H. WORMALD 99 



angia were observed in this experiment either on the infected apples or 

 pears, but all produced sexual organs similar to those found on the 

 naturally infected fruit and in cultures. 



The morphology of the fungus causing this rot of pears and apples, 

 particularly with respect to the sexual organs and the sporangia, con- 

 forms to that of Phf/tophthorn Cactonim as given by Rosenbaum (lO) 

 who has recently made a comparative study of the genus, and as this 

 fungus has been identified as causing a similar rot on pears and apples 

 on the Continent and on apples in America it is to be concluded that 

 the disease occurring in this country is identical with that found abroad. 



Control Measures. 



Since the fungus continues to develop on the fallen fruit these 

 should be collected and burnt; fruit rotting on the trees should also be 

 removed and destroyed. These precautions would tend to keep the 

 disease in check by eliminating centres of infection, but in general 

 would only be practicable on a small scale, as in gardens and small 

 orchards. 



As the outbreaks hitherto reported in this country have been sporadic 

 and locahzed, and as the disease appears to be serious only during very 

 wet weather at the time the fruit is approaching maturity, experiments 

 with a view to controlling the disease by spraying have not been 

 attempted. From analogy with other diseases caused by members of 

 the Peronosporaceae it is probable that Bordeaux Mixture would be an 

 effective wash as a preventive against infection, and in fact has been 

 recommended for this disease by Marchal(3). The formula 4:4: 50, i.e. 

 4 lbs. copper sulphate, 4 lbs. quicklime, to 50 galls, of water, gives a 

 Bordeaux Mixture suitable for pear trees and many varieties of apples, 

 and should be given a trial in the event of a threatened epidemic of the 

 Phytophthora rot. 



SUMMARY. 



In wet seasons Phytophthora Cactorum (Lebert et Cohn) Schroter 

 sometimes produces a rot of apples and pears in this country, causing 

 the fruit to fall. 



The rot in pears is characterized by a dark brown discoloration of the 

 affected tissues accompanied by the appearance, at the surface, of clusters 

 of sporangia, seen with the naked eye as glistening particles. 



In apples the discoloration is paler and sporangia are less readily 



