THE POTATO IN BRITISH COLUMBIA. 



63 



rains have 'been heavy, with rotting of the tubers in the ground, it has frequently 

 'been found that hills with " brown-ring " tubers were especially liable to rot. The 

 so-called "jelly end-rot" or "jelly ends," which occasionally occurs in Netted Gem 

 potatoes, is also due to one of these Fuswria. 



If tubers affected with ".brown-ring" are planted, or if healthy tubers are 

 planted on soil infected with the disease, the "wilt" form appears in the growing 

 plants. Such plants show a pale colour, with limp drooping leaves. If the stem is 

 cut across, the vascular bundles, instead of being white, are 'brown. If tubers are 

 present they will probably have the " brown-ring " also, and in this way the disease 

 is propagated. Infected plants may die early, but in many cases they live long 

 enough to produce a crop of infected tubers. 



Control is difficult. Rotation is important, the worst infected areas being those 

 on which potatoes have been grown in close succession for a number of years. 

 Seed-selection is also important, and some very striking results have been obtained 

 where care has been taken. Every seed-tuber should have a thin slice cut off the 

 stem-end and those showing the brown ring discarded. This may be done before 

 disinfecting. If a sample shows 10 per cent, or more of " brown-ring," it is best to 

 discard the whole lot unless no better can be procured. Where a seed-plot is grown, 

 all potatoes showing wilt should be carefully " rogued " out before digging-time. 



Fig. 04. Common scab (original). 

 PARASITIC DISEASES OF THE TUBER. 

 COMMON SCAB (Actinomyces scabies). 



This affects the tubers only and is found wherever potatoes are grown. It 

 appears as round or oval, raised corky spots on the surface, or simply as a thick, 

 irregular roughening of the skin (Fig. 04). It may only form occasional small spots 

 on the tubers, or it may almost cover the entire surface. Early infestation or the 

 additional work of insects sometimes results in pits or cavities, which not only 

 blemish and make extra labour in preparing potatoes for the table, but also expose 

 the interior of the tuber to various rot- fungi. While scabby potatoes, if not too 

 severely affected, are not really injured for human food, they often have an earthy 

 taste, and there is more waste in preparing them for the table. In any case the 

 prejudice on the part of the consumer against scabby potatoes affects the market 

 value, and it is therefore in the interests of the grower to have as little scab as 

 possible. 



Control. Scab is due to a bacterial organism present in the soil or on the seed 

 planted. In the former case it may be necessary to discontinue potato-growing on 

 such land for a time. Seed-disinfection before cutting will prevent the latter. 



