J01BAL OF AflMOTRAL BESEARCE 
Yol. XXIX Washington, D. C., November 1, 1924 No. 9 
ALTERNARIA LEAFSPOT AND BROWNROT OF 
CAULIFLOWER 1 
By J. L. Weimer 
Pathologist, Office of Cotton, Truck, and Forage Crop Disease Investigations, Bureau 
of Plant Industry, United States Department of Agriculture 
INTRODUCTION 
In 1918 the writer’s attention was 
called to a disease of cauliflower 2 which 
was causing considerable damage dur¬ 
ing transportation to the market. In¬ 
spectors for the Bureau of Agricultural 
Economics reported it frequently from 
the Chicago and New York markets 
on cauliflower from California and the 
Northwest. The disease probably de¬ 
veloped in transit, since heads said to 
be healthy when placed in the cars 
were badly diseased on reaching their 
destination. From 10 days to 2 weeks 
usually elapse between the cutting of 
the cauliflower on the Pacific coast and 
its arrival in the eastern markets. 
This probably affords ample time for 
the disease to develop. However, there 
was no information available regarding 
the cause of this disease, its origin, or 
the conditions under which it de¬ 
veloped. The investigations discussed 
in this paper were undertaken with a 
view to furnishing such information. 
HOSTS 
Although the brownrot as such 
occurs on only the heads of cauliflower, 
a leafspot caused by the same fungus 
occurs on a number of cruciferous 
plants. The leafspot on cabbage is 
especially well known. The writer has 
been able to obtain infection of young 
seedlings of kohlrabi, Brussels sprouts, 
broccoli, cabbage, and cauliflower in 
the greenhouse. An attempt to infect 
white mustard seedlings failed. A 
number of other closely related plants 
are also hosts for this disease. 
NAME OF THE DISEASE 
The leafspot is usually referred to as 
“Alternaria” leafspot but is sometimes 
called “black”leafspot and“blackmold ” 
The term “brownrot” has been applied 
for the past several years to certain 
brownish-colored lesions of unknown 
origin commonly found on the curds of 
cauliflower on the market. Although 
these lesions do not all have a common 
origin, it is thought that the disease 
here discussed is their most common 
cause. The term “brownrot” is fairly 
descriptive of the disease, and since it 
is already in use by tradesmen it will 
be retained here. But care should be 
taken not to confuse this disease with 
other rots of the curd of this host 
which may also have a brown appear¬ 
ance. One. such rot which is especially 
prevalent and which is most likely to be 
confused with the disease under con¬ 
sideration is of bacterial origin and is 
known by the trade as “slimy softrot.” 
The term “brownrot” was applied in 
the past to a disease caused by Bac¬ 
terium campestre (Pammel) Erw. Sm., 
but the name “black rot” is now used 
exclusively to designate this trouble. 
DISTRIBUTION AND ECONOMIC 
IMPORTANCE 
Alternaria leafspot has a very wide 
distribution, both here and abroad. 
The disease on the curd of cauliflower is 
probably coextensive with the crop 
but is more destructive when the host 
is shipped long distances or is held for 
a considerable period under conditions 
favorable for its development. Putte- 
mans (13 ) 3 in 1911 described what no 
doubt was this same disease occurring 
on curds of cauliflower found on the 
markets of Rio de Janeiro. He 
studied the disease somewhat and de¬ 
cided that it was caused by Alternaria 
brassicae (Berk.) Sacc. The disease 
was found to develop in transit during 
warm moist weather, notwithstanding 
the fact that the time consumed in pack¬ 
ing and shipping the cauliflower was not 
longer than three to four days. The 
writer’s data show that this rapid devel¬ 
opment of the disease may be expected 
at high temperatures and humidities. 
1 Received for publication April 10, 1924—issued January, 1925. 
2 The term “cauliflower" as here used also includes broccoli. 
3 Reference is made by number (italic) to “Literature cited," pp. 441-442 
Journal of Agricultural Research, 
Washington, D. C. 
99186—25f-1 
Vol. XXIX, No. 9 
Nov. 1, 1924 
Key No. G—442 
(421) 
