Feb. 15, 1925 
Control of Mycelial Neck Rot of Onion 
373 
Table V. —The effect of artificial drying upon the development of mycelial neck 
rot in large bulbs of White Portugal and White Globe varieties, 1917 and 1923 
Lot 
No. 
and 
year 
History of bulbs previous to 
experiment 
Subsequent 
treatment 
i 
Crate 
No. 
- 
Condition at 
end of storage 
period 
Length of 
drying period 
Total 
num¬ 
ber of 
bulbs 
Bulbs 
decayed 
with 
neck 
rot 
Bulbs 
show¬ 
ing in¬ 
cipient 
neck 
rot 
com¬ 
pletely 
checked 
Per cent 
Per cent 
III 
rTfi treated 
17 
304 
36 
1917. 
from Lots I and II (see 
In drier 7 days 
18 
301 
.6 
Table IV), U to If inches 
(81 hours 
in diameter. 
. above 90° F.) 
Untreated 
19 
437 
44 
0 
20 
2J days at room 
1,093 
9 
19 
IV 
White Globe large onions, 
temperature 
1923. 
grown on old onion soil; 
and 6 hours at 
harvested about Sept. 10, 
In drier (with 
40° C. 
cured in bushel crates 
forced cireula- 
21 
3 days at room 
630 
5 
37 
about three weeks, then 
tion of air). 
temperature, 
placed in drier Oct. 2. 
3 hours at 44° 
p 
22 
V. 
_do_ 
515 
7 
21 
The experimental evidence shows 
that mycelial neck rot may be largely 
prevented by thorough desiccation of 
the neck tissue of the bulbs within the 
first two to three weeks after harvest. 
It is shown that this may be accom¬ 
plished by exposing the bulbs to higher 
temperature, by exposing them, to 
forced air currents, or by a combina¬ 
tion of the two methods. The prin¬ 
ciple of this measure of control seems 
to be sound. There remains to be 
worked out details whereby artificial 
curing can be applied on a large com¬ 
mercial scale with satisfactory rapidity 
and at a reasonable cost. 
It is desirable that this investigation 
be extended to include the gray-mold 
neck rot Botrytis allii. Although 
this disease is ordinarily of minor con¬ 
sequence in the Illinois and Wisconsin 
sections, it is nevertheless widespread 
in its distribution and often causes 
serious losses in other sections. The 
life history of the causal organism is so 
similar to that of mycelial neck rot that 
the same methods of handling would 
probably lead to effective control. 
SUMMARY 
(1) The mycelial neck rot of onion, 
caused by an undescribed species of 
Botrytis, herein referred to as Botrytis 
sp. 110, is a common cause of heavy 
storage losses of onion, especially of the 
white varieties. This paper is con¬ 
cerned with the relation of certain 
methods of handlin g the onion crop at 
harvest and in storage to infection and 
to the control of the disease. 
(2) When removal of onion tops at 
harvest is practiced, the state of ma¬ 
turity of the plant has a direct bearing 
upon the amount of infection. In the 
experiments with the Red Globe variety 
the percentage of bulbs infected was 
doubled in the case of lots in which the 
neck tissue was still succulent at time 
of harvest as compared with those in 
which the tops had matured properly. 
(3) In the case of colored varieties 
the removal of tops as compared with 
allowing them to remain intact after 
harvest usually resulted in greater 
infection. In the one experiment with 
White Globe variety there was little 
difference to be noted. 
(4) Artificial curing of onion bulbs 
sufficient to cause desiccation of the 
neck tissue within two or three weeks 
after harvest has resulted in all cases in 
a material reduction in the amount of 
disease. This treatment promises to 
become an effective control measure, 
provided it can be adapted to commer¬ 
cial use at a reasonable cost. 
