New York Agricultural Experiment Station. 443 



experiments to determine the susceptibility of psylla 

 eggs to spraying mixtures. 



In a number of orchards sprayed with lime-sulphur during April, 

 1910, eggs were observed in considerable numbers on the trees and 

 many of them were discolored and in a collapsed condition. A com- 

 parison of sprayed and unsprayed trees led to the conclusion that the 

 unusual appearance of the eggs on the treated trees was due chiefly 

 to the spraying, they had received. As it was desirable to have 

 data to corroborate these observations a number of experiments 

 were at once undertaken in pear orchards in the vicinity of Lockport 

 and Medina to test the effects of various contact sprays on psylla 

 eggs which are briefly discussed as follows: 



Lime-sulphur sprays: Experiment No. 1. — On April 8, 1910, the 

 homemade wash (15-20-50 formula) was applied to a number 

 of pear trees on which psylla eggs had been laid in abundance. 

 On account of the thickened condition of the spray, the trees and 

 eggs were heavily coated by the application. Daily observations 

 were made in the orchard but no change in condition of the eggs 

 was detected until April 15, or about one week after the trees were 

 sprayed. At this time occasional collapsed eggs were observed 

 on check and treated trees and these increased in numbers until 

 April 20 when nymphs began to make their appearance. The 

 eggs on sprayed and unsprayed trees in the same orchard hatched 

 in considerable numbers, as shown in Table XI, but the nymphs 

 on the trees receiving the lime-sulphur treatment for the most 

 part failed to reach the young leaves, and apparently succumbed 

 to the action of the spray after escaping from the egg-shells. The 

 destruction of the young psyllas was so great that the sprayed trees 

 were comparatively free from psyllas during the remainder of the 

 season while the check trees were badly infested and lost their 

 foliage in midsummer. 



Experiment No. 2. — Commercial concentrated lime-sulphur solu- 

 tion, 32° B., diluted with nine gallons of water was sprayed on 

 21 Bartlett pear trees which were rather thickly covered with psylla 

 eggs. Some adjoining unsprayed pear trees served as checks on 

 the experiment. Applications of the spray were made on April 9, 

 1910, and on April 16 scattering collapsed eggs were observed on 

 treated and untreated trees. On April 20 a few nymphs appeared 

 on the check trees and their number increased rapidly until all 



