Fungous Diseases of Ontario Orchards: Peach Yellows' 



M. B. Waite, Pathologist in Charge, Investigations of Diseases of Fruits, U. S. Department of Agriculture 



THE cause of the peach yellows is un- 

 known but it behaves precisely like 

 a parasitic disease. It is conta- 

 gious, spreads through the orchard from 

 colonies or from individual trees which 

 become centers of infection and is distri- 

 buted from tree to tree and orchard to 

 orchard by natural methods unknown to 

 investigators. In all respects, therefore, 

 it acts like a parasitic contagious disease. 

 Up to the present time, all microscopic 

 and bacteriological methods of investiga- 



tree gradually dies from the top down, 

 ordinarily becoming totally dead at four 

 or five years from the appearance of the 

 first visible symptom. 



The leaves on trees affected by this 

 disease usually turn yellow rather 

 promptly. This results in the common 

 name of the malady. However, fre- 

 quently when the trees are first attacked 

 and the fruit decidedly red spotted and 

 premature, on the whole tree or on cer- 

 tain branches, the leaves, instead of yel- 



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V bei 



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Hon have failed to reveal any parasites. 

 Investigations along these lines have 

 been wholly negative although they have 

 en pursued with great persistence and 

 oroughness. It seems almost certain 

 hat had it been an ordinary germ or 

 acillus, the methods employed would 

 have revealed the same. It is hard for 

 me to believe that the disease is not a 

 parasitic disease, however, and that some 

 day the parasitic organism will be found. 

 The failure to find the cause of the dis- 

 ease or any definite parasite associated 

 with it puts this discussion of peach yel- 

 lows on a different plane from that of 

 the ordinary fungous or bacterial diseases 

 of plants. However, by comparison with 

 definitely known germ diseases, such as 

 pear blight, and with a general know- 

 ledge of physiology and pathology, we 

 may be able to steer clear of false 

 theories and make the most of the facts 

 available. 



SYMPTOMS OF YELLOWS 



The most reliable symptoms of peach 

 yellows is the prematuring and red spot- 

 ting of the fruit. Another symptom al- 

 most equally certain is the bushy or wiry 

 twig growth often resulting from prema- 

 ture pushing of lateral buds. Diseased 

 trees, more or less promptly assume a 

 sickly or yellow color in their foliage. 

 The leaves often have a peculiar roll and 

 droop. After the second year the twigs 

 and branches begin to die back and the 



"The fonrth instalment o{ Ur. Walte's address 

 on "Fnnrons Diseases of Ontario Orchards," 

 Kiven at the last convention of the Ontario 

 Pmit Growers' Assoelation. 



lowing, become even darker colored and 

 larger than normal. That is to say, when 

 the yellows first attacks strong vigorous 

 trees, it sometimes stimulates the tree, 

 both fruit and foliage, before it begins to 

 weaken it. This may even hold true the 

 second year in some cases. The twig 

 growth is shorter on such trees. They 

 behave like trees on which summer 

 pinching of terminal buds is practised. 

 Ordinarily, however, especially on trees 

 under average cultivation, the yellowing 

 of the inside leaves begins as soon as the 

 premature fruit appears. Sometimes 

 these leaves are distinctly rolled upward 

 toward the mid-rib and droop and curve 

 inward by the bending of the leaf stem 

 and mid-vein. This symptom is more or 

 less variable just as the presence of the 

 vellows sprouts may or may not be prom- 

 inent. 



OTHER OATTSES OF YELLOWS 



Many other causes produce yellowing 

 or discoloration of foliage. These other 

 yellow effects need have no relation what- 

 ever to the yellows and, of course, occur 

 on most all trees and plants, whether 

 thy are affected by the yellows or not. 

 Some of the principal causes of yellowing 

 of the foliage of peach trees, in addition 

 to borers and frost' girdling, are starva- 

 tion or poverty of the soil, particularly 

 nitrogen starvation, the fungous root rot, 

 sour soil, root aphis, the root knot or 

 eel worm disease, root winter killing and 

 various other root troubles. These dis- 

 eases, except the fungous root rot, are 

 all mpre or less curable and non-conta- 



gious and, of course, should never be 

 confused with the true yellows. A yel- 

 low peach tree, therefore, does not nec- 

 essarily mean a tree affected by peach 

 yellows. 



BELATED DISEASES OF YELLOWS GROUP 



Two Other diseases should be mentioned 

 in this connection as they belong to the 

 same general group as the yellows. Th •/ 

 are the "little peach" of the northern 

 states and peach rosette of the south. 



(To be continued in next issue.) 



Use a Manure Spreader 



Editor, The Canadian Horticultur- 

 ist : Regarding the use of manure spread- 

 ers in orchards and vineyards, I would say 

 that before purchasing a spreader we 

 found it a very laborious task shaking 

 manure from a wagon. On considering 

 th^ time used and the present high price 

 of labor, we decided to purchase a 

 spreader. We considered the matter 

 over and decided that a forty-bushel 

 capacity was plenty large enough for 

 two horses to handle, as three horses 

 could not be worked among trees in a 

 vineyard very well. This size of a 

 machine being shorter in the gear, was 

 more convenient to turn at the ends of 

 the rows than a larger machine. We 

 are well satisfied with our choice. 



We find that our manure goes a great 

 deal further, besides being pulverized 

 finely and spread evenly, also being easily 

 worked into the soil without plowing it 

 in. I consider this a great advantage 

 and saving of fertility, as you may quick- 

 ly dispose of your manure before it has 

 time to dry out or evaporate in the sun. 

 I also consider that the manure being 

 applied in this manner, that is, spread 

 finely all over the ground so that the 

 numerous feeders of trees and vines 

 may readly avail themselves of it, is the 

 correct way to apply manure. 



If a man has, say, sixty loads of man- 

 ure or over every year, a manure spread • 

 er is a good investment, and as much 

 necessary an implement as any on the 

 farm. It would also be a good invest- 

 ment for two growers or farmers living 

 close together and not having such a 

 large quantity of manure to handle. A 

 manure spreader properly housed when 

 not in use and used intelligently should 

 k:st almost as long as a wagon. — Wni 

 H. Secord, Homer, Ont. 



In spraying, the more distant the tree 

 or plant to be treated, the coarser must 

 be the spray. 



As all good spray machinery is expen- 

 sive, only careless operators will neglect 

 its proper care. 



II 



