Arsenical Spray Experiments at Elsenburg. 361 



explains iJic exceptional freedom of these varieties of tipples from 

 i'odliii}^'-m()l li iiifeslatioii in the Elsenl)ur<;' orchard in the 1921 crop, 

 and sh()^\•s tliat the ser.sonal life liistorv varies from year to year, 

 and that the relation between th.' time of blossoming" and time of 

 hatching' of first brood eggs is not constant. 



As the maximum emerg-ence of spring moths in 1921 occurred 

 during the first five days of ]>fovember in 1921, the maximum hatching 

 of first brood larvae occurred from the 5th to the 10th of Novembei'. 

 A spray to be correctly timed should then have been applied the first 

 week of November. In 1921 the earliest first brood larvae appeared 

 in the bands on 15tli November; in 1920, Kith November, notwith- 

 standing the fact that the earliest spring- moths appeared considerably 

 later in 1921. The earliest adult moths of the first brood rmerged at 

 the same time botli years, i.e. 5tli December. Consequently the cor- 

 rect time for applying- the third codling spray was during the week of 

 15th December, or before Christinas, at tlie latest, to poison the 

 earliest hatching second brood larvae. 



Equipment' for Spraying. 



A petrol power sprayer of 1^ horse-power, capable of maincaining' 

 a pressure of 150 to 200 lb. was used in the experiments. It w^as 

 equipped with two spray rods, each with a line of hose and a single- 

 augled nozzle, furnishing a whirling spray through a flat disc, with 

 an opening of medium size. The top branches of trees higher than 

 12 feet were sprayed from a tower. 



General Aerangement of Spkav Plots. 



All spray plots consisted of at least three rows of fruit trees, 

 and those trees selected for records occupied the middle row of each 

 plot. Trees dusted, those sprayed with calcium arsenate, and ten 

 unsprayed check trees were banded for trapping larvae, to avoid as 

 much infestation as possible in neighbouring plots. 



The Efficiency of Calcium Arsenate in Codling CoNriiOL. 



liegardless of the fact that several scientists have reported that 

 calcium arsenate is at least as efficient as lead arsenate in the control 

 of this insect (1)*, the writer has experienced results for two seasons 

 that show the two brands used were decidedly inferior to the latter. 

 Trees spiayed with calcium arsenate produced from 10 to o3 per cent, 

 more wormy fruit than those sprayed with lead arsenate. 



In the 1920-21 season an imported tricalcium brand from a well- 

 known manufacturer was used at the rate of f lb. plus 3 lb. of 

 unslaked lime in 40 gallons (imperial) of water. In the 1921-22 

 season a different well-lviiown imi)orted tricalcium brand was tested 

 at the rate or 1 lb. plus 1 lb. lime in 40 gallons of water. The 

 material used in 1920-21 was obtained direct from the makers, and 

 was manufactured in 1919 or early in 1920. It was very fine in tex- 

 ture. The material used in 192I.-22, obtained from a local dealer, 

 and said to have been made in 1919, was noticeably coarser in texture 

 than the lead arsenate powdei', had ])owers of suspension in water 



* Note. — Numerals in pareaihcscs indicate refeiences to literature at end of aiticle. 



