DISEASES AND PESTS OF PLANTS. 19 



cases have been noticed in this Province, which could be put down to mushroom 

 root-rot (Armillaria mellea). In none of the cases noticed by the writer was it 

 possible to find either fruiting-bodies or rhizomorphs. This is rather surprising in 

 view of the frequency of the disease in the Pacific States and the undoubted presence 

 of the. fungus with us. Very little can be done in cases of collar- rot, the tree being 

 generally in a dying condition before the injury is noticed. It is desirable that the 

 trees be so treated that the wood is well matured by the time cold weather sets in, 

 as late growth and a sappy condition of the tree predispose to all kinds of winter 

 injury. 



FRUIT-PIT. 



Also known as Baldwin spot and bitter-pit. This is one of the commonest 

 diseases of the apple fruit, being found more or less in all districts. It is probably 

 worst in the irrigated districts, although it may be very severe at times elsewhere. 

 In its usual form the disease appears as sunken circular spots, y s to % inch in 

 diameter, on the surface of the fruit. These are often darker in colour than the 

 surrounding surface, at least in the later stages. The skin over the spot is usually 

 unbroken. The tissue beneath the spot is dead and brown, and similar pockets and 

 streaks of dead tissue are generally found scattered through the interior of the fruit. 

 In some cases an apple may be very badly affected in this way with little or no 

 indication of the disease on the surface. In many cases, apples, apparently without 

 blemish when picked, develop the disease in storage. The name " bitter-pit " has 

 been given to it from the bitter taste which the pitted spots are stated to have. 

 This does not seem to be the case with us, the chief injury in most cases being to 

 the appearance and consequently the market value of the fruit. A peculiar form of 

 " core-rot " or " dry-rot " found in certain sections is probably due to similar condi- 

 tions. Cases may be found where one limb of a tree bears badly pitted fruit, while 

 that on the remainder of the tree is either free from the disease or much more lightly 

 affected. There is considerable difference in the susceptibility of different varieties, 

 although none is entirely immune. Northern Spy appears to be one of the worst, but 

 this may in part be due to most of the trees of this variety not being yet in full 

 bearing. Jonathan and Mclntosh Red suffer very little from it, this being another 

 strong point in favour of the latter as an apple for irrigated sections. 



The disease occurs in Europe, South Africa, and Australasia, in addition to 

 North America, and has been studied by many investigators. A great deal has been 

 written on the subject, but as yet the relationship between the factors which cause 

 it and the development of the disease has not been defined with sufficient clearness 

 to .render possible any very definite measures of control being put forward. It 

 appears certain, however, that no parasite is responsible, and therefore spraying or 

 similar treatment is useless. Apparently the trouble is due to the conditions of 

 growth, and probably in particular to climatic factors, such as cold nights following 

 warm days, etc. Some of these factors, therefore, are likely to remain beyond our 

 control. Where a tree produces a few overgrown apples, these are more liable to be 

 affected than if the tree had borne a good crop of normal-sized fruit. Irregular 

 growth caused by drought followed by heavy rainfall or irrigation often results in 

 a bad attack. Those horticultural practices which tend to ensure even growth 

 through the season and the maturing of a good crop of medium-sized fruit are, rather 

 than any special measures, likely to remain the best safeguards against the disease. 



McAlpine, who has been making an exhaustive study of the disease in Australia, 

 finds that where the disease is liable to appear in storage on apples apparently quite 

 sound when picked, " even with very susceptible varieties the development of bitter- 

 pit was retarded by keeping them at an even temperature of 30 to 32 Fahr." He 

 also recommends " that the apples should be picked . . . just when they have 

 reached their full size and on the green side, and placed in cold storage without 

 delay." 



