UNITED STATES DEPARTMENT OF AGRICULTURE 



1 BULLETIN No. 438 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



December 11, 1916 



THE PEAR LEAF- WORM. 



By R. L. NouGARET, Entomological Assistant, and W. M. Davidson and E. J. New- 

 COMEB, Scientific Assistants, Deciduous Fruit Insect Investigatix}ns. 



CONTENTS. 



Page. 

 Introduction 1 



History and distribution 1 



Possible origin 2 



Character and extent of injury 3 



Description and habits 4 



Biology 9 



Natural control 17 



Remedial measures 18 



Summary 22 



Bibliography 23 



INTRODUCTION. 



The pear leaf-worm, more scientifically termed the pear sawfly 

 (GymnonycJius californicus Marlatt), is an hymenopterous insect 

 belonging to the family Nematidse and to the subfamily Nematinse. 

 For several years it has been noted as a pest on pear trees on the 

 Pacific coast. The observations and experiments recorded herein 

 were made in California by Messrs. R. L. Nougaret and W. M. David- 

 son, during the years 1911 to 1914, inclusive, and in the State of 

 Washington by Mr. E. J. Newcomer, during the seasons 1914 and 

 1915. 



The injury is caused almost entirely by the feeding of the green 

 wormhke larva and is confined to the foliage, resulting in partial 

 defohation. 



In the localities in which it occurs the insect is quite abundant. 

 Occasionally it becomes a pest of serious consequence, and under favor- 

 able conditions it might cause widespread damage. 



HISTORY AND DISTRIBUTION. 



The p(!ar leaf-worm was describ(;d from 1 female coUectod at 

 Brockport, N. Y., and 10 females taken near Sacramento, Cal,, by 



Note.— This bulletin Is of interest to pear growers generally, but especially to those of the Pociflo coast. 

 67170*— Bull. 4:«— 18 1 



