EXPERIMENTAL SPRAYING AT HIGH MOOR FARM. 89 



sulphur. Attention is again called to the fact that one pound 

 of the dry arsenate was added to each 50 gallons of the bor- 

 deaux mixture and lime-sulphur used. This smaller amount 

 of the insecticide when used alone in 1913 reduced the amount 

 of scab, as compared with the unsprayed check from 39 to less 

 than 16 per cent. 



A large amount of fruit russeting was experienced in the 

 experimental orchards in 19 13, apparently due to natural 

 causes, but this was materially increased by the action of some 

 of the sprays. With bordeaux mixture and lime-sulphur the 

 per cents of russeted apples showed an increase of 38 and n 

 resectively over that recorded for the unsprayed check, while 

 russeting on the plot sprayed, with the larger amount of arse- 

 nate of lead alone was even less than on the check. On ac- 

 count of the last mentioned fact the relative value of the arse- 

 nate of lead spray was still more apparent that season. About 

 12 per cent more perfect apples were obtained with it than 

 where standard dilution lime-sulphur was used. 



Neither in 1914 nor in 191 5 did scab develop sufficiently to 

 give a rigorous test of the fungicidal properties of arsenate ol" 

 lead. In scab control in 1914 two pounds of dry arsenate or 

 lead in 50 gallons of water fell about 3 per cent behind standarl 

 dilution lime-sulphur containing one-half of this amount of the 

 insecticide, but on account of freedom from russeting with the 

 former the per cents of merchantable apples were practically 

 the same. In 191 5 the combined lime-sulphur and arsenate of 

 lead gave a fraction of one per cent better scab control, but on 

 account of russeting, only about 90 per cent of the apples were 

 merchantable. In contrast with this, because of freedom from 

 russeting, the larger amount of arsenate of lead used alone 

 gave over 97 per cent of the same grade of fruit. 



Strong fungicides for the first application followed by arse- 

 nate of lead alone: The aparent high efficiency of arsenate in 

 apple scab control, as indicated by the above described experi- 

 ments, suggested the following possible modification of summer 

 spraying practice. Use a strong fungicide combined with a 

 smaller amount of arsenate of lead when the fruit burls are 

 showing pink. For all later applications depend entirely on ar- 

 senate of lead for the control of both scab and chewing insects, 

 using at least two pounds of the powder or 4 pounds of the paste 



