A NEW APPROACH 
Gladiolus Disease Control 
The control of glad diseases is a 
several-million dollar problem, and 
can not be safely ignored. One ap- 
proach to solving it is presented here 
by Robert O. Magie, pathologist of 
gladiolus investigations of the Agri- 
cultural Experiment Stations of the 
University of Florida. It is endorsed 
by E. H. Price, Jr., manager of the 
Florida Gladiolus Growers Associa- 
tion. 
HE MOST destructive gladiolus 
T disease is caused by a soil-borne 
fungus, Fusarium oxysporum f. 
gladioli Sny. & Han. The annual loss 
of flowers and corms due to this 
disease is over $3 million, possibly 
$5 million. Growers of cutflowers 
in Florida alone suffered a loss of 
one and one-half million dollars this 
past season. Measures that were ef- 
fective in controlling Fusarium rot 
a few years ago are much less ef- 
fective in Florida since 1947-48. Av- 
erage corm losses in the Picardy va- 
riety increased from about 12 to 33 
per cent between 1946 and 1950. 
New strains of the Fusarium fungus 
may account for much of this in- 
crease. 
It is obvious to anyone familiar 
with the gladiolus industry that the 
Fusarium disease is not adequately 
controlled by treating the corms 
with fungicides. Furthermore, it can 
be stated now that the disease will 
not be satisfactorily controlled with 
resistant varieties, as we know 
them, until species or relatives of 
gladiolus immune to Fusarium are 
found and this immunity is combin- 
ed by breeding with the horticul- 
‘tural characteristics of important va- 
rieties, such as Picardy. New va- 
rieties, as well as old, are succumb- 
ing to more virulent strains of the 
ever-changing fungus. Even Maid of 
Orleans variety is susceptible to a 
new Fusarium strain isolated from 
the Spic and Span variety. 
The Missing Link 
Fungicidal treatment of corms and 
disease resistance are, of course, nec- 
essary parts of the disease control 
program, but something more is 
needed. The missing link is disease- 
free propagating stocks. Just as the 
potato industry saved itself years 
New, virulent strains of pathogens have wreaked 
havoc with the gladiolus industry. The old 
controls are no longer enough 
ago by producing certified planting 
stock, so must the gladiolus industry 
now segregate and maintain disease- 
free propagating stocks. These spe- 
cial stocks, maintained by a few 
growers, would serve as reservoirs 
of healthy planting stocks for all 
bulb growers. 
The great need of healthy propa- 
gating stocks is highlighted by the 
Picardy variety. To replace their 
heavy disease losses in this variety, 
Florida growers have been buying 
annually over 25 million corms of 
Picardy from northern and western 
bulb growers. In practically every 
case they got diseased stock; that is, 
a portion of the corms carried Fu- 
sarium infection in a dormant state. 
Because their Picardy stocks are 
badly depleted and can not be re- 
placed with healthy corms, growers 
are turning to other varisties. How- 
ever, Picardy is still the most desir- 
able variety for cutflower shipping. 
Contrary to what many _ people 
think, Picardy is as good a variety 
as it ever was, except perhaps for 
unknown or obscure virus infections. 
The variety has not “run out.” 
Temperature Relationship 
Picardy corms shipped from north- 
ern or western states have an aver- 
age of about ten per cent of the 
plants affected with Fusarium two 
months after planting on new land 
in Florida. Stocks from other coun- 
tries have not been tested. Treat- 
ment of the corms with Lysol or 
N.I.Ceresan solution before planting 
only delays the appearance of rot- 
ting. These corms appear to be 
healthy when planted in Florida. 
They rot because the Fusarium in- 
fection was carried in the corms in 
a latent condition in the core region. 
They are apparently caused by 
weaker strains of the fungus, and 
under growing conditions in the 
Southeast these less virulent strains 
usually cause rotting. 
It may be that Fusarium strains 
differ in temperature requirements. 
It is believed that latent infections 
of Fusarium explain many cases of 
poor flower production in certain va- 
rieties. 
Picardy corms from various parts 
of the United States were grown on 
new land in Florida. In testing num- 
erous lots of Picardy, the writer 
found only one commercial source 
of Fusarium-free corms. This source 
is in the region of Pacific and Au- 
burn in western Washington. Fusar- 
ium infection has disappeared from 
diseased corm stocks after growing 
them in that region for two or more 
years. There are some facts to sup- 
port the theory that the absence of 
Fusarium disease in fields near Pa- 
cific and Auburn is due to the low 
temperatures that prevail there 
through the growing season. Dr. C. 
J. Gould of the Western Washington 
Experiment Station at Puyallup is 
interested in the problem and hopes 
to have more positive information 
on it. Presumably other regions 
with growing seasons of closely sim- 
ilar climate would also be suitable 
for cleaning up Fusarium-infested 
planting stocks. 
Some samples of Picardy from 
small and non-commercial growers 
also proved to be free of Fusarium. 
These and the thousands of Picardy 
corms purchased in each of the past 
three years from western Washing- 
ton were grown in Florida without 
Fusarium infection as long as they 
were planted on disease-free land 
and treated to prevent infections 
when the corms were cleaned. It 
was also found that these disease- 
free corms could be grown on infest- 
ed land with relatively light losses 
from disease for the first year or 
two. 
Cost of Disease-Free Stock 
Fusarium yellows and corm rot re- 
duce the quality as well as the quan- 
tity of flower production. The cost 
of producing flowers from diseased 
stocks is high compared to produc- 
tion costs with healthy corms. At 
any reasonable price, disease-free 
corms of some commercial varieties 
are not generally available from 
bulbs growers. Florida cutflower 
growers are being forced to develop 
and maintain their own planting 
stocks in order to stay in business, 
even though most of them prefer to 
buy their corms. As a matter of 
fact, flower growers tend to be poor 
growers of planting stock because 
their main interest lies in flowers. 
