30 PARIS GREEN SPRAYING EXPERIMENTS. 



had fallen from one of the trees while on the other not over 10 per 

 cent remained. Likewise two trees of the same variety, standing side 

 by side in the same row, were sprayed with No. 5 plus lime. When* 

 examined three-fourths of the leaves had fallen from one and only a 

 few from the other. Thus the examination of the orchard failed to 

 show that the spray had any effect whatever upon the falling of the 

 foliage. The tabulated data, however, seem to indicate that a some- 

 what larger proportion of leaves had fallen b}^ December 1 from trees 

 sprayed with Nos. 5 and 6 than from those treated with Nos. 1, 2, 3, 

 and 4. Whether this was due to the sprays or to mere chance in the 

 selection of the trees, it is impossible to say. Little effect if any was 

 produced on the apple, pear, and plum trees. 



As to the effects of the various strengths of soluble arsenious oxid 

 the results of this set of experiments alone seem to show that under 

 favorable conditions, such as prevailed at the time the spraying was 

 done and during the following 30 days, it is safe to spray apple, pear, 

 and plum trees with any of the 6 samples, both with and without the 

 addition of lime. None of the samples injured any of the varieties of 

 these fruits sufficiently for the damage to be considered of practical 

 importance in orchard work. It may be noted, however, that the 

 work was done under peculiarly favorable conditions. Probably not 

 over 15 minutes elapsed in any case from the time the poison was first 

 mixed in the water to the time it was sprayed on the trees, giving but 

 a short time for the arsenious oxid to enter into solution, and the 

 weather conditions were such that after being sprayed on the trees 

 the moisture evaporated very rapidly. Under practical orchard con- 

 ditions it would probably be safer not to use Nos. 5 and 6 on apple, 

 plum, or pear trees without the addition of lime. 



No conclusions can be drawn from this series of experiments as to 

 the peach trees, as these trees in the college orchard are growing on 

 soil entirely unsuited to them. The trees are not thrifty, some of 

 them are nearly dead,, and it is believed that the resistance of the foli- 

 age of the various trees to the action of the soluble arsenic varies 

 greatly. 



SUMMARY. 



The following table shows the maximum amount of soluble arseni- 

 ous oxid in Paris Green which can be safely used on the varieties of 

 fruit trees included in these experiments. It must be remembered 

 when 8 per cent is given as the maximum that this was the strongest 

 solution used, and had stronger ones been employed they might have 

 been found safe also for such trees as endured the 8 per cent solution 

 of soluble arsenious oxid, and these cases are therefore marked "8 +." 

 If even the smallest amount of soluble arsenious oxid was found to be 

 injurious the word "inapplicable" is used, since the sample marked 

 No. 1 is as pure a Paris Green as can be obtained on the market. 



