PEACH DISEASES 



313 



the effect induced by the San Jose scale (Fig. 82)" ? At first 

 the spots are small and purplish red. As the diseased portion 

 enlarges, a light-colored area develops in the center (Fig. 82). 

 Later the spots are brown and confluent. In extreme cases 

 the fruit becomes cracked and a flow of gum follows.^ 



Cause. 



The lesions described above are induced by the fungus 

 Coryneum Beijerinckii.^The chief period of infection appears 

 to be from December to February; most inoculations occur 

 about January 

 first. In Cali- 

 fornia no in- 

 .fections occur 

 after the end of 

 April ; in Ore- 

 gon these take 

 place from May 

 10 to June 15. 

 Rainy, weather 

 favors infection: ' 

 The conidia of the fungus .are carried to the buds, leaves and 

 fruits, germination occurring in a short time in the presence 

 of moisture. After infection, spore-cushions break through 

 the skin of the various parts affected. These are visible to 

 the naked eye as dark spots, and are most abundant about 

 leaf scars and roughened portions of the bark on defoliated 

 twigs in the spring and summer. They also develop on leaf- 

 spots. The conidia appear to live through the summer lodged 

 in the bud-scales, being very resistant to desiccation. 



Control. 



' It has been found in the Pacific Coast regions that Coryneum- 

 blight can be controlled by fall and spring spraying. Peaches 

 should be sprayed about November first, just as soon as possi- 

 ble after the fruit is harvested. Bordeaux mixture 6-6-50 is 



FIG. 82. Coryneum-blight lesions on peaches. 



