8 BULLETI]S^ 368, U. S. DEPARTMENT OF AGEICULTUEE. 



It is evident that spraying is not only of great value in securing a 

 yield, but also in the harvesting operations, and that if the fresh 

 prunes are to be marketed it is absolutely indispensable. 



In the summer of 1915 the rainfaU at Portland, Oreg., 15 miles 

 distant, was below the average and very decidedly so in March, 

 April, and September, the months in which the most critical periods 

 of infection apparently occur. It is the number of damp days 

 rather than the inches of rainfall that actually determines the oppor- 

 tunity for infection, but in this respect also the season of 1915 was 

 not unusuaU}^ favorable to the disease. It seems probable, therefore, 

 that spraying and other remedial measures would be of even greater 

 importance in other years than the results in 1915 show for that 

 season. 



SUMMARY AND CONCLUSION FOR PRUNES. 



The above observations and results indicate that in such seasons as 

 that of 1915 the brown-rot problem is one of great importance to the 

 prune industry in the more humid sections of the Northwest. It has 

 been shown that the apothecia which develop from the fallen prunes 

 are the probable source of the blossom infection. Fall plowing and 

 early spring cultivation ahead of the blossoming period have appar- 

 ently helped to prevent the disease by interfering with the devel- 

 opment of the apothecia. 



The early applications of spray were washed off, showing the 

 importance of the addition of a sticker, but even "with rather unsatis- 

 factory conditions spraying has given fairly good results. The plats 

 given both early and late sprayings with self-boiled hme-sulphur set 

 from two to five times as much fruit as the unsprayed ones, gave two 

 and a half times as large a yield, and had one-ninth as much brown- 

 rot on the harvested and one-eighth as much on the stored prunes. 

 Self-boiled hme-sulphur and Bordeaux mixture have both given good 

 results, but the former has seemed somewhat more satisfactory. 

 Bailey has also reported good results from the use of these fungicides 

 on prunes, 1 



The sticking and spreading qualities are greatly improved by the 

 addition of 2 pounds of resin-fishoil soap to each 50 gallons of the 

 mixture. 



Several years' results ^^'ill be necessary as a basis for any final 

 recommendations, but in so far as the season of 1915 was typical the 

 following schedule of spraying may be suggested: 



The first application just before the blossoms open. 



A second just after the petals have fallen. 



A third three to four weeks later, just after the husks have fallen. 



A fourth about four weeks before harvesting. 



1 Bailey, F. D. Experimental spraying of prunes for control of brown-rot. In Oreg. Agr. Exp. Sta., 

 2d Bien. Crop Pest and Hort. Rpt. 1913-14, p. 241-244. 1915. 



