TWO LEAFHOPPERS INJURIOUS TO APPLE NURSERY STOCK. 31 



During the spray application with "set nozzles" it was noted 

 that the terminals of an occasional tree were missed by the spray. 

 One reason for this was that the machine was top heavy and easily 

 jolted when passing over a rough or stony place, and this resulted in 

 the spray material being sent over the top of a tree. Furthermore, 

 a few trees would outgrow the remainder of the trees in a row, so the 

 spray material from the "set nozzles" would not reach the terminals 

 of such trees. Nevertheless, sufficiently good results were obtained 

 with the "set nozzles" to warrant their use. 



TREATMENT FOR THE SECOND BROOD. 



An attempt was made to destroy the second-brood nymphs by 

 spraying and dipping upon trees which had received no treatment 

 against the first brood. On the date of this experiment, July 18, the 

 terminal leaves were so badly curled that the nymphs were well pro- 

 tected from the action of the spray. Four plats of about 700 trees 

 were sprayed with a compressed-air sprayer, using 40 per cent 

 nicotin sulphate at various strengths from 1-800 to 1-1,500 with soap 

 added. The counts showed that only 2 per cent of the nymphs were 

 killed on the best plats. 



The dipping work was done with large shallow pans specially con- 

 structed for dipping leafhoppers and aphids on young nursery trees. 

 The tops of the trees were thoroughly immersed in the pans of spray 

 material. The same number of plats and the same insecticides that 

 were used in the spray treatment above were tried in the dipping 

 experiments. The results obtained by dipping were about the same 

 as the spraying results, less than 2 per cent of the nymphs being 

 killed. 



Since such poor results were secured from spraying experiments 

 against the second brood no effort was made to spray the third-brood 

 nymphs, for at the time of the presence of the latter on unsprayed 

 trees the terminals are even further curled and inaccessible to a 

 spray liquid. 



METHODS AND TIME OF APPLICATION. 



Attempts to control the winged adults of leafhoppers by spraying 

 have always proved futile because of the agility of movement of the 

 full-grown insects and because of their immunity to the action of a 

 spray liquid at this stage. This has been demonstrated by previous 

 investigators in the case of the apple leafhopper as well as in the case 

 of other leafhoppers of economic importance. 



A spray treatment to be effective must be applied when the insects 

 are in the nymphal stages. The proper time to spray against the 

 apple leafhopper is at the time when a large number of the first-brood 

 nymphs have attained the third stage of development. For the 



