Bean Anthracnose 143 



of inoculum for the infection of bean seedlings. Apparently soil that is 

 devoid of affected bean tissue cannot serve as a source of inoculum for 

 more than two or three months, or is not an important factor in bringing 

 about infection even though a few spores may live over winter in it. 



In order to determine whether old affected vines and pods can serve 

 as a source of inoculum under conditions prevailing out of doors at planting 

 time in the spring, Davis White Wax beans were planted on June 10, 1916, 

 in clean soil in the disease garden; that is to say, in soil in which beans 

 had not been grown since 1911, at which time they were badly affected with 

 anthracnose. Four rows, with forty hills to a row and five seeds to a hill, 

 were planted in the following manner and with the following results 

 (recorded June 26): 



Row 1. Seed spotted with anthracnose planted. No mulch used. 

 Only fifteen plants in six hills were alive, all of which showed affection 

 with anthracnose. 



Row 2. Clean seed planted, and hills mulched by placing over each 

 a handful of old affected vines left outdoors in a pile over winter. One 

 hundred and sixty-five plants appeared, every one affected on stem or 

 leaves or both. 



Row 3. Clean seed planted, and hills mulched by placing over each 

 a handful of old affected vines kept dry in seed house. One hundred and 

 seventy-one plants appeared, every one affected on stem or leaves or both. 



Row 4. Clean seed planted. No mulch used. This row was about 

 a rod north of the others. One hundred and sixty-nine plants appeared, 

 on which no infection was observed at this time. 



The weather from June 10 to June 15 was clear and warm most of the 

 time and was favorable for seed germination. From the evening of June 

 15 to June 21 inclusive it was cool and rainy or cloudy, weather very 

 favorable for infection to take place. From June 22 to June 26 inclusive 

 it was clear and warm. 



These results plainly indicate that under favorable conditions in the 

 field, affected bean pods and vines from the crop of two preceding years 

 can serve as a source of inoculum when they come into contact with 

 seedlings of a susceptible variety of beans. Nevertheless it is probable that 

 but little infection takes place from Contaminated soil or from overwintered 

 vines that are plowed under in preparing the land. In these experiments 

 special pains were taken to place a considerable amount of badly affected 



