700 Journal of Agriculture. [lo Nov., 1909. 



time, none are known to witlistand it altogether. The most promising 

 field lies in raising new varieties from seed, and Mr. Sevmour, the Potato 

 Expert, is at present engaged in this work. 



Treatment of Seed Potatoes. 



I. To secure seed free from the living fungus in its interior is not 

 always easy, from the difficulty of detecting it in some cases ; but the 

 difficulty may be overcome to a certain extent if the following precautions 

 are taken : — 



{a) Seed potatoes should only be planted when obtained from a dis- 

 trict known to be free from Irish Blight. In older countries, 

 where the disease has become established, this is almost im- 

 possible, but here in Australia there are, fortunately, districts 

 still free, and where the fungus is not likely to thrive. 

 {b) If the seed tubers are suspected, or, in order to make certain 

 that the fungus is destroyed, they may be sterilized. The 

 ordinary sterilizing of the surface will not serve the purpose, 

 for the fungus is inside the potato ; but Jensen has devised 

 an effective method of treatment. This consists in subjecting 

 the seed potatoes to a dry heat at a temperature of 120 degrees 

 Fahr., not allowing it to fall below 118 degrees Fahr., nor 

 to rise above 132 degrees Fahr. I had some diseased potatoes 

 kept at a temperature of no degrees Fahr. for four hours, 

 but afterwards they produced a luxuriant crop of the fungus 

 in 24 hours, while at 120 degrees Fahr. the spawn of the 

 fungus was destroyed. I have had an apparatus constructed, 

 consisting of a copper cylinder, with a movable basket inside 

 capable of containing a bushel of potatoes, and surrounded 

 by a jacket of water, kept, when necessary, at the proper 

 temperature. After this treatment the germinating power of 

 the tubers is rather improved than otherwise. 

 2. If the seed potatoes were certainly obtained from a clean district 

 there would ha no necessity for treatment for this disease, but with the 

 possibility that they may have com.e from an infected area, or have been 

 in contact with diseased tubers, it would be a wise precaution to disinfect 

 the seed. No one, of course, would think of planting badly-rotted 

 potatoes, but those that are but slightlv affected may escape notice, and, 

 even if detected and rejected, thev might still be a source of danger. I 

 have received potatoes, both from Tasmania and South Australia, in a 

 box, with the living fungus freely producing its spores upon them, and 

 the mere handling of such specimens might be the means of transmitting 

 the disease to clean seed. 



Seed potatoes may be simi)lv disinfected 1>\- placing them in a loose 

 bag and then steeping them in a solution of formalin for two hours. 

 A I -lb. bottle of the proper strength may be obtained from Messrs. 

 Cuming, Smith, and Company, Melbourne, at a cost of is. 6d., and this 

 has to be added to ^2 gallons of water, and, after stirring, it is readv 

 for use. 



Spraying. 

 To prevent tlie spread of this fungus from plant to i^lant by means 

 of spores, there is the well-tested and successful method of spraying. 

 It may be almost completely controlled by the use of Bordeaux mixture, 

 which is now recognised as the most effective fungicide, and a short account 

 of how to prepare and use it is here given. In the orchard this mixture 



