ARTIFICIALLY SI'HKADINd FUNCOUS DLSEASES. 49 



During 1909 about 2,000 trees v,'vvo. included in 1 lie ex])eiimental work 

 conducted. 



Various methods have been oinployod in experimental work in the 

 artificial dissemination of the fungous diseases. The tree-planting 

 motliod rocomnuMuh'd by Dr. Webber and Prof. Gossard and tlie 

 loaf-j)inning methotl commonly employed previous to 1907 have both 

 been tested as checks on other methods. Spraying water mixtures 

 of s])oros of the red and yellow AscluM'sonias, wliicli, as heretofore 

 stated, was lu'st 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.^ 



Consequently, two other metliods were Used which, so far as kno\\Ti, 

 had not been previously tested. These methods, with their various 

 modifications, have been called tlic dippuig and the briishuig methods. 



Aside from the tree-planting and Icar-pinning methods and the 

 methods mentioned in connection with the dissemination of fungous 

 uifection b}' means of water mixtures of spores and nn^celia, the 

 authore have tested and in correspondence recommended for use the 

 rubbing of the underside of infected leaves against the undereidc 

 of the leaves of uninfected trees. This has been done both with 

 suigle 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 pummg of infected leaves in introducmg the Aschersonias, 

 being obviously an inferior method, has been used by the authors 

 principally in the form of checks on otiier 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 followmg 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 

 pmned, although good uifections have followed when the fungus 

 pustules have been placed against the leaf. In all instances where 

 infection followed pimiuig, 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 bruslied against the fungous leaf by winds. In view of the 

 greater abundance of infections occurring immediately below the 



1 Later expericncG indicates that the unsatisfactory rjsults obtained were due to lack of suitable weather 

 conditions. 



21958°— Bull. 102—12 4 



