Carxe — Brown Bot of Citru.<i. 
1') 
SYMPTOMS OF BROWN ROT DUE TO PHYTOPHTHORA 
HIEERNALIS COMPARED WITH THOSE OF PYTHIA- 
CYSTIS BROWN ROT. 
Bi'own Rot in California due to Pijthiaei/stis citrophthora Avas 
descriixMi by R. E. & E. H. Smitli as essentially a lemon fruit disease 
oeeurring less frecinently on oraiii^’es, mandarins^ pomelos, etc., 
{29 & ;i0). In a letter to the rvriter Professor H. S. Eaweett, of 
tlie Citrus Ex 2 )eriinent Station. University of California stated “'we 
sometimes find the Ppthiacysti.s fungus attacking- tlie leaves, but this 
is not so frequent as the attack of the fruits, especially lemon fruits, 
although oranges are also attacked vhen the ■weather is very moist 
and there is a medium temperature over a considerable period.^' 
Pythiacustis Bianvii Rot would therefore appear to be essentially 
a. lemon fruit disease attacking' oranges less frecpiently and citrus 
leaves even less. PhytoplitJiora hibernalis on the other hand in 
■Western iVustralia attacks leaves more frecpiently than fruit, and 
orange and mandarin fruits more frequently than lemons. There 
are undoubtedly great resemblances between the two diseases, .it 
may be mentioned that oranges were infected by the writer with 
pure cultures of }^ythiacysti.<i ci tro])Jifhora and Pytopliiliora ierres- 
fris Sherb. [probably a form of P. parasitica Bast. (1 & 17) ] 
developed Brown Rot not distinguishable from that due to 7^. hibern- 
alis. Tliese two cultures Avere obtained from California through the 
courtesy of Professor Eaweett. Tliough P. terrrstris causes a citrus 
stem gummosis in Florida and elseAvhere (Id) it has not, so far as 
the Avriter is aware been found in nature on citrus fruits. A further 
resemldance betAveen the (Californian and the Australian diseases is to 
be found in the fact that both deA^ePq) under conditions of high soil 
moisture content, especially in AA*et Aveatlier, in Ioav A\'et situations and 
on the loAver and sheltered portions of the trees. Further differ- 
ences ina.v be noted Avhich cannot be related to the climatic differ- 
ences in the two countries, Pythiacystis BroAvn Rot remains active 
throughout the summer Avhere tlie ground isf Avet according to Smith 
(30). This is unknown in Australian Brown Rot, CA^en in orchards 
alongside perennial streams. The Australian disease is essentially 
one of cool-moist Aveather, Heavy defoliation, tAvig blight and con- 
sequent failure to bloom and fruit are not recorded in California. 
Pythiacystis BroAvn Rot spreads readily, in packed fruit. With the 
Australian disease, infection spreads sloAvly, and only under very 
favourable conditions. No loss is experienced from this cause In 
Western Australia, though this appears to be the most important 
feature in the American rot. 8o far comparisons liaA^e been made 
only Avith the symptoms of Pythiacystis BroAvn Rot as stated to 
occur in California. 
Published descriptions by Cole (10) of the symptoms of Pythia- 
cystis BroAvn Rot in Victoria agree exactly Avith those of the Phy~ 
