REPORT OF TEE BOTANIST 251 



SESSIONAL PAPETi No. To 



PLUM POCKETS OR BLADDER PLUMS (ExoaSCUS PlUlli, Fuckel). 



(Plate II. a). 



This disease occurs on the different wild and cultivated plums. The most 

 characteristic effect is the malformation of the developing fruit described by the com- 

 mon names given above. The infected ovary is enlarged and distorted, the texture is 

 spongy and the stone absent. The colour is at first yellowish but later becomes greyish 

 owing to the production of spores on the surface. Finally the bladders turn black and 

 fall. 



The parasite causing this disease very closely resembles that of the Peach Leaf 

 Curl and the treatment there given is applicable here also. It is believed, however, 

 that the mycelium of the fungus may live from year to year in the affected twigs, 

 growing out into the fruit buds and infecting the ovaries. Hence, pruning out and 

 burning of attacked shoots is often recommended. In any case the pockets should be 

 collected, before the spores form, and burned. It is also necessary to treat affected wild 

 trees in the immediate neighbourhood in the same way, or else destroy them altogether. 



A NEW DISEASE OF PEACHES. 



(Plate IV. c). 



Reference should be made to an outbreak of what appears to be a specific peach 

 disease, to which attention was directed towards the close of the year. This disease 

 occurs in the Niagara district and extends into New York state wherever peaches are 

 grown. It manifests itself by larger or smaller cankers occurring on trees of all ages, 

 often somewhat like the common black knot of plums and cherries. Closer examin- 

 ation shows, however, that these ' knots.' are characteristic canker spots. They may 

 occur on all parts of the tree, the main trunk, especially the crotch, smaller limbs and 

 quite young wood. In some instances, the cankers encircle the whole limb rendering 

 it liable to be broken by wind or by the weight of the fruit that may still be produced. 

 As far as could be learned from a personal examination of a number of orchards, the 

 disease is contagious and spreads rapidly. No variety seems exempt from an attack 

 and the age of the tree seems to make little difference. The disease was first observed 

 by growers about four years ago, but no steps were taken to investigate it. It has now 

 become very serious. Photographs have been taken of specimens of the disease and 

 they are reproduced here to enable growers to recognize the malady. They are requested 

 to communicate news of any outbreak so that the extent of the trouble may be ascer- 

 tained. The disease is now under investigation. 



peach leaf curl (Exoascus deformans, [Berk] Fuckel). 



As the name indicates, this is mainly a disease of the leaves. It does, however, 

 attack the young twigs to a considerable extent and the flowers and young fruit occa- 

 sionally. On the leaves, tbe effect of the parasite is to cause a marked increase in 

 the soft tissues between the veins and especially on the upper side. Since the veins 

 tbemselves do not lengthen we find that a characteristic curling and puckering of the 

 leaf takes place to accommodate this tissue. The deformation may consist of only 

 one or two small blister-like spots or it may involve the entire leaf, which also becomes 

 as a whole enlarged and thickened. The colour of the attacked areas is at first a 

 darker green, then reddish, and finally yellow or brown and the leaves fall away 

 prematurely. The new foliage put forth will escape attack but the loss of the early 

 leaves weakens the tree severely and, if at all extensive, the crop is either lost alto- 

 gether or is of inferior quality. The disease is noticeable very early, in fact just as 

 the young leaves are unfolding. 



On the twigs, swellings and distortions are produced and the twig often dies. It 

 was at one time supposed that much of the disease on the leaves was due to the fungus 



