250 POMONA COLLEGE JOURNAL OF ENTOMOLOGY 



foliage or fruit and did not penetrate into the waxy covering of the insects. 

 Only upon the trunks of the trees did we get any results worth while — and 

 these results were obtained with all the sprays tried. 



GASOLINE. 



To test a stronger and more volatile solution, gasoline was tried with 

 hope that it might evaporate before any real damage was done to the tree, 

 and yet kill the mealy bug. Accordingly 2^/2 gallons were applied to a large 

 tree. It was impossible to cover the entire tree with so small a dosage, but 

 the desired tests were obtained. After two days the leaves began to curl 

 up and dry upon the tree without falling to the ground. The burning was 

 severe to the fruit as well as to some of the new growth. The killing power 

 was good, but not so good as that of the kerosene. The experiment only 

 shows that this liquid is too severe for a tree's insecticide in its pure state, 

 though it has excellent killing properties. 



RESIN WASH. 



Formula for the stock solution : 



Resin 5 lbs. 



Caustic Soda ( Lye) 1 lb. 



Fish Oil ...1 pt. 



Water to mix 2 gals. 



This stock solution was diluted to make a number of tests, which are 

 recorded as follows : 



Stock solution diluted with water 1 to 48 : — Several trees sprayed with 

 this mixture showed unsatisfactory results, because the waxy covering of the 

 mealy bug seemed to resist it completely. In other words, it would not dis- 

 solve the waxy covering at all, and hence was impracticable. 



Stock solution diluted with water 1 to 24: While this mixture was 

 the best obtained for the mealy bug, and really gave good results, it did not 

 show up as well as did some of the sprays which follow. Its adhesive power 

 is good, but the power of penetration not so good as the emulsions. 



Stock solution diluted 1 to 12 and 1 to 6: These mixtures were little more 

 efifective than the less powerful ones, and much more expensive. 



None of these mixtures seemed to do the least bit of damage to the 

 foliage of the trees. 



POTASSIUM BICHROMATE. 



The killing power of this chemical, when dissolved in water and applied 

 alone, or when added to other solutions, is remarkable. When dissolved in 

 water it has no particular affinity for the waxy covering of the mealy bug. 

 but the deposit left upon the insects upon evaporation makes great havoc 

 among them. In every case the killing was excellent no matter how mixed, 

 but the foliage of the tree could not resist it. The fruit also was badly 

 pitted and spotted wherever a drop gathered and the mineral was deposited. 



