

DISEASES OF TRUCK CROPS. 35 



(string or snap bean, Phaseolus vulgaris L.) throughout our terri- 

 tory. Onty a few specimens were collected, since the bulk of our 

 field work was done after most of the crop had been harvested. Rec- 

 ords from pickings in one garden (Golden wax) in Austin were 

 obtained with the following result : Picking May 17, no anthracnose ; 

 May 21, 4.35 per cent ; May 26, 100 per cent. 



The rapid increase between May 21 and 26 was favored by an 

 abundance of rain. 



In some localities the Kentucky Wonder, a climbing variety with 

 green pods, is seriously affected. The foliage is little affected by this 

 disease, but bacterial blight is often present and may be erroneously 

 diagnosed as anthracnose. 



Specimens collected : Austin ; San Antonio, 1395 ; Llano, 1764. 



Stem anthracnose (Colletotrichum caidicolum Heald and Wolf, 

 32). — A destructive disease of the Kentucky Wonder bean, observed 

 in a single locality, was found to be due to this fungus. A super- 

 ficial examination of the affected field showed a considerable number 

 of plants which were completely dead, others were dying, while still 

 others that were less affected exhibited more or less chlorosis of the 

 foliage. An examination of the root system showed it to be in normal 

 condition, while the only deviation from normal in the foliage was 

 the marked chlorosis. 



An examination of the stems showed that brown, depressed cankers 

 were present an inch or more above the ground level. The cankers 

 were longitudinally elongated (20 to 40 mm.), more or less irregu- 

 lar, rough and frequently somewhat fissured or open. On the chlo- 

 rotic plants the canker occupied one side of the stem, on the plants 

 that were dying the stem was nearly girdled, and on all dead plants 

 examined the canker had completely encircled the stem. (PL VI, 



fig. 8.) 



Acervuli do not occur on the young cankers, but nearly mature 

 or complete cankers show a few which are visible to the naked eye 

 as small black specks (PI. VI, fig. 8 (a), while they become much 

 more abundant on the stems of plants which have been dead for a 

 few days. 



Acervuli scattered, black when mature, low convex, 150 to 250 fi in 

 diameter (PL VI, fig. 6) ; setae abundant, brown, septate, blunt 

 pointed or sometimes tapering, 60 to 120 by 3.5 to 4 /z ; conidiophores 

 nearly half the length of the setae, cylindrical, hyaline, generally 

 one or two septate; spores falcate, hyaline, granular, and 18 to 30 

 by 3.5 to 4 ^. (PL VI, fig. T.) 



Two species of Colletotrichum have previously been reported as 

 occurring on Phaseolus species. Colletotrichum lindemuthianum 

 (Sacc. and Magnus) Briosi and Cav. is the cause of the common 



226 



