DISEASES OF PLANTS. 351 



the geuus Valsa (Cytospora), but the author claims that neither the bacteria 

 nor the fungus is the primary cause of the death of the trees but that unfavor- 

 able environment and weatlier and soil conditions weaken the resistance of the 

 trees until these parasites are able to gain a permanent foothold and finally 

 cause the death of the trees. 



Recommendations as to proper soil conditions, cultivation, fertilizers, soil dis- 

 infection, and other points are given. 



[Orchard diseases], C J. S. Bethune (Ann. Rpt. Ontario Agr. Col. and 

 Expt. Farm, .33 (11)00). pp. 3.i-S6). — Experiments were conducted with com- 

 mercial lime-sulphur mixtures in 'combating the apple scab (Venturia tniequaUs) 

 and the pear scab (V. pirina). For the apple scab the trees were sprayed (1) 

 just before the blossoms opened with a 1:25 lime-sulphur solution, (2) just 

 after the blossoms had fallen with a 1 : 40 solution, and (3) 3 weelvs later with 

 a 1 : 40 solution. Ninety-nine per cent of the fruit from the sprayed trees was 

 free from scab, none was russeted, and the foliage was uninjured, except by 

 the first 1: 25 spray, which burned the leaves a little around the tips. 



For pear scab 4 applications were given of the lime-sulphur spray, (1) just 

 before the buds began to burst with a 1:9 solution, (2) just after the buds 

 had opened and before the blossoms had appeared with a 1:25 solution, (3) 

 just after the blossoms had fallen with a 1:40 solution, and (4) 3 weeks later 

 with a 1 : 40 solution. The fruit and leaves were absolutely free from scab on 

 the sprayed trees, while on the surrounding untreated trees both fruit and 

 leaves had a considerable amount of scab. The 1 : 25 solution burned the leaves 

 slightly, but not the 1 : 40. 



Experiments were also conducted on the control of black rot cankers 

 (fiphceropsis malorum) on the trunks and large branches of apple trees. The 

 results indicate that this disease can be successfully controlled by (1) thor- 

 oughly pruning the orchard early in the spring, cutting out and burning all 

 dead branches: (2) cutting out the cankers found on the trunk and main 

 branches, being certain that all the diseased bark is removed, disinfecting the 

 wounds with corrosive sublimate 1 : 1000, and painting with wliite lead free from 

 turpentine; (3) spraying all apple and pear trees at least 3 times with either 

 home boiled lime-sulphur or Bordeaux mixture, applied before the buds burst, 

 just before the blossoms open, and just after the blossoms have fallen. A 

 fourth application of the same spray 2 or 8 weeks after the third spraying may 

 prove helpful. 



A further study of the gumming of peach trees indicates that while inocu- 

 lations of the trunk and branches with the spores of brown rot (Sclcrotifiia 

 fructigena) produced typical gum exudations, this fungus can not be con- 

 sidered as the primary cause of the gumming as a whole. Cultures with the 

 diseased wood from around freshly formed gum masses gave no organisms in 

 most eases, and in those instances in which an organism was grown in any of 

 the media, inoculations with it failed to produce gum exudations from healthy 

 trees. 



Black rot canker (Sphaeropsis malorum), S. B. McCready (Ann. Rpt. 

 Ontario Agr. Col. and E.tpt. Farm. .J.T (1909), pp. .'fl, //2). — An investigation of 

 the black rot canker in Ontario shows that it is the prevailing apple tree canker, 

 being widespread in Ontario and Quebec and apparently more severe in the 

 colder and more exposed sections. It was found attacking the trunk, branches, 

 leaves, fruit, and occasionally the twigs. 



It is claimed that this disease can be controlled by good cultivation, thorough 

 spraying, the careful cutting out of all cankers, and the destruction of all dis- 

 eased rubbish, as was demonstrated during the year by numerous growers. 



