32 N. H. AGR. EXPERIMENT STATION [Bulletin 212 



Snapdragon Rust and its Control. 



As reported in Technical Bulletin No. 22 this year, it was found by O. Butler 

 that snapdragon rust could be controlled by sulphuring in a warm greenhouse. 

 On plants set out in the open, sulphur could not control the disease, even 

 though a temperature of 22° C. or above was maintained for at least four hours 

 each day by being moved into the greenhouse when the temperature outdoors 

 failed to reach the desired point or did not remain at it long enough. The 

 healthy plants in the greenhouse remained so free from disease that they out- 

 grew the inoculated ones more than twenty times measured in terms of green 

 weight. 



It was also found that plants growing in the field can be protected from the 

 snapdragon rust if they are covered by bell jars at night. 



Two rows of snapdragon plants were set out on the north side of the house, 

 liut exposed to the morning and evening sun. Plants inoculated with rust 

 and healthj' plants were planted alternately in the rows. The experiment 

 was begxm on May 27 and ended on August 28, the plants being dusted twelve 

 times during the course of the experiment with superfine flour sulphur. In 

 one row the healthy plants were covered with bell jars at night, and in the 

 other the rusted plants were so covered. The bell jars were removed between 

 8 and 9 o'clock in the morning, except on one or two occasions when the weather 

 was wet and cold. The healthy plants covered with bell jars grew nicely and 

 remained free from rust; the diseased plants covered with bell jars were badly 

 rusted, but possessed some clean fohage and had a mortality of 33 per cent; 

 the healthy plants not covered were all badly rusted and 50 per cent died; the 

 rusted plants uncovered were either dead or dying, 83 per cent being actual^ 

 dead on August 28. 



Sooty Mould. 



An attempt was made to control this disease bj' dusting with sulphur and 

 spraying with calcium polysulphide. The fungicides were applied as soon 

 as the fungus was noticed on the fruit. Both methods were beneficial, and 

 the fruit harvested from the dusted and sprayed trees was more acceptable 

 to the trade than that from the non-treated trees. 



Apple Scab. 



The experiments on the control of apple scab were continued. An attempt 

 was made to determine the minimum strength of Bordeaux mixture that could 

 be used and satisfactory control obtained. Less than 0.5 per cent Bordeaux 

 mixture did not give satisfactory control. 



Miscellaneous Potato Experiments. 



In the course of the work on potato improvement, O. Butler carried on 

 e.xperiments in order to determine the effect of spindling sprout on yield, the 

 effect of the corrosive sublimate treatment for rhizoctonia on regularitj- of 

 stand, the effect of removing net-necrosis tubers on percentage of leaf -roll, 

 and for the purpose of studj'ing the relative fertility of seed pieces cut from 

 the stem-end and bud-end halves of the potato respectiveh^ 



