33 



I have often noticed, and in my writings have frequently called at- 

 tention to the fact, that when used in very hot weather all washes are 

 more liable to injure the tree or fruit than would be the case if used in 

 cooler weather. For use on bearing citrus trees in very hot weather 

 no wash should contain over 5 pounds of 70 per cent caustic soda in 

 100 gallons of the wash; if a greater quantity than this is used at such 

 times there is great danger of marking the fruit in the manner above 

 described. When only resin and caustic soda are to be used, 5 pounds 

 of the latter and 18 pounds of the former in 100 gallons of the wash is 

 as much as should be used in very hot weather on bearing citrus trees. 

 I have never known of a single instance where a wash of this strength 

 has marked the fruit even when used in the very hottest part of the 

 summer season. 



It is interesting to note that the wash used by Mr. Messenger is pre- 

 cisely the same as the one I used on the 7th of August, 1889, in my 

 experiments 199 and 200, an account of which I gave on page 15 of 

 Bulletin 22, referred to above. I there recorded the fact that the wash 

 had produced rusty, brownish spots upon the young oranges, just as 

 Mr. Messenger also found that it would do. 



In traveling about over the southern portion of the State I have 

 frequently noticed that the Black Scale thrives best near the coast, 

 and that in the hot, dry interior valleys a large percentage of them are 

 destroyed by the extreme heat. Even in localities not far from the 

 coast, large numbers of the younger scales perish during the excessively 

 hot weather that sometimes occurs during the months of July and Aug- 

 ust. In fact, in almost any locality these scales will be found in the 

 greatest numbers upon trees having a dense foliage, or which are so 

 situated as to be more or less shaded from the direct rays of the sun. 

 For this reason a judicious use of the pruning knife Avill accomplish 

 much in the way of preventing trees from becoming unduly infested 

 with these scales, while at the same time it will cause the tree to be in 

 a better condition for being treated with artificial remedies. 



The Frosted Scale. 

 (Lecanium pruinosum Coq.) 



Since writing up the account of this species which appeared in In- 

 sect Life, vol. in, pp. 382-384 I have made but few additional notes 

 on this species. One new food-plant must be added to the list given 

 in the above-mentioned account ; this is the common Cork Elm, quite 

 largely grown for ornamental purposes, especially in the northern part 

 of the State. On the 24th of May I received twigs of this tree thickly 

 infested with Frosted Scales ; these were sent by Mr. G. W. Harney, 

 President of the Yuba County Horticultural Commission; and during 

 a recent visit to Marysville Mr. Harney showed me the original tree 

 from which these scales had been taken. Several of the branches on 

 21382— No. 26 3 



