SNAILS AS PREDISPOSING AGENTS OF SUGAR CANE 
“ROOT DISEASE” IN LOUISIANA 1 
By R. D. RANDS 
Pathologist, Office of Sugar-Plant Investigations, Bureau of Plant Industry, 
United States Department of Agriculture 2 
Root disease, or rootrot, has been considered a major factor in the gradually 
declining yields of sugar cane in Louisiana. The losses, particularly in “ stubble, ” 
or ratoon crops, have lately attained such proportions as to render of questionable 
value the practice of growing even one year stubble. Although root troubles 
have in the past received but little scientific attention in Louisiana, rootrot in 
other countries has usually been ascribed to various fungi. 
Close study of a large number of incipient cases in the principal sugar sections 
of Louisiana has revealed that a small snail ( Zonitoides arboreus, Say) 3 may 
be primarily responsible for the trouble. So far as known to the writer, snail 
Injury has not hitherto been reported anywhere on sugar cane. The damage, 
which is most extensive on the soft, white, terminal portion of the root, consists 
typically of minute cavities or pits 0.3-2.0 mm. deep and of similar diameter, 
resulting frequently in direct death of the growing point, and the development 
of secondary rootlets farther back. The latter, in turn, may be attacked, giving 
the roots a fibrous, bunchy appearance. On the older portions of the root the 
pits extend only to the hard central bundle sheath. No injury to the rhizome, 
or underground stalk, has been observed. Around the pits and abrasions lesions 
commonly develop, due to invasion of the weakened tissues by soil inhabiting 
microorganisms. The extension of these combined with further snail injury grad¬ 
ually brings about the final death of the root. In advanced cases most of the 
older, deeper roots have died forcing successive development of new ones nearer 
the surface of the soil. While root lesions apparently not connected with snail 
damage have been observed, most of the root deterioration seems to be directly 
proportional to the extent of such injury. 
That the above-mentioned species of snail is responsible for the root pitting 
has been repeatedly confirmed both by direct field observations and by feeding 
tests with isolated snails in the laboratory. As many as 150 individual snails 
have been counted in casual examination of the soil about the roots of a single 
backward plant in a poorly drained field. They commonly occur in the earthworm 
1 Received for publication July 28, 1924—issued Nov., 1924. 
2 Grateful acknowledgments are made to Messrs. D. W. Pipes, C. C. Krumbhaar, and Elliott Jones, 
managers of Southdown Plantation, Houma, La., for furnishing laboratory facilities and asistance in this 
investigation. 
3 The writer is indebted to Dr. Paul Bartsch, Curator of Mollusks, U. S. National Museum, Washing¬ 
ton, D. C., for giving the following information: 
“This mollusk is known as Zonitoides arbor eus (Say). It has been reported from all the States of our 
Union, also from Canada as far north as Great Slave Lake. We have likewise had it reported from certain 
of the West Indian Islands. Normally, it makes its home under the dead bark of fallen trees and old 
rubbish heaps, squeezing into small crevices. 
“Sugar cane, as I recall it, has quite a lot of small roots about its base, and drooping dead leaves hanging 
about the stalks, a condition not unlike a rubbish pile. It is, therefore, not surprising that we should find 
the organism in question in such locations. It may fall from these roots onto the soil or get down farther 
in the burrows of other animals.” 
Journal of Agricultural Research, 
Washington, D. C. 
( 969 ) 
Vol. XXVIII, No. 9 
May 31, 1924 
Key No. G-369 
