TWO LEAFHOPPERS INJURIOUS TO APPLE NURSERY STOCK. 33 



ticular attention should bo i)aid to wetting every terminal leaf thor- 

 oughly. The application should be made when the majority of the 

 nymphs are in the third stage, which occurs about three weeks after 

 the first nymphs are found in tlie termmal leaves. 



The rose leaf hopper is far less mjurious to the foliage of nursery 

 apple stock than the apple leafhopper. Should the infestation by rose 

 leafhoppers be heavy enough to justify spraying, the same remedial 

 treatment recommended for the apple leafhopper can be used, except 

 that the application should be made three or four weeks earlier than 

 the one for the latter insect. 



SUMMARY. 



The apple leafhopper, Empoasca mali, causes serious injury to apple 

 nursery stock by extracting the plant juices from the terminal 

 leaves; as a consequence the leaves curl, become undersized, and fail 

 to function normally, thereby retarding the growth of the trees. 

 The injury is produced by the feeding of both nymphs and adults. 

 In southern Pennsylvania this species is three-brooded and hiber- 

 nates only in the adult stage. Eggs are laid within the leaf tissue on 

 the imderside of the leaves. This leafhopper is widely distributed 

 over the United States and attacks a great variety of host plants. 



In literature the above species has been confused with another 

 leafhopper which attacks the foliage of nursery apple trees, namely, 

 the rose leafhopper, Emyoa rosae. The latter insect is two-brooded 

 and winter is passed in the egg stage. Winter eggs are deposited 

 imder the bark of apple trees. These eggs hatch about a month 

 earher in the spring than eggs deposited by overwintered females 

 of the former species. 



The rose leafhopper may be distinguished from the apple leaf- 

 hopper by its lighter color and by the absence of the six or eight 

 white spots present on the frontal margin of the pronotum of the 

 latter species. Differentiation between the nymphs of the two 

 species is more difficult. The distinct types of mjury produced by 

 the two insects, however, is a ready means of distinguishing them. 

 The rose leafhopper feeds on the lower leaves and produces white or 

 yehow spots on them while the other species attacks the terminal 

 leaves, curls them, and stunts the growth of the trees. 



Parasites seem to play a far more important role in reducing the 

 numbers of the rose leafhopper than they do in reducing the numbers 

 of the more injurious apple leafhopper. Larvae of dryinid parasites 

 are quite common on the adults of the former while only rarely have 

 they been found attacking the latter. Anagrus epos Girault and 

 Anagrus armatus Ashm. var. mgrriveni^ns Girault, parasites of the win- 

 ter egg of the rose leafhopper, help considerably in checking the num- 



