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to July 1. It comes from an area free from tuber moth. This fact is 

 very important, because this potato pest develops rapidly under in- 

 sectary conditions, often destroying valuable host material before it may 

 be put to its proper use. The Idaho Russet variety produces an abun- 

 dance of long, slender, succulent sprouts which are susceptible to easy 

 infestation, and it withstands to a marked degree heavy infestation and 

 other necessary insectary abuses. 



Well matured, small to medium sized tubers, averaging 4 to 8 ounces 

 in weight, possessing an abundance of well formed eyes, are selected for 

 planting. Freedom from cuts and bruises is desirable, since the condi- 

 tions under which the tubers are placed in the insectary makes them very 

 susceptible to destructive rots and molds which gain entrance through 

 such injuries. Lots of tubers which show any appreciable percentage 

 of Fusarium wilt should be rejected, and as far as possible those affected 

 with scab and particularly Rhizoctonia should be avoided. 



Though small seed pieces, split tubers, and seed end pieces have all 

 been tried repeatedly in the interest of economy, careful experimentation 

 has demonstrated that whole tubers produce better and more hardy 

 sprouts under insectary conditions. Sprouts developed from whole tubers 

 seem less dependent on the medium in which they are being grown and 

 consequently are less seriously affected by the fluctuating moisture con- 

 tent of the trays, which may occur under the most careful handling. 



The whole tubers are planted in a prepared soil medium composed of 4 

 parts of light sandy loam to 1 part of screened dairy manure. The top 

 is then covered with % inch of coarse sand, which serves as a mulch, 

 minimizing the danger of drying out and baking under the heated room 

 conditions. Fifteen to eighteen tubers, depending on size, weighing 

 approximately 6 pounds, are required to plant one tray. 



When planted the trays are placed in the production rooms, usually 

 on well constructed racks. These racks should be in the form of evenly 

 spaced shelves not less than 12 inches apart. The weight of each filled 

 tray is approximately 38 pounds, and vertical supports must be placed 

 between the shelves for every 3 trays, allowance being made for sufficient 

 side clearance between trays so that they may easily be installed or re- 

 moved. The first tier of trays is never placed directly on the floor but 

 is supported on i-inch floor strips. 



By stacking the trays checker-board fashion, racks may be dispensed 

 with, but permanent cleat supports on the walls at both ends of the room 

 are needed. A specially constructed tray is used for this purpose. It has 

 a depth of 6 inches on the ends while the sides are the standard 4 inches 

 in depth. By stacking the trays on the wider ends a 2 -inch opening is 

 provided laterally between trays, permitting cross ventilation throughout 

 the entire stack and continued lateral growth of the sprouts from one tray 



