338 STATE HORTICULTURAL SOCIETY 



some of our best varieties are very subject to the disease, he should make 

 use of the sprajiug mixtures who attempts to grow them. 



CROWN GALL. 



Many of the peach trees that have been brought into Michigan from 

 Ohio and Maryland have shown upon their roots swellings of various 

 sizes to which the name of '' Crown Gall," has been given. These are 

 most commonly found at or near the collar of the trees, but detached 

 swellings have often been found upon the smaller roots. When upon 

 large roots, or at the collar, the tree will be of little value and should 

 never be planted, as, even if it lives, the growth will be unsatisfactory. 

 The real nature of this trouble is not understood, but, even though it has 

 not been definitely shown to be contagious, the trees should be regarded 

 with suspicion. The swellings most generally appear in the nursery, and 

 are most common when the trees have been grown in moist soil, espe- 

 cially if it contains a large amount of decaying organic matter. In case 

 a tree growing in the orchard has been destroyed with crown gall, it will 

 be safest to remove the soil and replace it with fresh materials before 

 planting another tree. While it cannot be regarded as absolutely sure, 

 it is possible that where there are but one or two small swellings, upon 

 the smaller roots, the tree can be saved by cutting off the roots as far 

 from the swellings as possible. 



Care should be taken both by nurserymen and orchardists, in planting 

 trees in wet soil, especially if the land contains a large amount of organic 

 matter. Instances have been known w'here the disease was very trouble- 

 some on soils heavily enriched with stable manure, or where large 

 amounts of saw-dust have been worked into the soil; also where raspberry 

 plantations have been removed. Similar " galls " have been found on the 

 apple, pear and plum, as well as on the raspberry and blackberry. An- 

 other form of gall, which appears as small nodules upon the roots, is due 

 to the work of the "eel" worms (nematodes), but these are quite distinct 

 both in their appearance and nature. 



BLACK KNOT. 



The swellings upon the branches of the plum and cherry trees, to which 

 the name of "Black Knot" has been given, have been found very de- 

 structive. While in some seasons the growth is but slow, in others they 

 develop rapidly and destroy entire orchards. The development of the 

 knots begins during May and June, when, upon the branches that are one 

 or two years old, a slight swelling will be noticed and the outer bark will 

 crack, showing the green layer beneath, which will soon take on a russet 

 appearance. Upon the surface an olive-green mould will soon appear, 

 which is due to the development of summer spores of the fungus. These 

 are borne about by the wind and serve to scatter the disease. The de- 

 veloi)ment of the spores continues and, by autumn, the surface will be of a 

 black color, covered with innumerable minute pimples, in which the win- 

 ter spores of the fungus will be developed. These will ripen in Febru- 

 ary and thus the disease will secure another start. The old " knots " are 

 dry and hard and each year extend both ways along the branches, until 

 they reach a considerable size. By carefully examining the trees during 

 the early summer, the " knots " can be detected in the early stages of 



