1917 EXTOMOLOCaCAL SOCIETY 



The balance in favour of the liquid would be .still greater on small trees taking 

 less material. If, however, the arsenate of lead were omitted the dust price would 

 fall from 12.6c to 6c and the liquid from 7.;3c to oc, leaving the liquid still the 

 cheaper. 



One must not forget that all the above figures are based on the assumption 

 that the outfit used for the liquid spray was a power one, applying 960 gals, per day 

 of 10 hours, whereas nuiny of our fruit-growers still use the hand pumps, which 

 take double the amount of time, and would thus increase the cost in comparison 

 with the dusting, though the initial dilference in price of the two outfits would oiT- 

 set much of this. 



Experiments on Lakge ArrLiTTfxEES. 



The orchard chosen for the experiments consisted of 162 very large trees 

 almost any one of which was capal)le of bearing 10 barrels and upwards of fruit. 

 The varieties were IJaldwin, Greening, Golden Eusset, Spy, Yellow Harvest, 

 Astrachan, Gravenstein and Twenty-ounce Pipinn. The orchard was in a neglected 

 condition, and had not been sprayed for years. All the trees' were infested with San 

 Jose Scale, some of them badly. Codling Moth abounded in this and other un- 

 sprayed or poorly sprayed orchards of the district, and as the trees extended up 

 to the base of the so-called Mountain, which was covered with uncared for apple, 

 pear, plum and cherry trees, and also with many shrul)s <iiid weeds, the Plum 

 Curculio was more abundant here than in most orchards. The leaves on the ground 

 in spring, as examined l:y Prof. Howitt and myself, showed great numbers of the 

 perithecia of the Apple Scab fungus. 



Before the spraying, the owner of the orchard pruned the trees moderately 

 well, and scraped off the rough bark. Then in order to give the different sub- 

 stances used a fair chance, we sprayed the whole orchard heavily for San Jose Scale 

 with lime-sulphur, strength 1.035 except that soluble sulphur was used on 19 trees 

 (strength l^i/o lbs. to 40 gals.). About lialf the dust plot was sprayed for scale 

 before the buds began to burst, the remainder and most of the liquid plots as or 

 just after the buds burst. Buds began to open May 3nd. All plots were finished by 

 ]\Iay 5th. The spraying for the scale gave satisfactory results on all except six trees 

 wliich, owing to their situation, could not be thoroughly treated. Out of the total 

 of 162 trees, 92 which formed a l)lock Iiy themselves cast of the house were chosen 

 for the dust test, and the remaining 70 were used for the liquid sprays. Of these 

 70 we chose four central rows containing the 19 trees mentioned above for a com- 

 parative test with soluble suli)lnir and calcium arsenate. The rest (51 trees) were 

 treated with lime-sulphur and paste arsenate of lead. 



The Dusted Plot (92 trees). 



The trees were each dusted twic.e, the work being thoroughly done on both 

 occasions. On August 22nd, 61 trees were redusted on one side only, but as this 

 partial application had no visible effect on the trees compared with the remainder 

 either upon insects or diseases, it need not be considered. 



The first dust application was just as the blossom buds were ready to burst, 

 ]\ray 19th and 20th. I delayed it just as long as I could and until a few blossoms 

 had actually opened. The dust, therefore, had an excellent opportunity to get on 

 the base or receptacle of the blossom aiul protect it against early infection with 

 Scab. 



