610 Report op Entomologists of the 



recommended for treating scale insects on citrus trees in California, 

 viz., 1 ounce of fused cyanide of potassium. 1 fluid ounce of com- 

 mercial sulphuric acid and 3 fluid ounces of water for 150 cubic 

 feet of space. As each box only contains 117 cubic feet, the amount 

 of gas used in each box was a trifle more than recommended. 



About 75 apple trees that had been treated with the gas were 

 heeled in and retained for the purpose of noting efl^ect of gas on 

 trees and scale insects. They were examined on four separate 

 occasions between the first of May and September. 



When inspected in June a single live scale insect was found which 

 proved to be a male. No injury to the trees was noticeable. In 

 one case where gas treated stock was sent out a pear tree was found 

 in August, to be infested. This tree with a number oi other pears 

 was sold to the purchaser with a plum {Prunus simonii). The 

 latter was badly infested with the '' Pernicious Scale" and had been 

 overlooked the previous fall when the stock was inspected. Of 

 course the plum tree was brought in contract with the pears when 

 delivered, but at that season the " Pernicious Scale •' is sup- 

 posed to be dormant. There is also a chance that the owner 

 transferred the insects later in the season by handling the trees. 



During the first half of October all of Keene & Foulk's stock was 

 re-inspected. All infested stock required for fall and spring trade 

 was stripped of its leaves, taken up, put through the gas boxes and 

 heeled in. Double the amount of gas used during the spring was 

 used for each box. It was found that where double the amount of 

 potassium cyanide was used part of it was not acted upon by the 

 sulphuric acid, hence the following proportions were used : Potassium 

 cyanide 2 ounces, sulphuric acid 3 ounces and water 8 ounces. About 

 two weeks after the stock was treated a live young" Pernicious Scale " 

 was found crawling on some currant bushes that had been treated 

 with the other stock. On investigation it was found that the work- 

 men had placed these currants on top of a box full of trees and 

 when the box was inverted no cleats were placed on the ground for 

 the trees and currants to rest upon. As a result the weight of the 

 trees forced the currants into the loose soil. Hence there is a 

 chance that the failure in this case was due to the fact that the gas 

 did not reach all the insects on the currants. What the effect of the 

 gas will be used double ordinary strength on the trees, can not be 

 determined until next year. 



