THt: AORICULTVRAL JOURNAL. 



025 



ever, I have kuown affected leaves to hang 

 for a couaiderable time. The blighted 

 twigs also become swollen, distorted, and 

 usually curved, whilst the fruit assumes 

 a blotched and blistered appearance where 

 the fungus has invaded the cells, and 

 usually falls without maturing. The fruit 

 of nectarines seems more susceptible to 

 attack than that of the peach. 



The principle features in the natural 

 history of this pest are easily grasped by 

 the farmer who has some conception of 

 the nature of fungus parasites, a subject 

 which I have already dealt with in these 

 pages. At the risk, however, of being 

 considered wordy and wearisome, I will 

 briefly recapitulate some of the more im- 

 portant features as they apply to this 

 disease : If a piece of badly diseased 

 foliage be inspected carefully, and an 

 examination made with a magnifying 

 glass, a floury coating will be noticed 

 upon the affected areas. This has the 

 velvety appearance of the blooin upon a 

 plum, and is due to the fruit of the fungus 

 which has burst through the skin of the 

 leaf. This fruit is carried about by many 

 agencies, and spreads the disease, particu- 

 larly in the early spring, to a great extent 

 That part of the fungus which lies within 

 the tissue of the leaf, and which pro- 

 duces the spores, is known as the wy- 

 celiu/n, and may in a general way be 

 likened to the roots of a plant. It is this 

 mycelium, of course, which does the mis- 

 chief, and like a number of our native 

 plants which are killed off by the frost of 

 winter only to start growing from the 

 roots again in the spring, the mycelium 

 has also the property of resting over from 

 season to season in the wood of its host 

 plant, and producing a fresh outbreak of 

 disease and a crop of spores in the spring. 



The knowledge of this feature has long 

 been in the possession of students, and the 

 opinion was held that this resting my- 

 celium or root of the fungus in the tissues 

 of the tree was the principal cause of the 

 disease. As a consequence, little hope of 

 freeing a tree from the pest has been held 

 out by many authorities in writing upon 

 it. 



Fortunately, however, we are now much 

 better informed since the disease has 

 been thoroughly elucidated by Professor 

 Newton B. Pierce, Pathologist in charge 

 of the Pacific Coast Laboratory of the 



United States Department of Agriculture. 

 Professor Pierce's work and observations 

 are summarised in book form and pub- 

 lished by his Department, the report 

 covering some 200 odd pages. A few of 

 this author's remarks aud his summary 

 are appended for the guidance of farmers 

 troubled with the pest. 



Professor Pierce pertinently says that 

 the losses from the disease, amounting to 

 several millions of dollars annually, in the 

 States, together with the obscure views 

 held by many fruit growers and the total 

 lack of preventive measures, made desir- 

 able the work which he carried out. He 

 claims, as the result, that a thorough 

 knowledge of the disease, coupled with 

 preventive measures, will save all this im- 

 mensei amount of loss and, further, that 

 the disease may be prevented with an 

 ease, certainty, and cheapness rarely at- 

 tained in the treatment of any serious 

 plant diseases. The conclusions arrived 

 at are based upon an immense amount of 

 evidence. Over 1,600 peach growers 

 were asked to test the treatment recom- 

 mended, and so much of this experimental 

 work was done by the fruit growers that 

 it resulted in a saving to the country in 

 one year of three-fourths of a million 

 dollars. 



Summary op Work and Observa- 

 tions ON Peach Leaf-Curl. 

 By Newton B. Pierce. 

 1 Peach leaf -curl has a world-wide 

 distribution, occurring in every region in 

 which the peach is grown. In humid 

 localities it is a leading hindrance to peach 

 culture, and in portions of the Pacific 

 Coast States it has greatly limited the 

 extent of the industry. 



2. The orchard losses from peach leaf- 

 curl vary from a small amount of fruit to 

 an entice crop, while in many instances 

 young trees are killed. The national 

 losses from this disease will amount to 

 3,000,000 dels, annually. 



3. Ctirl is caused by a parasitic fungus 

 known as Exoascus deformans, the 

 ravages of which are largely dependent 

 upon the atmospheric conditions prevail- 

 ing while the trees are leafing out. Rains 

 and cold weather at that time tend to in- 

 crease the severity of the trouble by 

 favouring the growth of the parasite and 

 interfering with the proper functions of 



