C”akne — Brown Hot of Citrnfi. 
'M 
iiio' tli-e j>Touii(I. Spores are formed and infection takes place onlv 
during or immediately folkming wet Aveatlier. Infection is 
greatest on the sides of the frees most slieltered as it is there that 
tile leaves or fruits most frequently remain wet long enough to 
alloAv tlie conidia to ge-i-minate and bring about infection. The 
incubation period is about 10 days. During or following wet weatln.-r- 
the affecte<l jiarts of ti'ees produce conidia Avliicli infect other j'tarrs 
of the same plants or are carried by Avind to other trees. Infe<'te.l 
leaves and fruits fall to the ground, and there jAroluce oos]>ores. 
Tnfection ceases al)out October with tiie rise in temperatures. 
This suggested history already given elsewliere (6) lacks con- 
firmation on one point namely the germination of the oospores Avhich 
has not yet been observed. 
The disease does not spi’ead in store' or case fast enough to ho 
a serious consideration in the local trade. This spreading may be 
more important in -exported fruit. Ko evidence has been obtaiiud 
of mycelial infection between fruits. The indications point to infec- 
tjon taking pla<a^ from conidia borne/ on the fruits, Avhieh is, of 
course', possible only when tliey are damp. There is also no evidence 
of the disease carrying over in the tAvigs. Many cases liaA^e beeii 
noted of defoliated branches )>i*odncing clean shoots 
CONTROL. 
Excellent control has been obtained by spraying citrus trees 
Avith Bordeaux Mixture (4 — 4 — 50) , or Burgundy Mixture (4 — 6—50') 
in A])ril or early in May before the Aviuter rains. This subject has 
been dealt Avith in more detail elseAvhere (6 & 8) , 
It is recommended that the ground under the trees be sj)rayed 
and that the spray be applied to the trees only to a height of four 
feet. This has l)tHm found to give excellent results, and all the same 
time reduces the danger of the rapid increase of scale insects aim 
a,])hides Avhich unfortunately fre(iuently folloAA'S the- use of fungi- 
cides on citrus trees. 
The Avriter desires to express his appreciation of the assists ik-c 
received from many sources. Especially is he indebted to Dr. E . J . 
Butler. Imperial Bureau of ^lycology, for references to literatu: e, 
a ti'anslation of iloniz da Maia ’s ])aper, and a very helpful interest, 
to Mr. W. 1j . Wat-erhouse. B.Wc., Agr.. Sydney University, for 
lielpful criticism; to Mr. G. Wickens, Officer in Charge of Fruit 
Industries, Department of Agriculture, and his Inspectors, fov 
assistance , in the field ; to Mr. J. G. C. Cani])bell, B.Se., hU 
nssistant in 192.1, Avho first isolated the organism in ]>ure culture; 
to Mr. C. A. Gardner, for redraAving camera Incida draAvings ; to 
^ir. J. Clark, for assistance in making microphotographs ; and t'> 
IVIr. A. C. R. Loaring of Bickley on Avhose orchard most of th. 
field Avork Avas done. 
