SOCIETY OF NORTHERN ILLINOIS. 315 



large gardens, and orchards of medium size. The best nozzle 

 tested by him is the common Nixon, and he mentions also the 

 "Pacific Cyclone Spray Tip," highly recommended by 

 orchardists in California. 



TIME OF THE YEAR. ' 



Cook insists especially upon the point that care should be 

 taken to postpone the spraying until after the blossoms have 

 fallen, in order to avoid poisoning bees and other useful insects 

 which visit the flowers. He thinks, also, that less damage has 

 been done by the arsenical insecticides when applied in May 

 than when used in June and July. In late application, he con- 

 sequently reduces the strength. 



REPETITIONS OF SPRAYINGS. 



Cook remarks, with respect to apples, that if no heavy rain 

 follows, one application should be sufficient, but if it does, espe- 

 cially if the trees bear sparingly, it will often pay well to spray a 

 second time two weeks after the first. He doubts if a third spray- 

 ing is profitable, even after heavy rains. 



Popenoe made, in Kansas in 1888, some elaborate experiments 

 designed to test the benefit of repeated spraying. An average 

 of his percentages drawn up from ninety-five trees showed a 

 gain of only three and two-tenths per cent, by a second spraying 

 made nine or ten days after the first. 



TIME OF DAY. 



All that mention the matter are agreed that the best time to 

 apply the dry poisoning is early in the morning, when the plants 

 are still wet with dew. Dry and windy weather are unfavorable to 

 an even and economical application. The wet poisons, on the 

 other hand, may best be distributed in the afternoon, or at least 

 after the dew has disappeared. Dry weather is most favorable 

 for these. 



EFFECTS ON THE TREE. 



Apple. The exceedingly variable action of the arsenites upon 

 the foliage of the trees treated with them has led to a variety of 

 experiments to determine, if possible, the conditions governing 

 this matter. Prof. Cook, for example, sprayed last June, fifteen 

 apple trees, and estimated several days thereafter the amount of 

 leaf injury exhibited. Only three of these trees were noticeably 

 hurt, and these were very badly scorched, the mixture being a 

 pound of London Purple to a hundred gallons of water, applied 

 late in June, a rain following the next day. 



By far the most elaborate study of this subject reported by any 

 one, is that made by Popenoe, of Kansas in 1888. With a view 



