482 EXPERIMENTAL FARMS 



4 GEORGE V., A. 19U 



The question is frequently asked by farmers sending samples of potatoes affected 

 with storage rot, whether there is any treatment to prevent it from spoiling the 

 potatoes. We are afraid there is nothing to be done to stop the decay once it has set 

 in, beyond hand-picking them, removing all damaged, frozen or diseased potatoes, pro- 

 viding good ventilation and using for storage a cool place. 



In the preceding linos we have spoken about the result to be expected from 

 unripe, frozen or damaged potatoes, and have pointed out that, without being actually 

 diseased, they are liable to suffer considerable losses. But how much more quickly 

 will the decay set in when the tubers have been attacked by late blight and other 

 diseases, eventually finding their way into the tuber. 



There are a number of distinct parasitic diseases of the growing potato which 

 will start a ' storage rot,' and which will spread by contact from diseased to sound 

 tubers. Late blight (Phylophthora infestans) is the worst offender in this respect. 

 The amount of late blight present in a field largely depends upon the successful and 

 rapid control of the potato bug. When the potato bug has been allowed to gain a 

 foothold, even if only for a short period, the vines are generally so much injured that 

 it is almost impossible to keep the late blight from playing havoc. 



In some potato experiments carried out at the Central Experimental Farm, with 

 the view of producing potatoes as free from disease as possible under practical farm- 

 ing conditions, we secured from the four acres grown 1,770 bushels, which averages 

 about 440 bushels per acre, by no means a light yield; but, notwithstanding careful 

 spraying, the potato bug had done enough damage before it was controlled, eo that, 

 late blight appeared and still caused far too much loss. Unless spraying is begun 

 very early in the season late blight is difficult to control, and often about August and 

 September the potato tops have been killed. Thus, not only is the manufacture of 

 the reserve food to be stored in the tuber discontinued and the tubers remain unripe, 

 but the disease spreads into the tubers. When this has taken place, the potatoes may 

 be left in the ground for a week or so longer, when the rot will be more apparent, but 

 when digging the potatoes, they should be hilled up on the field, covered lightly with 

 straw and earth until they have dried up well. Before taking them in, the potatoes 

 should be carefully hand-picked to remove all diseased or injured potatoes. 



It is hardly necessary here to mention other diseases affecting the potato plant, 

 for whatever their nature, as soon as the tubers become affected it amounts to the 

 same thing, they must be picked out to prevent storage rot. Diseases like potato 

 rosette or little potatoes (generally known as rhizocionia), fusarium rot and others 

 which may affect the potato tubers must be controlled or prevented by the use of good 

 sound seed. When the potato tuber is once affected it is very liable to decay after 

 being stored. 



I have included in the term ' storage rot ' the various forms known to the plant 

 pathologist and caused by a number of different organisms. There are a number of 

 different bacteria producing a soft or wet rot, and also scores of fungi, which find 

 the prevailing conditions suitable for their growth and development, and produce 

 dry rots and decay of various forms. Whatever form of rot may be developing in 

 storage the prevention of losses will be the same in every case, and may be sum- 

 marized in the following suggestions: — 



1. Sound, ripe and undamaged potatoes will keep in this condition unless brought 

 into contact with tubers showing signs of decay. 



2. The prevention of losses in storage must begin in the field, where the 

 growing plants should be regularly sprayed to prevent diseases likely tn affect the 

 tubers. 



3. Potatoes should be dug when ripe if possible. Care should be exercised to 

 prevent damaging tubers when digging. Frozen and damaged potatoes, as well as 

 those showing signs of disease (with the exception of common scab) should not be 

 placed in storage with sound ones, but must be carefully picked out. 



