubers derived from such plants 
gave plants which were practically free from leaf-roll and in which no 
fungus was present. “From these and other observations it would seem 
as if there might be two kinds of leaf-roll, one non-parasitic and the other 
