402 THE MONTHLY BULLETIN. 



SULPHUR INJURY IN YUCAIPA, 1917. 



By J. B. Hundley, County Horticultural Inspector, Tucaipa, Cal. 



Before entering into a discussion of the points brought out in the following 

 survey, covering every orchard in the Yucaipa Valley which was sprayed before 

 June 20, 1917, it seems wise to state the weather conditions prevailing during the 

 week June 12 to 19. All in this section will remember that the hot wave of that 

 period was unprecedented in recent years. Not only was the temperature 10 

 degrees higher than ever before known in Yucaipa, but the heat was also accom- 

 panied by a desert wind, which was very dry as well as hot. Another unusual 

 feature which rendered the trees more subject to injury was the fact that the hot 

 spell followed a very cold rainy spring. Nearly the entire month of May was 

 cold and wet. 



Maximum temperatures — June 5 to 20: 



June 5, 80 June 9, 86 June 13, 100 June 17, 112 



June 6, 80 June 10, 79 June 14, 106 June 18, 101 



June 7, 81 June 11, 81 June 15, 109 June 19, 98 



June 8, 90 June 12, 91 June 16, 111 June 20, 92 



I am emphasizing these weather conditions because they seem to be the con- 

 trolling element in this spray injury. During the four years we have been 

 combating codling moth, red spider and mildew, we have used exactly the same 

 sprays each season and have never before burned or injured the fruit in any way. 

 Two cases come to my mind of previous years where sulphur alone caused some 

 leaves to fall. In both cases there was absolutely no injury to fruit, and in both 

 cases the sulphur was applied under hot dry conditions, the temperature being 100 

 degrees. 



During this 1917 spray period, namely, May 28 to June 7, the weather was ideal 

 iu that the temperature did not exceed SI. In fact, no injury was apparent until 

 the fifth day of the hot spell, which was from ten to twenty days after the spray 

 was applied. 



In the chart only the spray applied prior to June 20 is shown. Those orchards 

 a record of which is preceded by a star did not receive the third spray, but only a 

 second, which followed the calyx spray in about ten days. Other orchards recorded 

 were sprayed twice before the spray indicated, namely, in the calyx and ten days 

 later. In these the date of spray therefore means the date the orchard received 

 its third spray. In practically all cases where injury resulted from either the 

 calyx or the spray ten days later, sulphur was used in the calyx spray, as in 

 Nos. 8, 9, 10. This injury was very much more pronounced on the Rome Beauty 

 than in other varieties and resulted in a small black spot developing around the 

 calyx. It is quite remarkable that this injury should have developed sixty days 

 after the spray was applied. In all cases of injury of fruit in orchards preceded by 

 a star this injury was around the calyx as described. 



The damage was estimated shortly after the hot spell and before any thinning, 

 which was absolutely necessary in many cases, had been done. Because of this 

 fact the net returns from orchards with a loss in fruit as high as 20 per cent 

 were not affected, as all injured fruit was removed in thinning and enough was 

 left for a good crop. This spray injury was most severe on the southeast side of 

 the trees. It caused large numbers of leaves to fall and burned the fruit to a 

 crisp, where exposed to the sun. In a week the apples showed burned depressions 

 one-fourth of an inch deep. The stem did not seem to have been injured, so the 

 fruit continued to develop around the burned area until it was badly misshapened. 

 Finally the burned area cracked, but the fruit did not drop. 



Another interesting feature brought out is the difference in susceptibility of 

 varieties. The White Winter Pearmain burned the worst, with Gano, King David 

 and Jonathan close seconds. The next most susceptible varieties were Winter 

 Banana, Winesap and Delicious. The Rome Beauty seemed most resistant except in 

 case of the calyx injury described. 



Taking up the combinations as set forth in the table, we find that practically 

 every case where sulphur was used injury resulted. The brand of sulphur used, 

 whether "Atomic," "Sul-paste" or "Milled," seemed to make very little difference. 

 In the case of orchards numbered 95 to 100 where dry sulphur was mixed in the 



