THE BRAZILIAN DISEASE OF MANIHOT. 



28l 



73-13 P 61 " cent f starch in the dry material as in the normal mandioca, there was scarcely 63.90 

 per cent in the diseased mandioca. The observations show that the disease attacks very often the 

 cuttings (mudas) of mandioca, when they are made very long before planting. In this case the 

 tips of the stems begin to rot. As the circulation of the sap occurs even in the cut stems, the conta- 

 gion propagates itself in the bundles 

 (canaes) without leaving external 

 signs. The slips cut from such 

 stems die for the greater part, and 

 on the other hand, are liable to con- 

 taminate others. 



The disease is grave, contagious, 

 easily propagated, inoculable, and 

 can be transmitted by insects. If 

 care is not taken it may cause con- 

 siderable injury to the cultivation 

 of this plant of ours, which is of 

 general use. 



With some cultural precautions 

 the malady may be avoided or les- 

 sened in severity. 



Curative treatment can not be 

 applied, since the disease is internal, 

 and generalizes itself directly in the 

 plant. 



The preventive measures which 

 we advise, in order to avoid the pro- 

 pagation of the plague, are as follows : 



1. Plant resting shoots (mudas) 

 absolutely not suspected, coming 

 from healthy plantations, rejecting 

 all doubtful stalks. 



2. Cut the cuttings (estacas) 

 with the greatest care, without tear- 

 ing or wounding the tissue, in such a 



manner as to reduce the surface and Fig. 138.* 



the possibility of contamination. 



3. Do not plant the mandioca in soil infected by preceding diseased plantings, but cultivate 

 other things not subject to contamination by the same bacteria. 



4. Plant the cuttings as soon as possible, in order to avoid the contamination which occurs 

 easily during the period of slow growth. 



5. Plant resistant varieties: Mandioca parda and Mandioca azul resist better than the Mandioca 

 branca and at pirn. 



The bacteria are found in pure colonies under the bark, in the young swellings. The isolation 

 of the microbe, likewise the artificial inoculation of the plant, show, fortunately, that there are 

 present no other bacterial diseases. 



A more extensive account of this disease was prepared, but its publication has been 

 delayed. 



LITERATURE. 



1912. BONDAR, GRBGORIO. Uma nova molestia bacteriana das hastes da mandioca. 

 No. 4, April 1912, pp. 15-18, 3 figures. Brazil. 



Chacaras e Quintaes. vol. v. 



*Pic. 138. Stem of manihot attacked by bacterial disease, a. Bacterial blisters and exudatc. b. Cross-section 

 of stem showing location of the diseased part (at the top), c. Bacillus manihotus A. Berthet, from a diseased manihot 

 plant. X 1,000. (After Bondar.) 



[The photographs and drawings in this volume, as in Volumes I and II, were made, with a few exceptions, by James 

 F. Brewer. The writer, however, selected the parts to be drawn, or photographed, and finally checked up under the 

 microscope nearly or quite all of the drawings. With exception of figs. I and 2 of plate 1 1, the colored figures were 

 also made by Mr. Brewer. The color chart, referred to in various places as " Ridgway, " is the first edition of Robert 

 Ridgway's Nomenclature of Colors for Naturalists.) 



