364 BOARD OF AGRICULTURE. [Pub. Doc. 



case the slugs are abundant, a second application may be necessary 

 inside of two or three days. If the poisons are applied just before 

 the eggs hatch, three applications at intervals of seven to ten days 

 will usually be sufficient during the season. The poisons can be 

 applied alone (Formula 3 or 4) or with Bordeaux mixture (Formulas 

 7,8 and 11). 



Caution: Paris green poisons should never be used alone on potatoes 

 except on the addition of from 3 to 5 pounds of unslaked lime to 50 gallons 

 of spray, depending upon the amount of poison used. 



Potato Scab. 

 Potato scab, which is too well known to need description, can be 

 held in check by planting previously treated seed in clean land. As 

 it is very difficult to get this fungus out of the soil, great care should 

 be taken not to get it in. Soak the uncut seed potatoes one and one- 

 half hours in Formula 1, or two hours in Formula 2, and then spread 

 out to dry. After drying, the potatoes may be cut and planted in 

 the usual way, care being taken not to allow them to touch any box, 

 bag or bin where scabby potatoes have been kept. Treatment with 

 formalin is safer than corrosive sublimate, and on this account is pre- 

 ferred. All tubers treated with corrosive sublimate should be planted, 

 to avoid danger from the poison on them. For the larger grower or 

 seed dealer, disinfection by means of the formaldehyde gas method, 

 as described under Formula 10, is the most satisfactory procedure. 



Early Blight. 

 This disease (sometimes improperly called rust) seldom produces 

 so much damage in any one year as does late blight. Nevertheless, 

 it is widespread, and very destructive in that it attacks and weakens 

 the plant at a critical period, thus checking the development of the 

 tubers. It is confined to the foliage, and is not known to cause rot. 

 Early blight first appears as small brown spots scattered over the 

 older leaves. These slowly enlarge and frequently become somewhat 

 angular in shape, from the fact that they stop on reaching a leaf vein. 

 To control this disease, early, frequent and most thorough sprayings 

 with Bordeaux mixture (Formula 6) are necessary. 



Late Blight or Rot. 

 This disease is caused by a fungus which attacks both the foliage 

 and the tubers. In this latitude it most frequently becomes epidemic 

 during the damp, muggy weather of August and September; it does 

 little damage during hot, dry weather. Late blight may be well dis- 

 tributed over a field before it is noticed, except by a trained observer. 

 As a rule, it first appears on the lower and more shaded leaves, which 

 are hidden from view. Contrasted with early blight, it is more of a 

 leaf blotch than a spot disease. The diseased portions are brownish 



