May, 1921] BIENNIAL REPOKT. 17 



Botany Department. 



Snapdragon Rust and Its Control. — During 1919 the effect of temperature on 

 the germination of snapdragon spores was studied as well as the effect of tem- 

 perature on the duration of the incubation period. In field experiments on 

 the control of the disease the following fungicides were used: cuprammonium 

 sulphate, cupric acetate, sulphur, and sulphur containing 12 per cent bisul- 

 phite of soda. The weather during the greater part of the growing season 

 was cold, and the copper fungicides afforded the best protection. 



In 1920 field experiments were made on the control of snapdragon rust by 

 means of calcium polj^sulphide, sulphur, and sulphur plus varying percentages 

 of soot. The results obtained indicate that sulphur affords better protection 

 than calcium polysulphide, but that contrary to the opinion generally current, 

 the addition of soot to sulphur did not increase its efficiency. 



Potato Spraying. — During 1919 an experiment was undertaken to determine 

 the effect of strength of Bordeaux mixture on the number of applications re- 

 quired to give the best control of late blight. A report of the results has been 

 published in Station Circular No. 22. It was found that absolute protection 

 is afforded when between 24.7 pounds and 26 pounds of metalhc copper are 

 applied per acre, and that whether this amount is applied in weekly or fort- 

 nightly sprayings the results obtained are substantially the same. It was also 

 found that 1 per cent Bordeaux mixture 1 : 0.5 is superior to 1 per cent Bordeaux 

 mixture 1:1 for the control of late blight; 2 per cent Bordeaux mixture 1:0.5 

 applied fortnightly is superior to both 1 per cent Bordeau.x mixture 1:0.5 

 and 1 : 1 applied every week, and that of the two proprietary copper fungicides 

 experimented with, the one giving a mixture rich in copper was superior to the 

 one giving a mixture weak in copper. 



Effect of Temperature on the Keeping Quality of Potatoes. — During 1919 the 

 work on this project was brought to a close. The results have been published 

 in Station Circular 20. 



Entomology Department. 



Control of Apple Maggot. — Further experiments in the effect of poison sprays 

 on the adults of the apple maggot were planned for the summer of 1920. In a 

 preliminary survey six areas were selected near Durham in which the apple 

 maggot was on record as being injurious in. 1919 and in which spraying experi- 

 ments promised facts of interest. 



Control of the apple maggot by means of spraying with poison bait for the 

 adults has been a subject of investigation by several entomologists. At the 

 New Hampshire Station comprehensive studies in this phase of apple maggot 

 control were carried out through several consecutive years. The results indi- 

 cated that under conditions prevailing in New Hampshire there was apparently 

 no satisfactory benefit to be derived from spraying for the adults. It was de- 

 termined to repeat these spraying experiments in 1920. 



The areas selected are well adapted for securing rehable data. Three of the 

 areas are so isolated by fields, strips of woodlands, and other barriers that it is 

 considered impossible that adults of this species might fly to the sprayed trees 



