286 Bulletin 311 



natural enemies 



The fruit-tree leaf-roller seems to have a number of natural enemies, 

 mostly hymenopterous parasites. We bred at least four species from the 

 larvae and pupae in our cages. In the field Mr. Braucher became much 

 interested in the parasites of this insect and bred many primary and sec- 

 ondary parasites and at least one tertiary parasite. The whole problem 

 is a complicated and interesting one and needs much more detailed study 

 before it is finally cleared up. 



It seemed at first, from the great number of parasites issuing, that the 

 pest would be almost exterminated. As a matter of fact, the parasites 

 seemed to have little effect in diminishing the number of emerging moths. 

 Either the caterpillars of the Ar chips were too abundant to be sensibly 

 lessened in numbers, or the secondary parasites succeeded in preventing 

 the primary ones from becoming effective. The latter theory, however, 

 is hardly probable because there was time for only one generation, and what- 

 ever primary parasites were present probably accomplished their work 

 before being killed by the secondaries. It is quite probable that we over- 

 estimated the number of individual parasites. 



The parasite that was bred in greatest numbers was Pimpla conquisitor 

 (Fig. 70). This parasite appeared in large mmibers and must have 

 destroyed many larvae of the leaf-roller. 



Another species parasitic on the larvae was Amicroplus sp. (Fig. 69). 

 Twenty-three specimens of this small parasite were bred from one larva. 

 Their cocoons, spun on the outside of the body of the host, almost covered 

 it. 



We also reared a single specimen of Phytodietus vulgaris and a single 

 specimen of Sympiesus sp. 



Mr. Braucher reared, in addition, Pimpla inquisitor and Glypta simpli- 

 cipes. These two species seemed to be quite abundant in the field. He 

 also obtained a single specimen of Carcelia nigropalpus. 



Notwithstanding this rather large list of parasites on one host, the leaf- 

 roller was not held in check. The moths issued in abundance in spite 

 of the parasites and deposited large numbers of eggs. 



METHODS OF CONTROL 



The leaf -roller has not proved an easy pest to control. The habit that 

 it has of rolling leaves, tying them together, etc., and then living within 

 these protective coverings, makes it a difficult insect to get at. 



Recommendations have been made to crush the egg masses, at least 

 all that can be found, during the winter when other work is not pressing. 

 It seems to the writer that this is impracticable because the egg masses 



