436 



STATE BOARD OP AGRICULTURE. 



which showed even a very small scab spot. The percentages of the different 

 grades are shown in table 2, 



TABLE 2. DUSTING AND SPRAYING GRIMES GOLDEN^ 1920. 



Material 



Check — untreated 



Lime-sulphur solution 



Sulphur dust 



Copper sulphate dust . 



Number 



apples 



examined 



1489 

 3518 

 2629 

 1705 



Scab, 

 per cent 



89 

 20 

 22 

 68 



CodUng 



moth, 



per cent 



10.0 

 1.9 

 0.5 

 5.0 



These figures show the control of scab by lime-sulphur solution and sulphur 

 dust to have been practically equal but apparently not entirely satisfactory 

 by either. As stated above, any apple which showed even a very small spot 

 of scab was counted as "scabby" and this included many apples which had 

 very small scab spots around the calyx. Many of these spots were deter- 

 mined to be scab only by close examination and it was improbable that 

 apples so affected would be classed as scabby in commercial grading. This 

 point is discussed below under the heading of "commercial grades". The 

 control of scab by the copper sulphate dust was not satisfactory as 68 per cent 

 of the fruit from the count trees in this plot was scabby. This failure to 

 control scab may have been due to several conditions. First, the percentage 

 of copper sulphate in the mixture may not have been high enough; second, 

 the dust was not always applied when the trees were wet with rain or dew 

 and it is probable that such a condition is desirable with this material; third, 

 this material may not be effective on apples under Michigan conditions. 



Control of Codling Moth. The percentage of wormy apples on the check 

 trees was not very high, but the control in the lime-sulphur solution and 

 sulphur dust plots was quite satisfactory. The proportion of wormy apples 

 in the copper sulphate dust plot was high. This dust contained the same 

 percentage of lead arsenate as the sulphur dust but a much smaller amount 

 per tree was used as the mixture is much lighter than sulphur dust and a given 

 quantity covered more trees. It is possible, too, that the sticking properties 

 of the copper sulphate dust are not so good as of the sulphur dust. 



Commercial grades. It was very evident that the actual percentages of 

 scabby fruit as shown above did not represent the true proportions of the 

 different grades as made in commercial packing. The fruit from this orchard 

 was graded and packed by the South Haven Fruit Exchange. To get a 

 comparison of the experimental counts and the commercial grades, reports 

 were secured on one full load from each of the dusted and sprayed plots. 



