Studies on Eggs of Apple Plant Lice 35 



nicotine, but some of the trees did show a few clusters of curled 

 leaves due to A. sorhi, rosy aphis. A. sorhi is somewhat more re- 

 sistant than A. avencE. 



During 1918 careful observations were made on spraying 

 operations conducted in several orchards throughout the state. At 

 John II. Barclay's orchard near Cranbury the first nymphs 

 emerged on IMarch 21, and 10 per cent of the eggs had hatched 

 on ]\Iarch 30 when lime-sulfur 1-9 was sprayed on 150 nine-year- 

 old apple trees (Duchess). On April 1 about 80 trees of the same 

 variety were sprayed with a combination of lime-sulfur 1-9 and 

 nicotine 1-500. A large number of twigs were collected from 

 sprayed and unsprayed trees and observed on April 1, about ten 

 hours after the combined spray was applied. Since the nymphs 

 were emerging very rapidly on April 1, the difference between the 

 percentage of hatch in the sprayed and unsprayed twigs observed 

 on April 1 can be in part accounted for in the delay of ten hours 

 before the observations could be made. Table 8 shows the effect 

 of the sprays on the eggs and nymphs when the nymphs were 

 emerging. 



On April 8 after all the normal eggs had hatched it was noted 

 that the number of hatched eggs on the unsprayed branches in- 

 creased 13.5 per cent, Avhile the percentage of hatch among eggs 

 sprayed with lime-sulfur 1-9 showed a 5 per cent increase and those 

 sprayed with a combination of lime-sulfur and nicotine did not 

 increase more than 0.5 per cent. This experiment shows that eggs 

 are killed with lime-sulfur sprays and also brings out the increased 

 effectiveness of a combination spray of lime-sulfur and nicotine 

 over lime-sulfur alone. 



The trees were also examined for nymphs. Check trees on 

 April 5 showed 350 aphides to 100 swollen fruit buds, while trees 

 sprayed with lime-sulfur alone showed 25 aphides to 100 buds and 

 the combination sprayed showed 10 aphides to 100 buds. It should 

 also be observed that the lime-sulfur alone did not kill all the 

 nymphs which had emerged at the time the spray was applied, 

 while the combined lime-sulfur and nicotine did kill all the nymphs. 

 Again, the combined spray demonstrated its superiority over lime- 

 sulfur alone as a control measure for nymphs. 



The above sprays were applied by means of one "Hardie" 

 gun attached to a sprayer with 225-pounds pressure. The opera- 

 tor stood on the tank and sprayed the trees on each side of the row, 

 thus giving each tree two applications from opposite directions. 

 This type of instrument is very useful and well adapted to dormant 

 spraying when it is necessary to hit all parts of the tree with con- 

 siderable force. 



On March 28 at J. L. Lippincott Company's orchard, at River- 

 ton, N. J., a combination spray of lime-sulfur 1-9 and nicotine 



