378 Report of the Horticulturist of the 



ditions. The first precaution to be taken is not to plant on ground 

 that is badly infested with the fungus. It has been demonstrated 

 that the fungus may persist in the ground for several years, and in 

 cases where the soil is known to be badly infested, no remedy of 

 practical value is known. On some soils applications of lime or 

 wood ashes appear to produce conditions favorable to the develop- 

 ment of the disease." ^^ 



Excellent resnlts have been obtained in many instances by simply 

 soaking the seed in a solution of corrosive sublimate (bichloride of 

 mercury). The seed may be soaked either before or after being cut. 

 Corrosive suhUmate is a ])oison and should accordingly be used 

 with caution. One ounce is used for seven or eight gallons of 

 water. It dissolves more readily in hot water and may then be 

 diluted. It should not be used in metal, but in wood or earthenware 

 vessels. The seed should be soaked for one hour and the same 

 solution may be used again and again. After being soaked the seed 

 should neither be put in contact with scabby potatoes nor in 

 receptacles wiiich have held scabby potatoes or scabby beets. With 

 these precautions the seed may be kept any convenient length of 

 time after soaking before it is planted. 



Manure from animals fed on uncooked scabby potatoes or beets 

 is capable of communicating the scab td the potato crop for which 

 it is used. For this reason manure of this kind should not be used 

 for potatoes or beets. Scabby potatoes should not be used for seed 

 since they are capable of communicating the disease to the new crop. 



Potato Beetle. — Every farmer is so familiar with the potato 

 beetle that a description of it would be out of place here. It 

 has been successfully combated for a number of years with Paris 

 green. Formerly the poison was applied in the dry form, and with 

 good results. But it is now considered much the better practice to 

 apply it in the form of spray. This is especially true since the blight 

 has become so universal, and remedies can be applied for both pests 

 at the same time. The Paris green should be used whenever the 

 beetles appear in sufficient numbers to be injurious. Usually it will 

 be sufficient if the poison is mixed with Bordeaux mixture and ap- 

 plied at the time the potatoes are to be treated for blight. 



Potato Flea Beetle. — This is a little shiny black beetle, about 

 a quarter of an inch long, which attacks the potato and tomato vines 



12 Bulletin 30, R. I. Exp. Station. 



