234 



It is rarely necessary to employ control measures against this dis- 

 ease. When necessary, either lime-sulfur or Bordeaux, made up accord- 

 ing to the 3-3-50 formula to avoid injury from stronger mixtures, will be 

 found satisfactory. 



Orange Rust 



Caused by Gymnoconia intcrstitialis (Schlecht) Lagerh. 



Orange rust, the most conspicuous and one of the most serious oi 

 the bramble diseases, is in Illinois especially a blackberry disease. It is 

 easily recognized by the striking orange color of the leaves of infected 

 plants in spring. 



In late April or early May small greenish-yellow spots appear on the 

 under surface of the leaves of infected plants, and within a few weeks 

 the leaf surface ruptures, exposing large patches of orange spores on the 

 lower surface. The disease is systemic, and persists within the plants 

 from year to year, dwarfing, deforming, and eventually killing them. All 

 sprouts from runners of diseased plants are infected. 



The history of bramble orange rust in Illinois dates back to 1850. 

 Its present known distribution on economic hosts is shown on Map 88. 

 It appears to be more common and more abundant southward, and is 

 rather rare in the northern third of the state. 



Control is to be had only by digging out and burning infected plants. 

 The disease pervades all parts of the plant, persisting there until the 

 plant dies. Infection may be prevented to some extent by planting re- 

 sistant varieties, such as Snyder, and by taking care to eradicate all wild 

 blackberries in the neighborhood. 



Crown-gall 

 Caused by Psciidomouas tiDiicfacnciis E. F. S. 



Crown-gall, while occurring on all the brambles, is in Illinois par- 

 ticularly destructive to red raspberries. Damage from this disease is 

 extremely serious and is said to be the most important of the factors 

 limiting raspberry production in the state at the present time. 



Its known occurrence is shown on Map 89. It has been found in 

 28 counties widely scattered over the state, but appears to be less common 

 southward. 



Plants in the nursery suffer most from it, and it is there that most 

 plants become infected. If the grower would avoid loss from this dis- 

 ease he must insist on plants absolutely free from infection. 



Bramble-streak 



The so-called bramble-streak is a disease aft'ecting only the black- 

 cap raspberry. In other states it is said to be extremely serious. . 



It was first found in Illinois by A. S. Colby near Peoria in 1922. 



