28 Experiment Station Bulletin 345 



administration of the certification work was placed under the direction 

 of the State Department of Agriculture. The Experiment Station will 

 continue to cooperate with the certified seed growers and the State De- 

 partment of Agriculture by making greenhouse tests on seed stocks to 

 be planted for certification. 



During the last year 112.97 acres passed inspection, the largest acre- 

 age certified in any one year since 1921. Five out of the seven growers es- 

 tablished tuber unit plots. The seed from these plots will be used to 

 plant fields entered for certification or sold as foundation stock. 



Eighteen tuber samples taken from fields inspected in 1941 were 

 planted in the greenhouse in Durham. The following varieties were 

 represented: Houma, Chippewa, Green Mountain, Sequoia, Cobbler, 

 and Warba. One eye was taken from each of 100 tubers and these were 

 planted 5 inches apart in greenhouse beds. Typical leaf roll symptoms 

 did not develop except in the Warba variety, and as a result satisfactory 

 readings for leaf roll were not obtained. Even in the Green Mountain 

 variety, where seed pieces were taken from tubers known to have net 

 necrosis, the plants developing from these tubers did not show typical 

 leaf roll symptoms. The plants were etiolated, with long internodes and 

 small leaves. 



In a later planting in the same beds, made in April, two eyes were 

 taken from each of one hundred tubers. In one series the eyes were 

 planted five inches apart; the other eye from the tuber was planted in 

 beds at ten-inch intervals. 



The plants growing five inches apart were similar to those obtained 

 in February and March. The plants with the ten-inch spacing gave defi- 

 nite symptoms of leaf roll. 



Tubers chosen from Green Mountain seed as having net necrosis 

 were planted April 15 in the greenhouse. Eighty-eight per cent of the 

 plants developing from these tubers showed leaf roll on May 15, while 

 12 per cent were healthy. 



Other tubers were chosen as having stem end browning. When 

 these plants were inspected on May 15 and again on May 20, 92 per cent 

 were health)' and 8 per cent showed definite leaf roll symptoms. 



These tests indicate that in the spring grading inspection tubers 

 having net necrosis (leaf roll) may be distinguished with a high degree 

 of accuracy from those having stem end browning. (M. C. Richards) 



Bacterial Ring Rot of Potatoes 



Bacterial ring rot was found in New Hampshire fields in 1941 for 

 the first time. The disease probably has been present in the state for 

 two or three years but had not been reported. Most of the potato grow- 

 ers in New I lampshire purchase certified seed each year. In purchasing 

 such seed the danger of 1 (ringing ring rot on to the farms is greatly 

 reduced. However, when ring rot does get on a farm, how long will the 

 bacteria remain in the soil and serve as inoculum? 



Experiments set up at Durham this year to study this problem were 

 tarried out as follows. In October, 1941, ring rot infected potatoes were 

 placed in the soil in hills at a depth of four inches and ring rot free seed 

 was planted in these hills to determine whether the plants, if the tubers 



