PLUMS AND DAMSONSDISEASES AND ENEMIES- 



"97 



of a fungus named Podospheera tridactyla, and occasionally also by Podosphsera oxy- 

 acanthee. It is the Oidium or mildew stage of these fungi which proves hurtful to the 

 fruit setting, and cripples the young growths. The best remedy is to dust the affected 

 parts with flowers of sulphur, or syringe them with potassium sulphide, \ ounce to a 

 gallon of water. (See " Mildew," Vol. L, page 245.) 



Orange Fungus. This parasite produces thickened, fleshy, orange-red spots, of 

 irregularly rounded outline, on the leaves, as shown in the upper figure of the illustra- 

 tion (Fig. 51). A section of the leaf (lower left-hand figure) passing through these 

 spots shows the flask-shaped spaces, 

 each containing eight oval spores, 

 which escape from the apex, as shown 

 enlarged, and, falling on a suitable 

 nidus, reproduce the fungus in the 

 summer. It is the mycelium of the 

 fungus (Polystigma rubrum) that take 

 nourishment from the leaves and cause 

 them to fall prematurely, sometimes 

 before the crop is perfected, when the 

 fruit shrivels, becomes discoloured, and 

 unwholesome. Spraying the trees with 

 a 1 per cent. Bordeaux mixture when 

 the leaves are fairly formed is the only 

 effectual preventive. It is recom- 

 mended to collect the diseased leaves, 

 also those which have fallen, and burn them. The ground should be dug early in 

 spring, before the young loaves appear, to prevent them being infested. 



Rot. One of the worst fungoid diseases in plums is caused by Oidium fructigena, 

 and is figured and described under "Apple Diseases," Vol. II., page 36. Happily its 

 attacks are not common in this country, but at times the diseased patches spread over 

 a large portion of the fruits and cause them to become almost entirely whitish yellow. 

 It is most prevalent while the fruit is ripening, but it has been noticed on half-grown 

 fruit. The tufts of yellowish white, however, do not usually appear until the fruits are 

 ripe or nearly so. The mycelium appears to have the property of causing the flesh to 

 shrivel and render the fruits unfit for use. There is no cure, and preventives have not 



Fig. 51. OBANOB Fuuous (POLYSTIOJU. ETJBEUM) ox PLUM. 



