Insect and Disease Control 271 



Course of development. 



As described by Smith ^ and his associates in referring 

 to a serious outbreak of this disease : " The trouble con- 

 sisted in the dying of the buds on the fruiting wood, spotting 

 of the green twigs, and dropping or non-development of 

 the young leaves and fruit. Particularly noticeable, and 

 the most prominent feature of the disease, was a copious 

 'gumming' or exudation of masses of gelatinous sap from 

 the twigs, originating in the dead spots and buds. This 

 gumming was extremely abundant in wet weather all over 

 the one-year-old fruiting twigs of affected trees, and with 

 the blighted leaves and fruit and spotted, leafless, dead or 

 dying twigs and shoots, gave the tree a most distressing 

 and alarming appearance. The crop was entirely ruined 

 in badly affected orchards and the trees brought into an 

 extremely weakened condition." 



Under California conditions, particularly in the valleys 

 where this disease has at times prevailed to a serious extent, 

 most of the infection takes place during the winter. Twigs 

 that appeared healthy in December may show definite 

 infection by the first of February. 



Methods of control of blight 



Experience has demonstrated that this disease can be 

 completely controlled by spraying with bordeaux mixture. 

 A single thorough application made any time during the 

 period from about the first of November to the middle of 

 December appears to be effective. If the application is 

 delayed until later than December, it is correspondingly 

 less effective. Applications later than the first of February 

 have little or no controlling effect on the disease, 

 i Cal. Expt. Sta. BuU. 191. 



