i g6 THE FRUIT GROWER'S GUIDE. 



50 at night, 55 by day, and 65 from sun heat, it being better to enhance the growth 

 of the foliage aiul fruit by a comparatively high temperature from sun heat than to 

 increase the artificial heat until the stoning is completed. When the plums have stoned 

 the temperature may be gradually raised to 60 at night, 65 on dull days, and 70 to 

 75 from sun heat, with a free circulation of air from 05. After the fruit is ripe 

 gradually lower the temperature, admit air freely, yet maintain a minimum of 50. 

 Trees in pots answer well for very early forcing, but the same trees should not be forced 

 year after year as it is an exhausting process. 



DISEASES AND ENEMIES. 



Diseases. Numerous fungi infest plums, but few do much injury to any part of the 

 tree, except in seasons and localities favourable to their growth. 



Bladder Plums. These are marked by the abnormal size of the young fruits, their 

 pointed elongated form, greyish bloom or coat on the surface and by their being hollow 

 (bladder like). This* condition is produced by a fungus named Exoascus pruni, the 

 mycelium of which lives all the year round in the twigs, and from these it extends into 

 the flowers, spreads through and lies immediately below the skin of the ovaries, through 

 which the stalk-cells burst and stand erect. Each long cell is an ascus, containing eight 

 globular spores, which are set free about the time the affected fruits turn a dirty yellow 

 colour and wither. The spores are scattered by the wind and, failing on young twigs, 

 reproduce the fungus under favourable conditions. Twigs showing traces of the disease 

 and the infested fruits should be cut oft and burned. 



Gum. Winter and spring pruning have a tendency to induce exudation from Ihe 

 wounds and chronic gumming frequently follows, for which there is no cure but the 

 removal of the branch or tree. Gummosis, however, is sometimes common and fatal in 

 orchard trees. Cutting out the affected parts and dressing the wounds with an anti-fun- 

 gal and wet-excluding composition is the only available remedy. (See " Gum," Vol. I., 

 page 234.) Inducements to gumming too rich soil, overfeeding, low sites, loose deep 

 soils, and stagnant water at the roots ; these, with everything tending to exuberance, 

 late growth, and immature wood, must be avoided. Thorough drainage, good firm soil, 

 careful planting, judicious pruning and skilful management all round are the best means 

 of preventing gum. 



Mildew. The flowers and young leaves of plum trees are sometimes thinly coaled 

 with whitish powder, composed of the filaments and conidia of an early stage (Oulium) 



