New York Agricultural Experiment Station. 941 



not destructive to the " flies " unless combined with the tobacco 

 extract. 



On warm days which followed the sprayings few " flies " were 

 detected, and it was estimated that less than five per ct. of them 

 escaped. In the spring so few of the psyllas emerged that no further 

 sprayings were necessary. 



Similar experiments in many other pear orchards have been made 

 in the years subsequent to 1911, and wherever weather and other 

 conditions allowed the work to be done thoroughly large percentages 

 of the " flies " have been destroyed by these late fall applications 

 and the insects so reduced in numbers that no further treatments have 

 been needed to control them. Where conditions have been unfavor- 

 able for thorough work, or where the psyllas in adjoining orchards 

 were uncontrolled, spring treatments have been found necessary in 

 addition to the fall spraying. The three spray mixtures used — 

 tobacco extract, fish-oil soap and lime-sulphur with tobacco — have 

 been about equally efficient, and perfectly safe to use on the trees. 

 Some orchardists prefer the soap, as it is somewhat less expensive. 



The fundamental experiments in spring spray- 

 Spring spraying ing to control the hibernating adults were made 

 for adults. in the Collamer orchards at Hilton late in March, 

 1910. The psyllas were then very numerous in 

 the large orchard of Bartlett, Kieffer and Seckel pears, and 1,530 

 trees were sprayed either with kerosene emulsion or fish-oil soap. 

 The kerosene emulsion was not effective, possibly because improperly 

 prepared so that the percentages of oil varied on different trees. 

 The fish-oil soap as originally applied, and where used as a supple- 

 ment to the kerosene emulsion, greatly reduced the severity of the 

 infestation. The following spring another test of this kind was 

 made in the orchard of Mr. L. B. Wright at Hilton, in which about 

 800 trees were treated with miscible oil or fish-oil soap. The trees 

 in this orchard had been freed from their rough bark, giving less 

 protection to the insects and greater effectiveness to the sprays 

 used. Both applications were successful, the fish-oil soap being 

 rather more satisfactory. 



Along the same lines as these two tests cooperative work was 

 carried on with twenty-five pear-growers, in which miscible oils, home- 

 made oil emulsions and soapy sprays were used alone or in com- 

 bination with tobacco extract. Of these mixtures the soap solutions 

 alone and the tobacco extract with soap were both efficient and 

 safe, but the emulsions were less satisfactory. 



Psylla eggs have generally been found quite 

 Destroying resistant to sprays at any strength safe to use 

 eggs and on trees at the stage of growth when the eggs 



young larvae, are present. Many different materials and com- 

 binations had been used in early tests, but they 

 proved either harmless to the eggs or harmful to the trees. 



