Studies on Eggs op Apple Plant Lice 



33 



April 2 but added "Black-leaf 40" at the rate of 1-500 in order 

 to kill the nymphs. Lime-sulfur 1-9 alone will not kill all the 

 nymphs of any of the three species. A large number of nymphs 

 and adults of each species were sprayed with lime-sulfur 1-9 in 

 the laboratory and only a few were killed, A. pomi being the most 

 susceptible. This also agrees with Dr. Headlee's (9, 10) experiment 

 with A. sorhi in 1916, where nymphs lived and apparently did not 

 suffer with lime-sulfur on their bodies. Regardless of the fact that 

 the lime-sulfur was not applied before the eggs of A. avetice started 

 to hatch, an interesting series of observations were made which 

 show conclusively that lime-sulfur is effective in killing the egg 

 during the hatching period. Two collections were made from the 

 trees in the block east of the house before the spray was put on and 



TABLE 7 



Relation Bet\veen Percentage op Hatch, Percentage op Normal 



Eggs and Percentage op Shriveled Eggs Among Sprayed 



Eggs and Eggs in Check in Table 6 



Check (3) 

 Observed Apr. 3 



Sprayed Eggs (1) 

 Observed Apr. 4 



28.3% hatched 

 33% normal 



39% shriveled 



23.2% hatched 



36.3% normal 



40.5% shriveled 



=: (c) 1.5% difference in shriveled 



Equation: (b) 3.3% -1- (c) 1.5% = (b-|-c) i.8%. approximately equals (a) 5.1%. 



Check (4) 

 Observed Apr. 5 



59% hatched 



14% normal 



27% shriveled 



Sprayed Eggs (1) 

 Observed Apr. 4 



23.2% hatched 

 36.3% normal 



40.5% shriveled = (c) 13.5% difference in shriveled 



Equation (b) 22.3% + (c) 13.5% — (b-|-c) 35.8%, equals (a) 35.8%. 



Note: For complete hiforination read discussion. 



the percentage of hatch in these checks was two or three times as 

 great as in the sprayed twigs collected after the lime-sulfur was 

 applied. Table 6 shows the- various percentages of hatch and per- 

 centages of shriveled and normal eggs found in this portion of the 

 orchard. 



If lime-sulfur is a good control measure, then at any period 

 of observation the percentages of hatch on the spray twigs should 

 not show a marked increase over the first observation of April 4 

 which was made 12 hours after the spray was put on. The first 

 observation on sprayed eggs showed a 23.2 per cent hatch, and a 

 second observation on April 11, which was about five days after 

 all normal eggs had hatched, showed 23.5 per cent hatched, giving 

 a 0.3 per cent increase. On April 14, another collection of twigs 



