Dec. 20. 191S Cherry and Hawthorn Saw fly Leaf Miner 521 



other localities where sour cherries are extensively grown. However, a 

 careful survey by the orchard and nursery inspectors of the Department 

 of Agriculture in all of the leading fruit-growing counties of the State 

 has failed to find any evidences of the work of the insect except in the 

 foregoing localities. A study of available literature indicates that 

 the insect is not known to occut as a cherry pest outside the State of 

 New York. 



As a depredator of hawthorns the sawfly leaf miner has a wider range 

 of distribution. It is known, as already indicated, as a serious pest 

 of hawthorns growing about Boston, Mass., and it is common on various 

 species of Crataegus growing in the vicinity of New York City, Rochester, 

 Ithaca, Geneva, and Skaneateles, all of which are located in the State of 

 New York. 



APPEARANCE OF THE INJURY 



As implied by its common name, the insect is a leaf-mining species 

 and its work is very characteristic. The injury is first indicated by a 

 small, thin, sinuous channel which finally swells out into a large blister- 

 like area of a light-brown color, resembling that of dead leaf tissues. 

 The attack by the larva of the sawfly leaf miner begins on the edge of 

 the leaf toward the stem and continues along one side toward the leaf 

 apex, the tunnel increasing in dimensions with the growth in size and 

 the progress of the insect. Upon reaching the tip of the leaf the grub 

 reverses its course and works backward toward the stem, consuming 

 the remainder of the pulpy tissues between the main rib and the margin 

 of the leaf. As a result, the parenchyma, or soft cellular tissue, is 

 eaten, leaving the epidermis, which turns brown and forms a large blister. 

 These blisters are very conspicuous on the upper surfaces of the leaves. 

 Oftentimes the whole leaf is mined, but usually with most of the foliage 

 only from one-quarter to one-half of the whole area of a leaf is destroyed. 

 (PI. LI, fig. I.) Only the leaves that first unfold are subject to attack, 

 and during some seasons hardly any of these escape the insect's 

 depredations. The principal damage occurs during the last week of 

 May and the early part of June, or about one month before the harvesting 

 of the fruit. With the disappearance of the larv^ae the leaves most seri- 

 ously affected shrivel, die, and finally drop to the ground, causing 

 defoliation, which varies in importance according to the extent of infes- 

 tation and the influence of seasonal conditions on the rate of growth. 



The actual effect of the work of the insect upon the crop is not easily 

 measured and during most years is perhaps not of serious extent. How- 

 ever, as previously indicated, the destructive power of the pest is mainly 

 exercised on the leaves that unfold with the bursting of the buds. In 

 years of slight precipitation and when new growth is of small extent 

 and of slow development the plant is dependent on such foliage as it 

 carfies at the time, and any extended injury to it must result in a set- 



