490 INSECTS AFFECTING VEGETATION 



It causes the affected leaves to turn first yellowish in color, remain 

 erect in position, and finally to become bright red with an abun- 

 dant coating of the spores of the rust fungus. These spores are 

 readily scattered and may thus affect previously healthy plants. 

 The threads of the rust fungus (mycelium) live year after year in 

 the affected plants. For this reason the only remedy is to dig and 

 and burn all members of the rusted stools. (Ohio E. S. B. 121 and 

 79.) 



Crown Gall (See page 451). Leaf Spot (See page 491). 

 Cane Blight (See page 491). 



Double Blossom of Dewberry. The disease appears in the 

 earily spring and can be readily recognized when the leaf buds 

 open. The diseased buds are usually larger than the normal buds, 

 and frequently accompanied by one or more small buds which are 

 placed laterally to the main bud. When these diseased buds open, 

 a witches' broom is produced instead of the normal shoots. The 

 witches' broom may consist of a great mass of short, slender twigs, 

 or there may be one good but somewhat reduced shoot, together 

 with few to several of the short deformed shoots. The shoots of 

 these witches' brooms will frequently remain green after the old 

 canes are dead. The blossoms are usually deformed in varying de- 

 grees; having enlarged thickened sepals and petals, and sometimes 

 an increase in number of each, especially the latter. The deformed 

 petals are usually more or less wrinkled, giving the appearance of 

 being doubled. The stamens and ovaries are also subject to slight 

 modifications varying in degree and character with the severity 

 of the disease. 



The disease usually appears during the second year's harvest 

 and increases from season to season until the plants are worthless. 

 The disease does not vary in abundance from season to season ex- 

 cept to increase with each succeeding year until it becomes necessary 

 to destroy the plants. Very frequently old plants will have every 

 bud deformed. Diseased plants also show a tendency to produce 

 an abundance of late bloom which are usually smaller than the 

 normal blossoms but not otherwise modified. They frequently 

 bear the fungus and produce spores. (Del. E. S. B. 93.) 



However, the fact that the fungus does not penetrate beyond 

 the base of the bud makes it possible to control the disease by hand 

 picking of the diseased buds. This method has been tried and 

 found to be efficient and also much cheaper than any spraying 

 that is likely to be devised. The diseased parts should be picked 

 off as soon as the leaf buds open, when they can be readily detected 

 and easily removed. If the picking is delayed the growing foliage 

 will partially conceal many diseased buds and make the work 

 more difficult, require a longer time, and be less satisfactory. It 

 is practically impossible to remove all diseased buds some of 

 which may be only slightly affected and very small, but the re- 

 moval of each diseased bud means the removal of a source of in- 

 fection from which hundreds and even thousands of spores may be 

 distributed to the surrounding plants, If the picking is done at 



