Studies on Eggs of Apple Plant Lice 51 



A few experiments were conducted with combinations of nieo- 

 tnie and resin fish-oil soap, and these indicate that resin fish-oil 

 soap IS not as effective in combination with nicotine as fish-oil soap 

 made from solid soap. 



Nicotine resinate, containing 40 per cent nicotine, was also 

 given a thorough trial during February and March, 1918, on the 

 eggs of A. arena out-of-doors at the laboratory (table 13). This 

 material behaves like a soap solution and has good spreading and 

 lasting qualities. Nicotine resinate is more effective in killing aphid 

 eggs than "Black-leaf 40" combined with weak solutions of laundry 

 soap. Nicotine resinate at the rate of 1-500 killed 88.4 per cent 

 when the material was applied on March 22, while the same amount 

 of nicotine in "Black-leaf 40" combined with fish-oil soap (solid 

 form), 1 gm. to 50 ce. killed 100 per cent (0.0 per cent hatched). 



All the experiments where nicotine is used show that some 

 eggs are killed with nicotine and where nicotine is combined with 

 lime-sulfur, fish-oil soaps, resin fish-oil soap and resin (nicotine 

 resinate) the percentage of kill is increased, and in a few experi- 

 ments no eggs survived. The experiments also show that the great- 

 est number of eggs of A. aveim are most susceptible to nicotine 

 during the latter part of March, or in other words, when the largest 

 number of eggs show a split outer covering. This brings out the 

 significant relationship between the time of application of the spray, 

 the behavior and structure of the outer semi-transparent layer of the 

 egg, and the susceptibility of the eggs to certain contact insecticides. 



Crude Carbolic Acid, Phenol and Cresols 



During the past two seasons a large number of experiments 

 were conducted with eggs on twigs in the greenhouse, out-of-doors 

 at the laboratory and on young apple trees in the orchard with 

 crude carbolic acid, phenol c. p. cresol U. S. P., meta cresol c. p., 

 ortho cresol c. p., and para cresol c. p. The eggs of all three species 

 of aphides were experimented with in 1917, but only those of 

 A. avence were obtainable during the past dormant season (1917-18) . 

 The results of the following experiments recorded in the various 

 tables show that ciiule carbolic acid gives some promise of becoming 

 an important substance for the control of aphides in the egg stage"^ 

 provided it is applied when the tree is dormant. 



During March and April, 1917, crude carbolic acid only was 

 used and not any of the pure cresols or phenol. The crude acid 

 had a dark brown color and was approximately 100 per cent acid 

 (no water). It was purchased from Eimer and Amend, New York 

 City, at 60 cents per gallon (ante bellum price). According to 

 Merck and Company, i\ranufacturing Chemists, this crude carbolic 



