24 



In experiments 258 and 260 the bisulphide of lime (CaS 2 ) was 

 formed, but this did not prove as destructive to the scale-insects 

 sprayed with it as was the case where a certain amount of salt had 

 been added to it. From this it would appear that the bisulphide does 

 not of itself and aloue constitute the insecticidal property of this wash ; 

 at the same time, my previous experiments prove that salt alone simply 

 dissolved in water possesses very little value as an insecticide. Still, 

 when these two substances are combined, the resulting solution pos- 

 sesses much greater insecticidal properties than does either of them 

 when used separately. 



In making the above experiments I was aided in the mechanical part 

 of the work by Mr. 0. H. Richardson, of Pasadena, who kindly placed 

 his infested fruit trees at my disposal. 



The first rain which occurred after the above experiments were made 

 began on the morning of February 15, and continued almost incessantly 

 for the space of two days and one night. Two days later this was fol- 

 lowed by a long-continued rain. Since the solution was upon the trees 

 for the space of about four days and five nights before the rain began, 

 it would appear that it had sufficient time in which to act upon the 

 scales before being washed off by the rain, and that its effects upon the 

 scales would have been about the same had no rain occurred for several 

 months after the various solutions were applied to the trees. 



The wash used in experiment 261 is practically the same as the one 

 in common use all over this State for the destruction of the San Jos6 

 Scale on dormant deciduous trees. Still, as stated above, it did not 

 prove fatal to all of the scales sprayed with it. Even when used one- 

 half stronger than this, as it was in experiment 259, it did not destroy 

 all of the scales sprayed with it. These and other experiments which 

 I made with this wash during the past winter confirm the opinion ex- 

 pressed in my preceding report, to the effect that this wash is not as 

 effectual as the resin wash made one half stronger than when used on 

 citrus trees. I have given a full account of this resin wash of the above 

 strength on pages 27 to 30 of Bulletin No. 23, referred to above; so it 

 will be unnecessary to more than give the formula in this place : 



Resin pounds.. 30 



Caustic soda (70 per cent strong) do 9 



Fish oil pints.. 4£ 



Water, sufficient to make gallons 100 



This wash can only be used upon dormant trees. Owing to the fact 

 that in some portions of the State the winter rains interfere to a great 

 degree with the spraying of the trees at that season of the year, fre- 

 quently rendering wholly ineffectual the labor of a whole day and mate- 

 rially lessening the insecticidal effect of the wash used during the 

 preceding week, it is the custom with some growers to confine their 

 spraying operations entirely to the rainless summer season. At this 

 season, of course, it would be impossible to use as strong a wash as 



