108 Diseases of Economic Plants 



This disease has been especially destructive in Colorado. 

 Three applications of Bordeaux mixture, 3-2-50, with 2 

 pounds of rosin-fish-oil-soap as an adhesive, applied: 

 (1) when the canes were 8-12 in. high; (2) two weeks later; 

 (3) two weeks later, gave excellent results in Colorado. 



Yellows. ^'^^ — Affected plants are stunted, yellowish, and 

 recall peach yellows. Laterals are dwarfed, leaves are small, 

 curled downward at the margins, and yellow-mottled. 

 Berries dry up without ripening or are insipid when mature. 

 Health and disease may occur upon the same plant. The 

 cane itself and roots appear normal. The disease appears to 

 be limited to raspberries and has been recorded in many 

 states from Massachusetts to California. 



The cause and remedy are not yet known. Diseased plants 

 should be burned and resistant varieties planted. 



Gray-mold (Botrytis) , and Blue-mold {Penicillmm) . — 

 These molds cause decay of fruit in transit. Care to avoid 

 wounds and over-ripeness, also prompt cooling and ventila- 

 tion, are necessary. 



Double-blossom * ^^^ {Fusarium riibi Wint.). — Double- 

 blossom occurs on dewberry and, to some extent, on the 

 high-bush blackberry. It is most abundant on the Lucretias, 

 but is also a serious pest on the Rathbone. The disease 

 makes its appearance in the spring, just as the leaf buds are 

 opening, although it can be detected previous to that time 

 by the enlargement of the diseased buds. 



Instead of the normal shoots and leaves a witches' broom 

 is produced; the entire bud l)eing involved or only a part, 

 according to the attack. When the flower buds open, they 

 show a great variety of deformities: sometimes only slightly 

 distorted; sometimes with increased number of stamens and 

 petals and with enlarged, thickened petals and sepals. Even 

 those flowers which appear most nearly perfect have dis- 

 eased ovaries, and the fruits from these brooms are always 

 worthless. 



Double-blossom usually appears during the second harvest 

 * Prepared by M. T. Cook. 



