520 Journal of Agricultural Research voi. v, no. ^ 



In its attacks on hawthorns the leaf miner tunnels the foliage in the 

 same manner as that of the cherry. During the course of our studies it 

 has been very evident that the pest is more destructive to certain species 

 of Crataegus than it is to the English Morello cherry. As has been rarely 

 observed in the case of the latter plant, one may find as many as five 

 larvae mining a single leaf. With hawthorns having a relatively small and 

 narrow leaf, as C. geneseensis, there may be an entire destruction of the 

 pulpy tissue, in which event all that remains of the affected leaf is the 

 epidermis, which dries up and ultimately falls to the ground. At the 

 height of an attack, which occurs when the larvae are reaching maturity, 

 hawthorns which are much infested take on a brownish cast and appear 

 as if struck by a blight or swept by fire. In decorative plantings the 

 destructive work of the insect may assume such a character that the 

 attractiveness of certain species of hawthorns as ornamental shrubs is 

 seriously marred. 



About Geneva the sawfly leaf miner is most common in the foliage of 

 an unidentified hawthorn belonging to the Medioximae group, while 

 such species as C. pedicellata and C. punctata, growing in the immediate 

 vicinity of the former, have so far shown little or no injury and are gen- 

 erally exempt from attack. Dr. C. S. Sargent, Director of the Arnold 

 Arboretum, writes that the insect has become established in the plant- 

 ings of Crataegus spp. and that it is especially destructive to hawthorns of 

 the crus-galli group and to C. nitida, C. rotundifolia, C. pruinosa, and other 

 species. Similar conditions exist at the New York Botanical Garden 

 and, as elsewhere, certain species of Crataegus are quite badly infested, 

 while a few species have so far been free from attack. 



In the public parks at Rochester, N. Y., notably Genesee Park, the 

 insect has in recent years become a serious pest. Hawthorns represent- 

 ing a wide range of species and grown in extensive numbers feature promi- 

 nently in certain landscape plantings. In these the sawfly leaf miner 

 has become established, and its destructiveness may be readily observed 

 during May and June. Some haws have been seriously affected, while 

 others have been exempt from injury. Here, again, various hawthorns 

 of the crus-galli group have proved to be very susceptible to the pest, 

 and certain species of other groups have shown considerable injury. 



DISTRIBUTION OF SAWFLY LEAF MINER. 



As a cherry pest the sawfly leaf miner is definitely known to occur in 

 injurious numbers in orchards of English Morello cherry about Geneva 

 in western New York and about Germantown, which is located in the 

 Hudson Valley. It has been reported to the Station as occurring about 

 Schenectady, but the statement of its presence in that locality has not been 

 verified. In view of its occurrence in two communities which are widely 

 separated, it would seem reasonable to suppose that the pest exists in 



