No. 4.] POTATO GROWING. 365 



or blackish areas, the leaf green fading out as it approaches the spot, 

 which rapidly enlarges and becomes moist and ill smelling. The 

 margins of the under sides of such spots show a delicate frost-like 

 mildew if examined on a moist, cloudy day or in the early morning. 

 This is the fruiting portion of the fungus, and on each spot are pro- 

 duced thousands of little fruiting bodies, each capable of causing 

 another spot. 



The washing of late blight spores down into the soil is directly or 

 indirectly the cause of much of the loss from rot of the tubers both 

 in the field and in storage. The most common dry rot of the tuber 

 in Maine is caused by this fungus. Thorough spraying with Bordeaux 

 mixture (Formula 6) , beginning before the blight appears, and keeping 

 the foliage well coated till killed by frost or the crop is harvested, 

 will reduce the losses from this disease to a minimum. No tubers 

 showing dry rot should be planted. 



When to Spray and how to Spray. 



Begin when the tops are 6 or 8 inches high, and spray every ten 

 days (e\'ery week, if the weather is very cloudy and rainy) until the 

 last of August or the first of September, or later if necessary. In any 

 event, spraying must be begun some days before the average observer 

 will detect blight on the leaves, and the foliage should be kept well 

 coated Avith Bordeaux mixture up to the time the crop is harvested 

 or the tops are killed by frost. Do not stop for rainy weather; this 

 is just the time when late blight spores are formed in profusion, and 

 when infection most easily takes place. It is possible for a spraying 

 just before a rain, even though it is largely washed off, to do more 

 actual good than any other during the season. Moreover, properly 

 prepared IBordeaux mixture, if thoroughly applied, will withstand 

 severe washing if it once thoroughly dries on the leaves. The best 

 results are obtained when the mixture is forcibly applied in the form 

 of a fine mist, not in coarse drops sprinkled over the foliage. 



As is described elsewhere, the nozzles should be so arranged and of 

 sufTicient number and adjustments as to cover the entire row at each 

 application. Do not limit the amount applied per acre to an arbitrary 

 number of gallons, but use enough at each application to thoroughly 

 coat the foliage, whether it requires 50, 100 or 150 gallons per acre. 

 Use a pump powerful enough to develop a pressure of at least 60 

 pounds with all the nozzles open. 



Formulas for Scab. 



Formula 1. 

 Corrosive sublimate, ....... 2 ounces. 



Water, . . . . . . . . .15 gallons. 



The corrosive sublimate dissolves readily in water. Immerse seed 

 tubers for one and one-half hours in this solution. 



