AKTIFICIALLY SPREADING FUNGOUS DISEASES. 49 
During 1909 about 2,000 trees were included in the experimental work 
conducted. 
Various methods have been employed in experimental work in the 
artificial dissemination of the fungous diseases. The tree-planting 
method recommended by Dr. Webber and Prof. Gossard and the 
leaf -pinning method commonly employed previous to 1907 have both 
been tested as checks on other methods. Spraying water mixtures 
of spores of the red and yellow Aschersonias, winch, as heretofore 
stated, was first successfully used and recommended by Dr. Berger, 
has been most extensively used, as this method has proved the most 
satisfactory for use on a large scale. Preliminary tests of using water 
mixtures of spores in September, 1906, by the senior author seemed 
to show that the spores were affected by pressure in passing through 
an atomizer or spraying nozzle. 1 
Consequently, two other methods were used which, so far as known, 
had not been previously tested. These methods, with their various 
modifications, have been called the dipping and the brushing methods. 
Aside from the tree-planting and leaf-pinning methods and the 
methods mentioned in connection with the dissemination of fungous 
infection by means of water mixtures of spores and mycelia, the 
authors have tested and in correspondence recommended for Use the 
rubbing of the underside of infected leaves against the underside 
of the leaves of uninfected trees. This has been done both with 
single infected leaves and with twigs with several infected leaves 
attached. It has also been tested with dry and wet leaves. The 
rubbing method has been most extensively used in experiments in 
the dissemination of the brown fungus. 
PINNING AND RUBBING INFECTED LEAVES. 
The pinning of infected leaves in introducing the Aschersonias, 
being obviously an inferior method, has been used by the authors 
principally in the form of checks on other methods tested. Infection 
was not secured in more than 50 per cent of the experiments, and 
when secured was a more local infection than those following spraying. 
Better results followed when the upper surface of the fungous leaf was 
brought into contact with the underside of the leaf to which it was 
pinned, although good infections have followed when the fungus 
pustules have been placed against the leaf. In all instances where 
infection followed pinning, fungus developed either on the leaf to 
which the fungous leaf was pinned, or more often on leaves immedi- 
ately below, and occasionally on leaves so located that they might 
have been brushed against the fungous leaf by winds. In view of the 
greater abundance of infections occurring immediately below the 
* Later experience indicates that the unsatisfactory results obtained were due to lack of suitable weather 
conditions. 
21958°— Bull. 102—12 4 
