208 MANUAL OF FRUIT DISEASES 



Cause of anthracnose. 



This is a fungous disease, the cause of which is Pseudopeziza 

 Ribis. The fungus is carried through the winter by either the 

 conidial or the sexual stages and possibly as mycelium in the 

 canes. The infected leaves fall to the ground in the autumn, 

 and the fungus then penetrates all the tissues. Later it develops 

 an apothecium. In the spring ascopores ripen and are carried 

 to the new leaves, probably by the wind, although no observa- 

 tions have been made on this point. The time of inoculation 

 .is unknown, but severely infected plants have been seen on 

 June 8. It is known that about two weeks are required for 

 germination, penetration and the production of visible signs 

 of the disease, from which it may be reasoned that inoculation 

 occurs about the middle of May. The germtube within the 

 leaf, or other susceptible part of the plant, develops mycelium 

 which grows in localized areas and kills the tissues, resulting 

 in the formation of the lesions already described. The my- 

 celium finally forms a mat near the center of the spot where an 

 acervulus develops. At maturity this structure ruptures the 

 epidermis, liberating the conidia in gelatinous masses. These 

 spores are disseminated by rain and insects, but, on account of 

 their gelatinous character, probably are never carried by wind. 

 The conidia continue to propagate the pathogene throughout 

 the growing-season, thus accounting for the extent of the disease 

 in a local area. Conidia produced in late summer are capable 

 of living through the winter. Although, as previously stated, 

 mycelium in the canes may possibly tide the fungus over winter, 

 yet there is considerable evidence to the contrary. 



Control. 



It has been conclusively shown that bordeaux mixture 5-5- 

 50, or lime-sulfur solution 1-40 or 1-50, when applied at the 

 right tune, is effective in the control of anthracnose. It has 

 recently been found that dusting with the sulfur-lead mixture 

 (90 parts finely ground sulfur to 10 parts powdered lead ar- 



