1056 EXPERIMENT STATION RECORD. 



DISEASES OF PLANTS. 



A bacterial disease of sweet corn, F. 0. Stewart (New York 

 State Sta. Bui. 130, pp. 423-439, phi -/). — The author describes a disease 

 which has been under observation for the past three years and which 

 has caused considerable damage to sweet corn in the market gardens of 

 Long Island. Certain varieties seem to be more subject to the attack 

 than others, and losses of 20 to 40 per cent, and even of the entire crop, 

 are reported. The affected plants wilt and dry up without any appar- 

 ent cause, and this may take place at any stage daring their growth, 

 but is most liable to occur about the time of flowering. The leaves 

 first wilt and then gradually wither. The time which elapses between 

 the appearance of the disease and the death of the plant varies greatly. 

 Sometimes the plants recover, or may seem to recover for a time, and 

 later yield to the disease. Nothing abnormal appears about the roots 

 or subterranean portions of the stem except where the plants have 

 been dead for a considerable time. The most distinct character of the 

 disease is revealed when the stem is cut lengthwise, when the fibro- 

 vascular bundles appear as yellow streaks in the white parenchyma. 

 If the stein is cut crosswise and the cut surface exposed to the air for 

 a few moments a yellow, viscid substance exudes in drops. Examina- 

 tion of tbis substance revealed the presence of large numbers of bac- 

 teria, and it is to them that the disease is due. Pure cultures of the 

 germ are easily obtained, the organism growing readily at temperatures 

 of 21 to 28° 0. in neutral media of beef agar, potato agar, and gelatin. 



The organism is a short bacillus with rounded ends, usually occurring 

 in pairs, with a plain constriction between the members. No spores 

 have been observed, but old cultures have not been carefully examined 

 and the absence of spores can not be definitely stated. The organism is 

 motile, but not actively so. Its behavior on various culture media and 

 its chemical, temperature, and light reactions are described. 



The bacteria are always found in the vascular system, never occurring 

 in the parenchyma cells, and they injure the vitality of the plant by 

 plugging up the main water canals. 



The identity of the bacillus is not fully established, but it is consid- 

 ered specifically different from that causing the disease of corn known 

 as Burrill's disease, due to Bacillus cloaca}. 



Inoculation experiments are reported in which it appeared that the 

 soil or the seed may be sources of infection. Popcorn, field corn, oats, 

 and teosinte proved not susceptible to the disease when subjected to 

 soil and puncture inoculations. The author believes that the chief 

 method of dissemination of the germ is through diseased seed. Another 

 common way in which the germ is probably disseminated is by the use 

 of manure from animals fed on the diseased stalks. 



Soil treatments with lime and sulphur have proved of no benefit in 

 preventing this disease. As far as practicable the planting of non- 



