Studies on Eggs of Apple Pl\nt Lice 31 



with varying strengths of lime-sulfur alone and in combination 

 with nicotine during the past season (1917-18). The results of 

 these experiments conducted on the eggs of A. avenm out-of-doors 

 at the laboratoiy are shown in condensed form in table 5. Some 

 of the series of experiments are also shown in diagram 1 (p. 27). 



Table 5 shows in the left column the date of application of the 

 spray and the source of the eggs for each experiment in the various 

 series, while the top line gives the treatment in each series. The 

 table also shows for each experiment the number of eggs hatched 

 /', the total number of eggs in the experiment and the percentage 

 of hatch. If one chooses to express the effectiveness of the dif- 

 ferent sprays in terms of the percentage of kill, subtract the per- 

 centage of hatch from 100 per cent. The following example ex- 

 plains what is shown for each experiment. The experiment in the 

 upper left corner shows that the eggs were collected from Smith's 

 orchard and sprayed on December 15 with lime-sulfur 1-9. After 

 they had completed hatching, 72 had hatched out of 186, or 38.6 

 per cent. Subtracting 38.6 per cent from 100 per cent gives 61.4 

 per cent killed. This experiment alone shows the ineffectiveness 

 of applying lime-sulfur to eggs during the month of December. 

 The same thing also holds for the month of November, January and 

 the first part of February. The results of the various series of 

 experiments for the above months are not shown in the table, since 

 they are similar to those obtained in December. 



The table summarizes the results of the experiments conducted 

 out-of-doors with lime-sulfur and nicotine, consequently it will not 

 be necessary to give a detailed discussion of the various interesting 

 experiments. An examination of the table shows off-hand, in all 

 the series of experiments where the same material was used, that 

 the greatest reduction in the percentage of hatch always occurred 

 where the treatments were applied near the time of the emergence 

 of the nymph. These observations, then, fully agree with a former 

 statement— the greater the percentage of eggs showing a split outer 

 shell, the greater the percentage of kill. Lime-sulfur 1-9 during the 

 past season did not kill 100 per cent of the eggs in any one ex- 

 periment; however, it did kill 99.1 per cent on March 22; but lime- 

 sulfur 1-6 was more effective, and in two experiments during ]\Iarch 

 killed 100 per cent of the eggs. Lime-sulfur 1-9 combined with 

 nicotine 1-500 or 1-1000 killed 100 per cent of the eggs when 

 applied during the month of March. According to these experi- 

 ments nicotine at the rate of 1-1000 when combined with lime-sulfur 

 1-9 is just as effective in killing the eggs as nicotine at the rate of 

 1-500. This may be true for eggs of A. avence, but when one wishes 

 to kill 100 per cent of the nymphs that have hatched, the nicotine 

 should be used at the rate of 1-500, as shown by Dr. T. J. Headlee 

 in experim.ents conducted on apple plant lice during 1916. 



