254 



THE CANADIAN HORTICULTURIST 



November, 191 1 



southern nurseries and secure just as 

 good results from them as from stock 

 from the home nursery. 



DISADVANTAGES 



Some of the disadvantages of growing 

 nursery stock at home and in colder dis- 

 tricts include the following : There is a 

 temptation at home to grow nursery 

 stock in rather rich soil in order to get 

 a strong growth and a strong tree. If 

 you plant your trees on a clay soil or a 

 heavy soil there will come certain years 

 when the fall is favorable to late growth 

 when you will lose a large proportion 

 of fine, hardy varieties such as Mcin- 

 tosh Red and Fameuse. So if one wants 

 to have home-grown stock one must 

 grow it on soil which is not too rich. 

 If your soil is well drained and warm 

 your stock should be thoroughly ripen- 

 ed before the winter sets in. 



Another disadvantage of growing 

 trees at home is that one loses one year 

 very often in the growth of trees if one 

 wants to get good stock, because no mat- 

 ter whether you grow your trees on light 



soil or heavy soil, we have found in 

 some winters in a cold climate the trees 

 become what is known as "black heart- 

 ed." This is due to the fact that the 

 trees have made too late a growth, not- 

 withstanding the greatest care. It may 

 be also that trees have ripened their 

 wood all right and a very severe winter 

 follows while the trees are quite young, 

 and the result is the pith and wood of 

 the trees are damaged, but the cambium 

 being alive the tree goes on growing 

 next year, and unless one treats the tree 

 the way I have described one is liable to 

 have black-hearted trees. While black- 

 heart may not be a very serious injury 

 to a tree in its early history, just as 

 soon as they begin to lose the branches 

 disease will begin to work on the trees, 

 and eventually the tree will decay and 

 break down. After a very severe win- 

 ter, we have found that black heart oc- 

 curs in trees set out in the orchard three 

 or four years. As a rule, I think I am 

 safe in saying it occurs in the nursery. 

 We want to avoid this black heart in 

 trees. 



The Silver Leaf Disease of Fruit Trees 



Dr. H. T. Gussow, Dominion Botanist, Ottawa 



I desire to make an appeal to the fruit 

 growers of Canada for cooperation in 

 preventing the spreading of this alarm- 

 ing disease, the "Silver Leaf" of fruit 

 trees. Already this disease has been lo- 

 cated in several provinces. 



As the name indicates, this disease 

 may be recognized by a silvery or milky 

 gloss on the upper surface of the leaves 

 of apples, plums, peaches, cherries, cur- 

 rants and gooseberries. In Canada 

 authentic cases have occurred only on 

 apples and plums, but in Europe this 

 disease has often been found in the other 

 kinds of fruits. It is somewhat difficult 

 to recognize the silvery appearance of 

 the leaves, which, however, may become 

 so pronounced as to completely whiten 

 with a kind of bluish white tinge, the 

 foliage of one or more limbs, or often 

 the whole tree. 



The use of sprays like Bordeaux or 

 lime-sulphur results in the covering ot 

 the leaves with a bluish or yellowish 

 white film. This may give the tree an 

 appearance not unlike "silver leaf" but 

 on wiping the leaves, this covering is of 

 course easily removed, while in the real 

 "Silver Leaf" the color will remain. 

 Hence, it is important to distinguish 

 carefully between these two facts. In 

 ()rder to be sure of the disease specimens 

 will gladly be examined and reported 

 upon by the Division of Botany, Central 

 Experimental Farm, Ottawa. 



Growers should try to become familiar 

 with the appearance of this disease which 

 is by no means a new trouble in this 

 country, but which has unfortunately es- 



caped detection until the discovery of 

 undoubted cases of "Silver Leaf" in 



Silver Leaf Disease in Apples 



The top branch shows the silvery appearance 

 of leaves when compared with the healthy twig 

 below. The twiss towards the right show the 

 fructification of the oasual fungus. 



Nova Scotia, a few months after I took 

 up my duties there. No doubt every 

 reader is familiar with the silvery foliage 

 of some of our native willows and pop- 

 lars. From a distance these trees may 

 be easily recognized on account of the 

 bluish white appearance of their foliage. 

 If you bear in mind the appearance of 

 this color when examining your orchards 

 if you find that it is not due to any milky 

 film of sprays, there exists the probabili- 

 ty of the presence of this "Silver Leaf" 

 disease. I again solicit samples of fol- 

 iage, for we cannot be too careful in tak- 

 ing every possible step to prevent this 

 disease from becoming a source of real 

 danger to one of the country's most im- 

 portant industries. 



NATtTRB OP THE DISEASE 



The "Silver Leaf" is injurious to the 

 life of the trees that have been enumer- 

 ated. The trees maj' at first show only 

 one limb affected, gradually another falls 

 a victim, until the whole tree becomes 

 involved. The disease works slowly, and 

 it may take from three to five years be- 

 fore the disease has involved a whole 

 tree. This depends naturally upon the 

 size of the tree. During the first few 

 years the affected branches bear some 

 fruit, but bearing soon becomes a thing 

 of the past and the tree dies limb after 

 limb. It may be said that a tree once 

 attacked nearly always dies. It is our 

 experience that it bears little or no fruit 

 previous. Protection practically amounts 

 to immediate destruction of the trees 

 which show this disease. 



WARNING TO GROWERS 



The "Silver Leaf" disease has been 

 recorded and has been personally ob- 

 served in the following provinces : On- 

 tario (Ottawa only). Nova Scotia (sever- 

 al records). New Brunswick, British 

 Columbia, and in the experimental or- 

 chards in Manitoba. No case has yet 

 been received from Quebec, the Niagara 

 district, or from any of the other 

 provinces where fruit is grown. This 

 must not be taken as an indication of 

 its non-existence. I have reason to be- 

 lieve that the disease is very widely 

 spread. The disease is very serious. 

 Growers in this country are advised to 

 examine their trees very carefully and 

 give the disease no chance of establish- 

 ing itself firmly all over the country. The 

 fruit industry is in real danger. With- 

 out wishing to be an alarmist we cannot 

 afford to neglect the lessons taught us 

 by this disease in other countries, and 

 every fruit grower should unite with tho 

 government in the efforts which are be- 

 ing made to arrest and control the spread 

 of "Silver Leaf." 



Stereum purpureum, the fungus which 

 causes "Silver Leaf,' is a wound para- 

 site. The fungus is liable to gain en- 

 trance through any wound in the bark 

 or root. It produces its fructification or» 



