210 NEBRASKA STATE HORTICULTURAL SOCIETY 



The fruit itself does not escape this disease. On the apple it 

 causes a yellow wrinkled spot frequently containing openings similar 

 to those seen on the lower surface of the leaves. Fruit spots are 

 usually found at or near the blossom end. The disease gains entrance 

 through the calyx lobes while the fruit is quite young. 



The disease is disseminated from the corky galls found on cedar 

 trees commonly called cedar apples. These galls contain spores which 

 when the weather becomes warm and sufficient moisture is present, 

 multiply rapidly, causing the cedar apples tp throw out long, yellow, 

 jelly-like masses containing millions of spores, which are blown 

 away and scattered by the wind as soon as the mass becomes dry. It 

 is impossible to say how far these spores may be carried by the wind, 

 but few orchards are free from rust even when no cedar trees are 

 near. 



When these spores fall upon an apple leaf, infection is produced 

 if there is sufficient warmth and moisture. Serious epidemics do not 

 occur during extremely dry weather, for the reason that moisture is 

 necessary to the germination of the spores. Ordinarily, however, 

 there is suiTicient moisture for germination at the time when spores are 

 being disseminated, and after growth begins the disease continues, rain 

 or shine. 



The spots on the apple leaves produce spores, as before mentioned, 

 which in turn infest the cedar trees, producing new galls, from which 

 come the spores to infect the apple trees another season. 



The varieties of apples most susceptible to the disease are Wealthy, 

 Red June, Jonathan, Northern Spy, Rome Beauty, Iowa Blush, and 

 Missouri Pippin. Ben Davis, York Imperial. Gano. and Orimes Oolden 

 are only moderately susceptible. Varieties only slightly susceptible or 

 immune are Winesap, Arkansas, Northwestern Greening, Oldenburg, 

 Ralls Genet, Staymen Winesap, Maiden's Blush, Sweet June, Yellow 

 transparent, and Cooper's Early. 



Susceptibility of different varieties varies with climatic conditions 

 and often with individual trees. 



Several experiments have been conducted for the purpose of deter- 

 mining the best methods of control for cedar rust. Dr. R. A. Emerson, 

 of the Nebraska Station, found that if the apple trees are sprayed 

 thoroughly with bordeaux mixture of the regular 3-4-5 formula, just 

 as soon as the cedar apples have begun to enlarge, becomes gelatinous 

 and orange colored, the disease may be largely prevented. This 

 depends largely upon weather conditions and varies with the season. 



The Virginia Experiment Station recommends spraying with either 

 bordeaux mixture or lime-sulphur or the destruction of the cedar trees 

 for the control of cedar rust. 



The only safe and sure remedy for the disease is the destruction 

 of the cedar trees in the localities where the cedar rust is most trouble- 

 some and where the removal of the trees can be accomplished without 

 difficulty it is the best method to follow, but in some parts of this 



