22 
Carxe — Brown liot of Citrus. 
The disease was last noted active early in September. 
During the season it was again recorded from all citrus areas, 
thougli (fwing to tlie exceptionally dry winter the losses in general 
were lighter than those of .1924. 
Tlie same |iatliogen as in the two ])reviou?) seasons was again 
isolated many times from lemon leaves and fruit as well as from 
tlio leaves ami fruit of oranges and mandarins. It was also isolated 
from an orange from Soutli Australia. Infection of oranges and 
lemons was secured from the 1924 isolations from orange leaves. 
Oranges and lemons were infected from cultures from each otle.?r 
and from leaves. Definite evidcmce was secured that Drown Dot on 
oranges and lemons and their leaves in Western and South Australia 
were due the sanu' cause. Investigations carrietl out late in tho 
season of 1924 had seemed to indicate that the lemon diseases were 
due to different pathogens ((>) . This Avas found to be incorien-t. 
MET7fOl)S OF ISOLATION. 
Successful results have been obtained by spreading a Avatc'-r 
sns])ension of spon>s from affected tissues on j’otato dextrose agar 
2 )lates and ])i(‘kiiig off germinating spores. Usually, however, 
isolation has been obtained by Avashing small pieces of affected 
leaA’es in corrosi’-e su]>limate solution (I-IOOO) for one to tlir'^o 
minutes, followed by three wasliings in sterile tap Avater. and tlien 
})]aciiig on potato dextrose agar plates. Some fruit isolations Avere 
made i]i tlie same Avay after tirst washing tlie fruit in Avater, an>i 
then Avith alchohol, and cutting out Avith a sterile scapel small por- 
tions of the surface tissues at or just beyond the tnlges of the- evi- 
dent lesions. Dest results Avere obtained 1>a' inA'erting tliese jiieces 
of tissiu' so that the surface of the fruit came iu contact Avitli the 
agar. Pieces taken beyond the edges of the lesions gaAm the 
lowest contaminations. After two or three days the mycelium 
could be easily recognised by its characteristic dense branching, AA'lian 
examined under a Ioav power through the underside of tlie petri 
disli. A])])areiitly clean groAvth aa'US then jiicked off on to agar 
plates. Contamination from liacteria has been the most difficult 
to avoid, the use of latic acid in thei medium lieiiig unsatisfactory 
owing to the inhibition of the fungus. Repeated sub-culturing has 
<)ften been necessary. Isolation from fruits in an adA'aneed stage 
and obA'iously much contaminated Avith secondary organisms lias 
been obtained by transplanting portions of the least infected tissues 
into sound fruit, and then making cultures front the latter as soon 
as infection lieeame e\'ideut . In general^ hoAA’ever^ it has been con- 
sidered sufficient to recognise the fungus iu such cases and not to 
attempt isolation in pure culture. It lias been found possible 
1o readily recognise the mycelial groAvth as it differs considerably 
from that of Pythiacystis or Phytophthora terrestris (Plate II). 
