EXPERIMENT STATION BULLETINS. 365 



tions of the presence of yellows. This may occur from one to six weeks earlier 

 than the normal period of maturing. Such fruits are also highly colored posses- 

 sing red spots and streaks which often extend from the surface to the pit, the 

 flesh being marbled and streaked with red. The buds formed during the sum- 

 mer, for growth the next season are also sometimes prematurely unfolded. But 

 the most characteristic feature is the growth of bunches of slender twiggy 

 branches during summer and autumn from the crotches and upon the older 

 branches. These wiry shoots bear narrow sickly leaves of a yellow color and 

 being produced in clusters give a characteristic appearance to affected trees. 



Trees which show these characters — premature ripening of fruit — fruit spotted 

 and blotched with red; twiggy, clustered shoots bearing small yellow foliage 

 may be considered as unmistakably affected with yellows and should be at once 

 condemned to the fire heap. Although the exact manner in which peach yellows 

 is naturally spread from diseased trees is not understood, it is known to be 

 contagious. Thus its appearance in one part of an orchard is almost certain 

 to be followed by other cases unless the first trees to show it are removed 

 without delay. Artificial infections may arise when buds from yellows-affected 

 trees are used in budding, hence this means of dissemination should be guarded 

 against by the use of buds from stock of unquestioned health. The spread of the 

 disease by the use of pits from yellows affected fruit is believed to be small 

 as such pits are not liable to germinate. 



Control of Yellous — Thus far the only successful measures employed in com- 

 bating the disease have been of a preventive nature. This consists of digging 

 or pulling out and burning every tree which shows the characteristic symptoms 

 of yellows and the more promptly this is done the better for the health of sur- 

 rounding trees. Fertilizer tests with a view to lessening or preventing the 

 spread of the disease have not been successful and the same may be said in 

 regard to the matter of spraying 



Peach Rosette is a disease of the peach in the southern states. Its effects on 

 the tree are similar to those of yellows and like that disease it is to be controlled 

 only by destruction of affected trees. 



LEAF CURL. 



(Exoascus deformans.) (Burk.) Fckl.) 



This disease affects the leaves of the peach causing great distortion. The 

 leaf becomes thickened, bent and twisted, sometimes only in part or the entire 

 blade may be affected, the fungus causing a blistered appearance very character- 

 istic of the disease. A similar appearance is sometimes caused on leaves of 

 peach, plum and cherry by the attacks of plant lice, but in this case the presence 

 of the lice will usually indicate the true cause of the curling of the leaves. 

 The trouble appears soon after the foliage is expanded causing the affected leaves 

 to fall off. In severe cases, the trees may be entirely stripped of their foliage 

 and normal growth seriously checked. Bearing trees lose their fruit for the 

 season and often fail to form fruit buds for the next. A new crop of leaves 

 generally appears after the falling of the first but the check is often so severe 

 as to prevent the proper maturing of the new wood in time to resist freezing. 



The fungous parasite lives through the winter in the form of mycelium in the 

 buds and twigs of affected branches and grows out with the new leaves in the 

 spring. It has been demonstrated, however, by recent investigations that most 

 of the early infections of the foliage arise not from this hybernating mycelium 

 but evidently from spores produced during the previous season. Thus it has been 

 found possible even by a single spraying to reduce the number of infections 

 90% — 98% which would not be the case if they arose from a perennial mycelium. 

 The spores are produced in minute cells which cover the surface of the deformed 

 leaves. The conditions which appear to favor the infection of healthy foliage are 

 a low temperature with abundant rainfall during the early part of the growing 

 season 



Treatment. — The fact that the mycelium of the fungus hibernates in the liv- 

 ing buds of the tree would seem to point to the uncertainty attending any 

 efforts to check the disease by spraying. But while spraying may not affect 

 the disease already present in the tree.it is very useful in preventing its spread 

 to healthy leaves and the consequent establishment of the fungus in the newly 

 forming buds. Hence in this case the use of fungicides is apt to show most 



