304 



The Canadian Horticulturist. 



some places, is exceedingly troublesome to 

 grape-growers. It is really a form of the 

 downy mildew of the grape-vine, which 

 first appears on the leaves, and is called by 

 the former name when it attacks the fruit 

 itself. You should gather and burn all 

 specimens afiected, so as to prevent the 

 spread of this fungus, and next season begin 

 early to spray with the Bordeaux mixture, 

 or with the ammoniacal sulphate of copper, 

 both of which are elsewhere formulated. 



For a more particular description of the 

 brown rot, see Vol. 12 of this journal, page 

 297. 



GRAPES IN MUSKOKA. 



84. Sir, — Can grapes be successfully 

 grown in Muskoka, and, if so, what varie- 

 ties ?— T. B. 



Will some Muskoka correspondent please 

 answer .-' 



THE WALNUT TUSSOCK MOTH. 



86. Sir, — I enclose you a specimen of a 

 worm that is infesting the walnut trees in 

 this vicinity, and, if not checked, will com- 

 pletely defoliate them. The trees are so 

 high that it is difficult to reach them with a 

 spraying pump. — W., Grimsby. 



Reply by Mr. Jas. Fletcher, Experimental Farm, 

 Ottawa : 



The caterpillar on the black walnut is 



Halisidota CarycB, the Walnut Tussock 



Moth, sometimes very common on walnuts, 



butternuts, hickories, elms and many other 



trees. Of course Paris green will kill them 



if you can apply it ; but this seems to be 



your difficulty. By fastening your nozzle 



to the end of a light rubber tube, and then 



attaching this to a long bamboo, you can 



raise it a considerable height . You probably 



know of this method as figured by Dr. 



Riley. In this way a spray can be thrown 



over almost any apple tree I have required 



to treat. 



WOOD ASHES ON CLAY SOIL. 



87. Sir, — Would you recommend unleach- 

 ed ashes for small fruits or clay soil, or 

 would leached ashes be better ? — A Sub- 

 scriber, Newton. 



As a rule, it is not wise to apply unleached 

 wood ashes to stiff clay soils. The chief 



objection is the mechanical effect produced 

 by the potash, for it renders such soil more 

 tenacious and lumpy than before ; farther 

 than this, it is less needed upon such soil as 

 manure, because there is usually present a 

 larger amount of potash in composition than 

 there is in lighter soil. 



Leached ashes, on the other hand, consti- 

 tute a very valuable fertilizer on clay land, 

 for they consist largely on carbonate of lime, 

 which is itself valuable as a fertilizer, and 

 has a beneficial effect upon heavy soil, in the 

 first place promoting nitrification, and in the 

 second place, rendering the soil looser and 

 less liable to puddle. 



BLACK KNOT. 



88. Sir,— Is black knot hereditary or is it 

 spread only by contact, and would it be safe 

 to plant a young plum orchard on the ground 

 of an old one which died a few years ago of 

 that disease ? — A Subscriber. 



No, the black knot is not hereditary, neither 

 is it spread by contact, therefore we see no 

 reason, under this head, why a new orchard 

 should not be planted on the same ground as 

 the old one. The black knot is a fungus 

 which is propagated by very tiny spores. 

 These, though they correspond to seeds in 

 higher plants, are organized upon a lower 

 scale, and grow by cell divisions. Fungi do 

 not have leaves, stems and roots, with all 

 their separate functions the same as plants o* 

 a higher order ; they have, however, a por- 

 tion which corresponds to the root, called 

 Mycelium, which enters in between the cells 

 of the plum wood and draws its subsistence 

 therefrom. The plum knot fungus has also 

 a portion which corresponds with the 

 branches of plants, little thread-like portions 

 called Conidia, and upon these are borne the 

 tiny spores above referred to. It is by these 

 that the disease is propagated. They are so 

 tiny that they float about from place to 

 place in the air, and, lodging upon the 

 wood of the plum or cherry trees, immedi- 

 ately proceed to grow. By this will be seen 

 the great importance of carefully destroying 

 all trees in the neighborhood that are badly 

 affected with the knot, and of always care- 

 fully cutting out every knot upon its first 



