No. 6. DEPARTMENT OF AGRICULTURE. 75S 



stem end a dark ring is seen, the disease is present, and will appear 

 in the crop grown from them. 



"Since the bacterial disease maj be spread by insects it is even 

 more essential than has been supposed, that the Colorado beetles, 

 flea beetles and blister beetles 'old fashioned potato bugs' be kept 

 in check. Six ounces of Paris green to a barrel of Bordeaux mix- 

 ture is the best preparation for this purpose. Paris green is less 

 harmful to the plants in combination with Bordeaux mixture than 

 alone. The blister beetles and flea beetles are not killed by the 

 Paris green, but the Bordeaux mixture is repellant to them, and they 

 do far less harm where it is used than where no application is made. 

 Where the Colorado beetles are very numerous, hand picking is ad- 

 visable. 



"If sound potatoes are used for seed, blights due to fungi may ap- 

 pear, but the same remedies apply. In that case the Bordeaux mix- 

 ture is more useful than if the bacterial disease alone is present. 

 The poison needs to be used in all cases, for not only do the 'bugs' 

 injure the plants but make openings for the entrance of spores of 

 fungi. It is quite probable that not enough care is usually taken to de- 

 stroy insects affecting potatoes, for, as above stated, they are harm- 

 ful, both directly and indirectly, and unless strong efforts are di- 

 rected against them, other preventive measures are likely to fail." 



Profit from Spraying. — It is safe to say that a thorough applica- 

 tion of Bordeaux mixture should be given potato vines when the 

 flea beetle appears, and tiliis spraying will have an indirect influence 

 against early blight by preserving the vigor of the plants. It may 

 come at such a time that it will be a direct preventive of an attack 

 of this blight for a short period of time. Then the very practical 

 question arises from the grower's decision: Will it be profitable to 

 continue to make thorough sprayings until growth of new foliage 

 ceases^ — five or more additional sprayings? It would be pleasant if 

 one could say definitely that such a course would pay, as we like to 

 engage in profitable work. But experience teaches that local condi- 

 tions must control one's course. If he live in the low^er part of the 

 nortiiern potato belt he has learned to have little fear of the late 

 blight. In one year out of five he may suffer loss from it, and in 

 some sections the chance of loss is very remote. But early blight is 

 a cause of loss to him nearly every year. If he plants his crop 

 early, the ^dnes have filled the middles before time for an attack. If 

 he were spraying, he would have made two applications of the mix- 

 ture before this date to insure coating of the foliage before any 

 germs developed, but several more applications must follow to keep 

 all new and old growth covered, and it is difficult to do this work 

 without injury to the vinos, nnd the work is costly. If the season re- 

 48—6—1902 



