256 

 APPLE POWDERY MILDEW (Podospiuvra oxyacantlicB (DC) Winter?), 



Seedling apples sometimes suffer quite severely from this disease, 

 which attacks their young shoot tips, often stunting the growth of the 

 seedlings and preventing them from attaining a suitable size the first 

 season. Compared with the injury caused by the apple thrips, how- 

 ever, that brought about by mildew is surely insignificant and, in New 

 York State at least, hardly warrants any expensive measures for its 

 prevention. The disease usually appears late in September, when the 

 principal growth has been made, and seldom, if ever, spreads to vig- 

 orously growing budded stocks, even when these are in close prox- 

 imity to diseased seedliugs. The malady was not observed on bearing 

 trees in the neighborhood of Geneva. 



The experiments* for the prevention of this disease comprised in 1891 

 about 1,000 American stocks and the same number of French stocks, 

 besides 500 seedlings. As stated in a previous publication,* the results 

 of the first season's treatment of the stocks was entirely negative and 

 the treatments of seedlings which were made on May 21, June 3, 24, 

 July 9, 24, and August 8, as well as the early treatments made on the 

 first three dates mentioned, failed entirely to prevent the appearance 

 of mildew the first week in September. Bordeaux mixture and am- 

 inoniacal solution alone were used, the formulae being those described 

 on p. 262. This failure of the fungicides is considered by the author 

 merely as additional testimony to the fact observed that the mixtures 

 were largely washed off before the disease appeared. On August 7 the 

 French and American stocks were budded with Twenty Ounce, Fameuse 

 and Early Strawberry buds, as described in detail on p. 259, and in the 

 season of 1892 the budded, and such of the stocks as were left unbudded 

 were treated with Bordeaux mixture and ammoniacal solution at dates 

 the same as for all other stocks, viz, May 27 5 June 16, 23; July 7, 21; 

 and August 5. One-half the treated stocks were sprayed 5 times on 

 the first five dates mentioned, the other half were sprayed 6 times. 



No powdery mildew appeared during the course of the season, and in 

 October the results of the treatments were entirely negative. The ap- 

 ple thrips, however, attacked the budded and unbudded stocks and 

 injured them severely. The mixtures had, as might be expected, no 

 effect upon these insects. 



DETAILS OF THE EXPERIMENTS. 



The following pages comprise the details of the experiments, which 

 are removed from the general account in order to render the latter more 

 comprehensible. They will prove of interest only to specialists on the 

 subject. 



"Bull. No. 3, loc. cit., p. 60. 



