October, '19] PETERSON: APHID EGGS 373 



increase is probably an experimental error. The eggs started to 

 hatch rapidly on March 21 and it was necessary to reexamine each 

 twig before it was sprayed in order to remove or count all hatched 

 eggs. Under these conditions, when it was necessary to work rapidly, 

 it is possible that some of the hatched eggs or eggs where the nymphs 

 had just severed the inner pigmented membrane, were overlooked. 



Chart I shows the results of some spraying experiments with the 

 eggs of A. avence for the season of 1917-1918. Comparing the lines 

 in this chart with those of similar experiments on Charts II, III and 

 IV (spraying experiments with the eggs of A. avence for 1918-1919), 

 there is a decided similarity in the comparative value of various sprays 

 in killing the eggs of A. avence for the two seasons. In a few series of 

 experiments for the two seasons there is a marked difference in the 

 angle at which the lines of various plotted experiments cross the chart. 

 In the 1918-1919 charts the hues are more nearly perpendicular due 

 to the fact that 65 to 70 per cent of the selected eggs in the checks of A. 

 avence hatched in 1919, while in 1918 only 45 to 50 per cent hatched. 

 This difference is especially noticeable with sprays which produce 

 little or no effect on the eggs when applied during December, Jan- 

 uary or February (Expt. t, u, and v). 



Liquid and Dry Lime-Sulfur and Substitutes 



Concentrated liquid lime-sulfur at the recommended winter strength, 

 1-9 (or 1-6) is superior to all other sprays (when used at their respec- 

 tive recommended strengths) in killing the eggs of apple plant lice. 

 Apphcations of lime-sulfur, 1-9 made during March, 1919, killed 92 

 to 94 per cent of all the eggs of A. avence and 89 to 96 per cent of all the 

 eggs of A. pomi (Table I and II and Charts I-V). Lime-sulfur, 1-6 

 is somewhat superior to 1-9, but in no instance did it bring about a 

 complete kill. Casein-lime, 1 gm.-lOO cc. added to lime-sulfur seems 

 to materially increase the effectiveness of both strengths of lime-sulfur, 

 kilUng 98 to 100 per cent during March. The casein-lime used as a 

 spreader was composed of fifty per cent casein (lactic) and fifty per 

 cent hydrated lime. 



Lime-sulfur in a dry state, commercially known as dry hme-sulfur, 

 was given a thorough try out and in all cases where it was used (Expt. 

 5, 6, 7 and 8, Tabic I and Expt. 4-p, and 5-p Table II) at the rate of 

 10, 15 and 20 pounds to 50 gallons of water the percentage of kill of 

 the eggs of A. avence and A. pomi was decidedly below that of con- 

 centrated liquid limo-sulfur, 1-9. For dormant spraying the manu- 

 facturers (Sherwin-Williams Co.) recommend 10 to 14 pounds to 50 

 gallons of water. At the rate of 15 pounds to 50 gallons the greatest 

 percentage of kill of the eggs of A. avence was 78 per cent while 94 per 



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