EXPERIMENT STATION BULLETINS. 447 



Effect on the fruit and foliage. The "finish " of the pears from dusted trees 

 was very much superior to the finish on fruit from sprayed trees which 

 developed considerable russet. 



The foliage of all dusted trees was in excellent condition throughout the 

 season. The lime-sulphur which was used for the calyx apphcation caused 

 severe foliage injury but this injury was not found on trees sprayed with 

 bordeaux at that time. The lime-sulphur injury developed within twenty- 

 four hours after the application of the spraying material. 



CONCLUSIONS FROM RESULTS OF PEAR DUSTING AND SPRAYING EXPERIMENTS. 



Value of the "pre-pink" or delayed dormant application. The results of 

 work in 1920 and 1921 indicate that an application, made just as the blossom 

 buds first show white but have not separated in the cluster, is valuable in 

 the control of pear scab. It seems advisable from experiments conducted 

 thus far that this application be made in districts where pear scab is prevalent 

 and in all sections on varieties which are very susceptible. 



Any of the spraying materials ordinarily used for pears are satisfactory 

 for the "pre-pink" application. Lime-sulphur, 634-50, may be safely used 

 at this time when pear psylla is prevalent. 



Comparative value of dusting and spraying. The control of pear scab in 

 the work here reported has been about equally efficient by dusting and spray- 

 ing, but further tests under different weather conditions will be necessary 

 before any definite statement can be made. The foliage on dusted trees and 

 on those sprayed with bordeaux has always been better than on trees sprayed 

 with lime-sulphur. 



Some Observations on the Control op Pear Psylla. 



The severe outbreak of pear psylla in many districts in 1920 resulted in 

 many demands for information and emphasized the difficulty of controlling 

 this insect satisfactorily with the methods ordinarily used. The treatment 

 which has been generally recommended in Michigan consists of a general 

 cleaning up of the orchard, scraping the bark and making a dormant appli- 

 cation of nicotine sulphate or of a miscible oil in the late fall or early spring 

 to kill the hibernating adults. 



There have been many indications that this treatment will not give satis- 

 factory results when the psyllas are numerous as many of them do not hiber- 

 nate on the pear trees but return to them in the spring to lay their eggs. 



Other methods of control. The fact that the eggs are all deposited on pear 

 trees and may be destroyed by certain spraying materials offers another 

 opportunity for attack. When using this method of treatment one application 

 is made just before the blossom buds begin to separate in the clusters to 

 destroy the eggs and another soon after the petals fall to kill nymphs which 

 have hatched from eggs deposited after the first application or from eggs 

 which escaped injury by it. 



As this method had not been generally used in Michigan, it was necessary 

 to obtain more information as to the best material to use for the first apphca- 

 tion. This information was obtained through the co-operation of the Section 

 of Entomology. A supply of hibernating psylla was secured from Fennville 

 and placed with pear twigs in cages in the Entomological Department insec- 

 tary. Great numbers of eggs were deposited on the pear twigs which were 

 then treated with several materials and combinations of materials and a^. 



