Aug. i, 1921 
Two Sclerotium Diseases of Rice 
655 
weakened or slow-growing condition are very susceptible to attacks by 
parasitic organisms, a fact which probably accounts for the higher per¬ 
centage of the disease in early sowings. 
The fungus requires considerable air for its growth and consequently 
does more damage to rice seedlings when the soil is rather dry. Reinking 1 
states that— 
When there is a lack of water in seed beds, the disease appears to be at its worst. 
Seed beds should be kept flooded. 
When the land is irrigated the growth of the fungus is checked and 110 
further damage is caused, while all plants recover that are not too nearly 
dead. If the disease begins to develop, the field should be irrigated as 
soon as possible. Observations, both in the field and in sowings made in 
inoculated soil, reveal the fact that the disease is completely checked by 
water. If the soil of a field is known to be infested, a much better stand 
may be obtained by irrigating the land sufficiently to wet it thoroughly 
at the time the seed is germinating. This would tend to hold the fungus 
in check at the most critical stage in the seedling growth, as shown in 
Tables I and II. These experiments showed that the greatest injury 
was done before the seedlings emerged from the soil. 
To control the spread of the disease the rice grower should prevent 
irrigation water from flowing from infested fields to clean fields and avoid 
taking rice straw or hay from fields where the disease occurs and putting 
it on other soil, as the organism may be growing saprophytically on such 
dead material. Although the fungus from the soybean proved much 
less parasitic on rice than did the rice form, it is still possible for the rice 
fungus to be carried on the the soybean plants. It may also be carried 
as a saprophyte, and it is advisable to select clean bean seed, especially 
if it is to be sown on uninfested land. 
STEMROT CAUSED BY SCEEROTIUM ORYZAE CATT. 
In the rice fields at Crowley, La., in the spring of 1919, an abundance 
of small, black sclerotia were found in the tissues and on the surface of 
old rice plants and stubble of the previous year. The same condition 
was noted again in the spring of 1920, at which time the organism was 
obtained in pure culture from the sclerotia. The fungus was then thought 
to be of an entirely saprophytic nature. On August 5, 1920, considerable 
lodging was noted in a field of Early Prolific rice which was being har¬ 
vested near Crowley. The affected plants were more or less collapsed, 
and the panicles were generally poorly filled and light. Near the ground, 
two or three nodes from the base, the stems appeared darker, and the 
internode where the irrigation water stood was found to be almost com¬ 
pletely destroyed (PI. 125). Only the thin epidermal layer remained 
intact, and the stem often was completely collapsed at this point. In 
the cavity of the diseased portion of the stem and in the diseased tissues 
1 Reinking, Otto A. Philippine economic-plant diseases. In Philippine Jour. Sci. Sect. A, v. 13, 
no. 5, p. 228. 1918. 
