19 



Lemon and citron trees are more sensitive than orange and greater 

 care must be taken not to overdose them. Decreasing the amount of 

 cyanide by ten per cent, when lemon trees are treated is recommended 

 in California. 



Efficacy Of the Gas Applied sufficiently strong and under a 

 tight tent, every living scale insect appears to be destroyed. These 

 perfect results are not always obtained in practice despite of care in 

 keeping the outfit in good order ; but living scales have been found 

 on few of the trees fumigated a few weeks after the treatment. A 



BLACK SCALE, Lecanium olecc Bern. 1, an infested twig; la, an enlarged scale. 

 <From U.S.A. Dept. Agr.) 



The Black Scale has seldom been seen on citrus trees in this country but is very 

 injurious to these trees in California. 



number of trees suffering from Purple Scale have been fumigated, 

 and the eggs as well as the insects themselves have succumbed. This 

 success was unlocked for and may not always follow ; it may also be 

 that some of the eggs escaped although those under several hundred 

 scales examined were all destroyed. 



Experiments conducted in the fumigation chamber owned by the 

 Department of Agriculture and situated near the gates to the Cape 

 Town Docks have demonstrated that when the gas is used somewhat 

 stronger than is the practice in orchards, every scale insect and scale 

 insect egg is destroyed. The Australian Bug was among the insects 



