THE CODLING MOTH OK APPLE WORM. No Insect

THE CODLING MOTH OK APPLE WORM. By A. L. QUAINTANCE, In Charge of Deciduous Fruit Insect Investigations, Bureau of Entomology, INTRODUCTORY. No insect enemy of fruits, with the possible exception of the San Jose scale, iá more generally and effectively treated than the codling moth or apple worm, and its control has become one of the routine features of work in many commercial orchards. The treatment for' this insect mostly takes the form of spraying the trees with arsenicals, and great variation is possible in the thoroughness with which the work may be done. Some orchardists are able to reduce the amount of . wormy fruit to a very small percentage of the crop, but the major- ity perhaps fail to obtain best results on account of imperfect spraying and lack of attention to details. In many instances results have been so unsatisfactory as to lead orchardists to doubt the value of the measures recommended, and some hold that these are entirely without merit* While a large amount of fruit is thus needlessly lost through careless spraying there is a still greater aggregate loss in the thousands of small orchards over the country, often of not more than two or three dozen trees, in which spraying is not practiced, the owners not being informed regarding the value of such work or the orchard interest not appearing sufficient to warrant the necessary expense. Notwithstanding the considerable amount of spraying at present practiced against the codling moth its injuries still continue to be very great, resulting in an estimated shrinkage in the value of the apple crop of the United States of approximately $12,000,000 annually; and if account be taken of the expenses incurred in its control for labor, arsenicals, and spraying apparatus an additional sum of probably not less than $3,000,000 or $4,000,000 must be charged to the presence of this insect in the apple orchards of the United States. More thorough and timely spraying where the practice is already established and the adoption of such work where heretofore neglected w;ill result in a great lessening of the present heavy loss suffered from this pest. CHARACTER OF INJURY. Wormy apples (see PL LIII, figs. 1 and 2) are familiar to all grow- ers and consumers of this fruit, and many have seen, on cutting open an apple, the small, pinkish larva about three-fourths of an inch long, the cause of all the mischief. Injury is done only in the larval or 436 436 YEARBOOK OF THE DEPARTMENT OP AGRICULTURE. worm stage of the insect, the larva spending the greater portion of its life within the fruit feeding on the substance of the apple, rendering it more or less worthless and always of inferior grade. Infesta- tion is generally indicated by a mass of brown frass protruded from the calyx end or elsewhere, marking the place of entry of the larva. The effect of the injury will vary according to the degree of ma- turity and the variety of apple attacked. Injury by the first generation of larvae to the green fruit in early summer will cause most of it to fall, and wormy apples comprise a considerable proportion of the so-called " June drop." With some fall and winter varieties fruit injured early in the season may remain on the trees, especially if the injury has not been serious. Later appearing larvœ, as of the second generation, do not cause serious dropping of fruit, though the extent of this will depend much on the amount and violence of the wind. The injury, however, will, exoept when occurring quite late in the season, cause the fruit to ripen prematurely. Thé ammmt of depreciation in the value of the fruit will vary according to the character of the injury. Apples which have been penetrated to the core and in which larvœ have fed until full grown are practically valueless, except for purposes of cider or vinegar. Fruit with only a slight surface blemish on the sides oi* ends is injured mostly in keeping qualities and in appearance, and may have considerable value for ready sale, though it would not be suitable stock for placing in cold storage. In the Middle W^tem ^nd Eastern States especially, considerable fruit which is more or less injured by. the codling moth finds its way into barrels with first-class stock, greatly depreciating the value of the latter. More care is necessary in grading to exclude all wormy fruit, as it often happens that the poor- est and not the best fruit in the package determines its market value. lilFE HISTORY AND HABITS. Since the time of Cato the codling moth has been writt^u about by practically all entomologists, and the combined literature on this species, from nearly all countries of the world, would amount to several good-sized volumes. Nevertheless, it is only within compara- tively recent years that a fairly complete account of the life and habits of the insect has been presented, and beliefs formerly current have been shown to be erroneous.** At the present time numerous impor- « Special mention should be made of the work of Doctor Howard (Rept. Com. Agrie. 1887, p. 88) ; Card (Bui. 51, Nebr. Agrie. Exp. Sta., 1897) ; SUngerland (Bui. 142, Cornell Univ. Agrie. Exp. Sta., 1898) ; Gillette (Bui. 31, n. s., Div. Ent, U. S. Dept. Agrie, 1902) ; Simpson (Bui. 41, Div. Ent, U. S. Dept Agrie, 1903) ; Bau (Bul. 95, Utah Agrie. Exp. Sta., 1906) ; Melander & Jenne (Bui. 77, Wash. Agrie. Exp. Sta., 1906) ; and of Professors Washbum, Aldrich, Cooley, Oordley, Pettit, Woodworth, Lloyd, Sanderson, and others, who have all coor tribute^ la our preeeait knowledge of the insect, and method« of control. THE CiÖDLINö ïtf^TH OB APPLE WOKM. 437 tant points in the biology and treatment of the codling moth need further investigation in various parts of the country to secure data on its behavior under varying seasonal and climatic conditions. The question of the number of generations of the codling moth in different portions of the United States has not been accurately determined, especially in the South and Southwest. The great importance of the insect as an apple pest warrants the fullest investigation of these and other points. - The codling moth, like all insects of the order Lepidoptera, or but- terflies and moths, to which it belongs, presents four distinct stages in its life, namely, the egg^ the larva or worm, the pupa, and the adult or parent moth. THE EGO. The egg of the codling moth is disk-like, somewhat oval in shape, and about the size of a pin head, the shorter diameter varying from 0.96 to 1 mm. and the longer from 1.17 to 1.32 mm. On the surface is a network of lines which becomes coarser toward the flange-like margin. The eggs are glued tightly to the foliage or fruit, appearing under reflected light as a glistening white spot. The egg stage was fully described in 1893. Until about ten years ago the idea generally prevailed that the eggs were deposited either in the blossom end or the stem end of the apple, since the entrance holes of the larvae were usually found at these places. Professor Card in 1897 found that the eggs of the first generation of moths were laid mostly on the foliage, and similar observations were made by Simpson in Idaho in 1901-2, and these conclusions have been fully verified by other workers. In oviposition the moth seeks a smooth place, as the upper surface of a leaf, the pilose or downy condition of the young fjruit at this time rendering it unsuitable for egg-laying purposes. Moths of the second brood, on the other hand, deposit the major- ity of their eggs on the fruit, which by midsummer and later is smooth and more conspicuous. The distribution of the eggs over the plant has an important bearing on the question of the insect's control, as will be pointed out in describing the habits of the young larva. The number of eggs deposited by one female has not been definitely determined, the records (incomplete in some instances) of moths in confinement ranging from 21 to 85. The maximum number under orchard conditions is thought to be not over about 50. Ovi- position probably occurs mostly in the late afternoon or early even- ing, or, according to some writers, at night. The period of incubation will vary considerably, depending on temperature conditions, and eggs are deposited at different stages of embryonic developments Eggs laid by first-appearing moths of the spring generation are usually subjected to a lower mean temperature than those deposited by this generation several weeks, later. Observations by Simpson oil the egg stage under orchard conditions show this to vary between 438 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. nine and eighteen days, with an average of about eleven days. Other observers have found it to be somewhat less, though the observations were made mostly with eggs under indoor conditions. THE LARVA. It is in the larval or " worm " stage only that injury is done. At the time of hatching the larva is of a whitish or yellowish color, measuring fron; one-twentieth to one-sixteenth of an inch in length. The head is proportionately large and shiny black. The cervical and anal shields are dark, and the body is dotted with regularly arranged tubercles, each with a short hair or seta. When full grown the apple worm measures about three-quarters of an inch (19 mm.) in length; the body is of a pinkish flesh color above, becoming whitish below, the general color varying from pinkish to much lighter.

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