THE BRAZILIAN DISEASE OF MANIHOT. 



In 1912 Gregorio Bondar, of the Agronomical Institute at Campinas in Brazil, described 

 a disease of Manihot that appears to belong here. I translate from his Portuguese leaflet, 

 with some hesitation, as follows : 



The sweet mandioca (Manihot palmata), varieties white mandioca and aipim mandioca, has 

 been with us subject to a disease which apparently has not been met with in other countries. 



This rot of the stalks and the shoots (brotos) is caused by bacteria, Bacillus maniholus Arthaud- 

 Berthet. 



The disease was studied at the Agronomic Institute in Campinas by the [former] Director, 

 Dr. Arthaud-Berthet with our collaboration. The microbiological study was verified in the bac- 

 teriological laboratory by the specialist Dr. A. Perrier. 



In the Mandioca aipim the effects of the disease are as follows: The young shoots (br6tos) rot 

 internally, wither, and die. By the transparency of the bark one can perceive dark subcortical lines 

 which follow the bundles. Removing the bark one observes that these lines start from the sub- 

 terranean stalk, which becomes rotten in a line corresponding to the shoot (broto) or presents the 

 bundles (canaes) black, infected. In the young shoots (br6tos), the bundles (canaes) presently 

 decompose (fig. 138, b), injuring 

 the circulation of the sap and 

 causing the withering. The 

 disease may attack the shoot on 

 a single side, but presently gen- 

 eralizes itself in other bundles 

 (canaes). In young planta- 

 tions the disease occasions the 

 death of the plants. 



In the white Mandioca the 

 signs of the disease differ : The 

 shoots present subcortical swel- 

 lings which are produced in the 

 bundles by the coagulation of 

 the latex (fig. 138,0,6). These 

 swellings are elongate. The p; g \yj * 



subcortical accumulation 



breaks the bark and the gummy substance exudes, forming small superficial crusts, of a light yellow 

 color (amarello-clara) at the beginning, and afterwards reddish by oxidation. 



If the diseased shoots were (estiverem) grown on the stalks of the past year the black markings 

 of the disease run through even to the subterranean part without, however, forming gummy swellings. 



The roots do not manifest any signs of disease. In a planting of ten months we observed that 

 these roots were able to send out the shoots three or four times, which succumbed successively to 

 the bacteria, until the roots were completely exhausted, dying directly afterwards. 



We made numerous artificial inoculations of the disease. The healthy shoots, inoculated arti- 

 ficially with virus from the diseased plant, presented the same symptoms of disease after 1 5 or 20 

 days' incubation of the bacteria. 



The cuttings, infected with the bacteria before planting, died, rotting in the earth without 

 budding. Of 20 infected cuttings not a single one grew. 



The experimental work on the disease, as also many observations, were made in collaboration 

 with the Chefe de Culturas do Institute, Sr. Joao Herrman. 



Attacking old stalks, with the roots formed, the bacteria bring about exhaustion of the accumu- 

 lated starchy substance. 



The roots of the diseased stalks are unfit for food, for they are very hard, even when boiled two 

 or three times as long as the ordinary mandioca. 



The chemical composition varies greatly also. The anaylsis made by Sr. R. Bolliger, in the Agro- 

 nomic Institute in Campinas, revealed a noticeable diminution of the starchy substance: Instead of 



FiG. 137. Brazilian manihot wilting from bacterial disease. (After Bondar.) 

 280 



