Mar. 3, 1Q33 
Gray Mold of Castor Bean 
711 
All the applications used controlled the disease to some extent, as can 
be seen at a glance. The failure to get anything like complete control 
was undoubtedly due not so much to the ineffectiveness of the fungicides 
against the parasitic mold as to the extreme rapidity with which the 
plants grew and exposed unprotected surfaces to infection by the myriads 
of spores that were present at all times. New buds would unfold over¬ 
night. Young inflorescences would double in size in 48 hours. Male 
blossoms would open up, uncovering the anthers, thus multiplying the 
exposed surface many fold and in addition furnishing ideal conditions 
for infection. Young pods themselves would rapidly increase in size 
and expose unprotected surfaces. It is evident, therefore, that spraying 
is out of the question in so far as practical control of the disease is con¬ 
cerned. Three or four sprayings during the season would be impracti¬ 
cable in so far as expense is concerned, to say nothing of the two or more 
applications per week that would be necessary to produce results. 
SEED-TREATMENT 
It has been shown that this destructive disease was carried into America 
by means of the seed and that the seed is perhaps its most important 
carrier from one section to another. A seed treatment that would 
destroy the fungus without injuring the seed would therefore be a step 
toward prevention of the disease. In a seed-treatment experiment 
carried out in March, 1918, at Orlando, Fla., lots of 200 seeds each were 
given the following treatments: 1 to 240 formaldehyde (commercial 40 
per cent formalin) for 5, 10, 15, 20, 30, 45, and 60 minutes, and murcuric 
chlorid 1 to 1,000 for equal periods. After the treatments, the seed were 
planted in rows, under natural conditions. A month later a careful 
count was made of the germination and growth in each row. The 
results are given in Table III. 
Table III .—Germination of seeds treated with formaldehyde and mercuric chlorid 
Period of treatment (minutes). 
Percentage germination. 
Formalde¬ 
hyde. 
Mercuric 
chlorid. 
68.5 
53-5 
63 
55 
60. 5 
64 
67-5 
73 
57-5 
55 
67 
63.5 
74 
7 i 
1 cr. 
60. 
A frost on April 1 undoubtedly killed some of the plants, but the 
results are roughly comparable. For either treatment, germination 
was practically as high for 60 minutes’ immersion as for 5. It is there¬ 
fore certain that no injury is likely to be done the seed by any reasonable 
chemical treatment. 
Seeds formed in an inflorescence that has been attacked by the gray 
mold are lighter in weight than normal healthy seed; in fact the worst 
of them are so lightfas to be blown out by the blower in a seed-cleaning 
machine.§| The castor beans shown in Plate 7, E, are examples, light in 
weight and worthless as seed. The living fungus inside the tough seed 
27184 — 23—-3 
