486 
I~ttinors NATURAL History SuRVEY BULLETIN 
Vol. 26, Art. 6 
Table 18—Results of greenhouse tests on gladiolus variety Picardy inoculated with 
Fusarium, 1948. 
Symptoms AND NumMBERS oF CorMs AFFECTED 
ISOLATE 
Vascular 
Discoloration 
4e 
an 
' 
wv 
ooocooocooocooocon 
Basal Dry Completely No 
Rot | Destroyed Symptoms 
0 0 4 
1 5 
0 0 10 
0 0 10 
3 1 6 
7 1 2 
0) 0 10 
0 10 0 
1 1 8 
9 0 1 
0) 10 0 
0 10 0 
8 2 0 
0 0) 10 
differences in results, especially in the case 
of the variety Rosa Van Lima, which de- 
veloped rot in 1951 but not in 1952. The 
over-all results seem to indicate that, as has 
been reported for many other pathogenic 
organisms, the isolates lose their virulence 
when maintained in laboratory culture 
over a period of time. More precise tests 
over a longer period of years would be 
necessary to establish this point with cer- 
tainty. 
Greenhouse Tests 
In the greenhouse, corms were planted 
in soil which, after being steamed, had 
been infested with cultures of Fusarium 
that had been grown on autoclaved whole- 
grain oats in 250-milliliter Erlenmeyer 
flasks for 2 to 3 weeks. The flasks were 
shaken daily during the growth period of 
the Fusarium. 
In order that the chances of using in- 
fected gladiolus corms in these experi- 
ments might be minimized, the husks were 
removed and the corms were soaked 15 
minutes in a solution of 9 grams New Im- 
proved Ceresan (5 per cent ethyl mercury 
phosphate) in 1 gallon of water. The 
corms were then washed in several changes 
of tap water to remove the Ceresan. Cor- 
mels used in some of the tests were treated 
in this same way. 
Furrows 214 to 3 inches deep were 
marked out across a greenhouse bench. 
Depressions + inches apart were made in 
the bottoms of the furrows. One Fu- 
sarium-carrying oat grain was placed in 
each depression and covered lightly with 
soil. A gladiolus corm was then set over 
it. After the corms had been placed, the 
furrows were filled with soil. 
No attempt was made to maintain a 
constant soil moisture content. Water 
was applied to the soil as often as neces- 
sary to maintain good growing conditions. 
Tests in 1948.—Preliminary tests with 
13 isolates of Fusarium were made in 
1948. Ten Picardy corms, each approxi- 
mately three-fourths inch in diameter, 
were used for each isolate. Planting was 
done March 1. All corms produced new 
plants. By April 19, yellow leaves indi- 
cated disease in some of the plants. New 
corms were examined August 5. Symp- 
toms produced by the different isolates and 
the numbers of corms affected are shown 
in table 18. 
Tests in 1952.—Twenty isolates of 
Fusarium were tested in 1952 for patho- 
genicity on the varieties Dr. F. E. Ben- 
nett, Margaret Fulton, Picardy, and Vari- 
ation. Ten commercial size No. 5 (one- 
half to three-fourths inch in diameter) 
corms of each variety were used with each 
isolate. Three groups of checks, each con- 
sisting of 10 corms of each variety, were 
used in this experiment. 
Planting was done on February 21 and 
22. Differences in reaction of the four va- 
rieties to some of the isolates were quite 
pronounced by April 14, figs. 20 and 21. 
i 
