Circular No. 1 16. 
 
 
 United States Department 
 
 BUREAU OF ENTOM 
 L. O. HOWARD, Entomologist and 
 
 THK LARGEB CORN STALKS 
 
 i Diatrcea saccharalis Fab. » 
 
 By <il OBGI l i. AlNSLIE, 
 
 Associah Professor of Entomology, Clemson Igricultural College of South 
 
 Carolina. 
 
 INTRODI CTION. 
 
 In many southern cornfields a heavy wind late'in the season, be- 
 fore the corn is matured, doe- great damage by breaking the plants 
 off at the surface of 
 the ground, thus 
 ruining them. An 
 exaininal ion of i hese 
 broken stems will, in 
 most cases, show that 
 t h ey have b ee n 
 greatly weakened by 
 the burrows of a 
 larva or caterpillar. 
 Tin- larva ( fig. 1 ) is 
 known a- "the lar- 
 ger corn stalk-borer " 
 {/>/',//,<> lara- 
 
 lis). It- work is 
 largely within the 
 stem of the plant and 
 i- so concealed that. 
 in most cases, unless weather condition- make it conspicuous, the 
 presence of the insect passes unnoticed. 
 
 Pio. 1. -The larger corn stalk-borer \l>i'it,<i<i saccharalis) : 
 a. Summer form of larva : h, • , hibernating forms of 
 larva;; •/. third thora nenl from above; e, eighth 
 
 abdomlna I si gmi at I t> >m aboi e ; f, abdominal s< 
 from 1 from side. ■/. >>, c, Enlarged; d, <. f. 
 
 still more enlarged. (Redrawn from Howard 1 
 
 "This i.s pra.'ticnlly :i revision of Circular No. 16, prepared many years 
 aqp by It. 1.. < ». Howard. .Mr. Alnslle was formerly in the employ of this 
 Bureau as an agenl and expert in cereal and forage insed investigations, ami 
 this pesl was "in' of the subjects >•( investigation assigned to him. He after- 
 wards ■ 1 i « 1 some work upon the s|ie,irs for the South Carolina Agricultural 
 Experiment Station in cooperation with this Bureau. 
 2 1 7:; 1 -NO. lie. LO 
 
This insect seems to have been originally an enemy of sugar cane 
 and to have first transferred its attention to corn in the southern 
 part of this country, where corn and cane are grown over the same 
 territory. It occurs in many countries where sugar cane is the staple 
 crop, and has caused great damage in the West Indies, British Guiana, 
 Australia, and Java. The bulk of the evidence goes to show that it 
 was first brought into this country with the importation of sugar- 
 cane cuttings from the West Indies and Central and South America, 
 where, since early times, it has interfered with the production of this 
 staple. 
 
 In the United States this borer is found almost universally through- 
 out the South, from Maryland to Louisiana and westward to Kansas. 
 Among other localities it has been reported to the Bureau of Ento- 
 mology from Bennettsville, S. C, as destroying corn, especially that- 
 planted early in the season. From Waynesboro, Ga., in 1909, reports 
 were received that in some fields the corn was " at least one-third 
 destroyed " by an insect which later proved to be this species. In 
 Virginia it has been found recently at Nathalie, where it was studied 
 by Mr. J. A. Hyslop, of this Bureau, at Allenslevel, at Church Road, 
 and at Farmville. In late October, 1909, Mr. E. G. Smyth found 
 that nearly one-half of the cornstalks at Diamond Springs, Va., 
 were infested, often as many as three larva 1 being found in one 
 stalk, boring from the surface of the ground clown to the base of 
 the root; and while the author has frequently found as many as 
 a dozen larvae in a single stalk, there are never more than two or 
 three pupse in the same stalk. In each case it had damaged the corn. 
 and especially that planted early in the season. Detailed investi- 
 gations of this insect have been conducted by the author during the 
 last two years, chiefly in South Carolina. 
 
 NATURE OF DAMAGE. 
 
 Corn is damaged by these caterpillars in two ways. First, in the 
 early part of the season, while the plants are small, they work in the 
 " throat " of the young corn, and if the tender growing tip within 
 the protecting leaves is once damaged all chances that the plant 
 will become a normal productive specimen are gone. In many sec- 
 tions of the South this is commonly known as " bud- worm " injury, 
 and though there are several other insects which cause a similar 
 mutilation of the leaf, a very large proportion of the so-called " bud- 
 worm " damage may be charged to this insect. The effect of its 
 work on the leaves of the young corn plants is similar to that re- 
 sulting from attacks by the corn billbugs (Sphenophonis spp.) and 
 is evidenced by the familiar rows of small circular or irregular holes 
 across the I 'lades of the plant (fig. 2). 
 
 The other form of serious damage chargeable to this pest occurs 
 later in the season. The larva', having then left the leaves and 
 [Cir. i 16] 
 
descended to the lower part of the stalk, tunnel in the pith. (See 
 fig. 3.) If the larvae are at all numerous in the stalk, their burrows 
 so weaken the plant thai any unusual strain will lay it low and 
 destroy all chance of its maturing. While frequently ten or more 
 larvae may live and mature in one plant, it musi be remembered that 
 
 Pig 2. — Work of larger corn stalk-borer, mutilation of leaves of corn bj larvse. 
 
 Great] reduced (< Original.) 
 
 any infestation, however light, will lessen in some degree the vitality 
 of the plant and cause a corresponding loss in the quality and quan- 
 tity of the harvest. 
 
 HABITS OF THE I.Ai;\ .11. 
 
 [mmediately upon leaving the egg in spring, the young larva of 
 the first generation, spinning a silken thread behind it, wander- 
 down into the throat of the plant as far as the water or dew usually 
 standing there will allow it to go, and begins to (rcA on the leaves, 
 g back and forth through the yet unfolded clusters and -non 
 riddling the more tender leaves with aimless burrows. If the bur- 
 row reaches the tender terminal bud where the future joint- are 
 being formed, further growth at that point ceases and the plant he- 
 come- stunted and misshapen, with no tassel, ks the plant continues 
 to mature, the larva "grows out." as the farmer- say. It i- more 
 LClr. 1 16] 
 
likely that it is the evidences of its work and not the larva itself 
 that "grow out;" but for whatever reason, the caterpillar soon leaves 
 the more leafy portion of the plant and attacks the stalk at or near 
 the ground. Here a hole is cut through the outer wall of the stalk 
 and the larva burrows upward for a short distance, after which it 
 seems to run aimlessly through the pith, frequently even leaving the 
 
 PIG. :'.. — The larger corn stalk-borer: Larva in lower part of com plant preparatory to 
 hibernation. Reduced. (Original.) 
 
 stalk entirely and reentering it at another point. Tinning upward, 
 the caterpillar, when fully grown, bores toward the outside and 
 cuts a circular hole in the outer wall of the stalk. Then, after 
 spinning a few loose threads across this opening to keep out un- 
 desirable visitors, it retreats a short distance, plugs the burrow below 
 with digested pith, and in the chamber thus created slowly changes 
 to the next or pupal stage (fig. 4, c). 
 [Cir. no] 
 
Seldom is the stalk damaged above the third joint from the ground, 
 although the larvae, when small, arc found in the large midribs of 
 the lower leaves and later in the season, when the food suppl}' is 
 restricted, even in succulent nubbins farther up. They sometimes 
 also penetrate the underground pari of the stalk in feeding and enter 
 some of the larger brace roots for a shorl distance. 
 
 The larvae of the second general ion work in a similar manner, except 
 that at the time they appear the tassel has been formed; hence the 
 damage is now confined altogether to the lower stalk. Thus, instead 
 of arranging to pass the pupal stage in the upper stalk, they pene- 
 trate to the rool to hiber 
 
 nate and there, as larva?, 
 pass the w inter in a qui- 
 escent state ( fig. 3). 
 
 SI \-"N \i. HISTORY. 
 
 During the winter this 
 enemy of corn is to be 
 found as a robust, creamy- 
 white larva of the second 
 generation in the lower 
 part of the stalk — or of 
 the stubble, if. a- i- usu- 
 ally the case, the corn 
 has been cut. In this lo- 
 cation the larva form- a 
 small ea\ it v below t he sur- 
 
 b 
 
 Fig. I. The larger corn stalk-borer: </. Female 
 moth : b. wings hi' male : i . pupa. All sum. what 
 enlarged, i Original. > 
 
 face of the ground, well protected from birds, predaceous insects, 
 and unfavorable weather condition-. From the time the corn is 
 mature in the fall until ahoui corn-planting time in the spring this 
 caterpillar remain- inactive. About the time the ground i- being 
 prepared for corn, from March 1.". to April 30, depending on the 
 locality, this larva changes into a reddish-brown pupa or chrysalis 
 (fig. I. >) . A ft ei' a further period of ten or more da\ -" inactivity the 
 adult in-ect emerges from the pupa case as a pale brownish-yellow 
 moth (fig. t, a, 6 ), with a spread of wings of about an inch and a quarter. 
 The moth- then mate and the female- begin at once to deposit eggs 
 on the underside of the leave-, the larv;e hatching from these eggs 
 forming the first generation. 
 
 The eggs hatch in from seven to ten days and the young larva? 
 begin their destructive work in the upper leafy portion of the plant, 
 later descending to the base of the -talk, where they attain full 
 growth. This period, from egg to full grown larva, requires from 
 twenty to thirty days, depending largely on the weather conditions 
 
 [Clr. 1 16] 
 
and the vigor of the plant. The larva 1 when full grown pupate in 
 the stalk, usually in the second or third joint from the ground, and 
 in from seven to ten days the adult moths of the first generation 
 emerge. 
 
 The eggs for the second generation are laid in similar positions 
 on the lower leaves or on the stem, and the larva 1 , after feeding for 
 a short time on the leaves, go directly to work in the stalk, completing 
 their larval growth in the pith of the lower stalk as did the larva; 
 of the first generation. No damage is done to the upper part of the 
 plant by larvae of the second generation. 
 
 By the time the larva? of the second generation are full grown 
 the corn is rapidly nearing maturity, and, instead of pupating in 
 the stalk, they turn downward, penetrate to the extreme lower tip 
 of the taproot, and there form a small cavity in which to pass the 
 winter. At this time the larva? lose the darker markings of the ear- 
 lier forms, and as overwintering larva? are creamy-yellow in color. 
 They are plump and active in the fall, but flabby and sluggish after 
 fasting throughout the winter. The only way in which the insect 
 passes the winter is in the form of this overwintering larva, found 
 below the ground in the extreme lower tip of the corn roots. Two 
 generations a } r ear aj^pear to be the rule, although it is possible that 
 in the far South and on sugar cane a partial third generation may 
 occur. 
 
 DESCRIPTIONS. 
 
 Egg. — The eggs are flat and scalelike, almost circular in outline, 
 and are placed in rows or irregularly, overlapping one another 
 shingle fashion. From two to twenty-five eggs are laid in one place 
 on the underside of a lower leaf or occasionally on the upper side 
 and on the stem. Creamy-white when first laid, they gradually 
 change to a reddish-brown, and in seven to ten days a minute, bristly, 
 reddish caterpillar cracks the shell and crawls out through a narrow 
 slit at one end. The eggs are about three one-hundredths of an inch 
 (7.G mm.) long and about two-thirds as wide. After hatching, the 
 white papery shells are soon washed off the leaves. 
 
 Larva. — The larva of the first generation (fig. 1. a) when full 
 grown is a robust, dirty-white caterpillar 1 inch in length, thickly 
 covered with round or irregular dark spots, each of which bears a 
 short, dark bristle. When the larva is small these markings are 
 almost contiguous, giving the whole insect a dark color and a hairy 
 appearance. The head and thoracic plate of all the stages are 
 brownish-yellow. The overwintering larva of the second generation 
 (fig. 1, 6, c) gradually loses the darker markings of the body and 
 after the last molt remains unspotted and light yellow in color. 
 excepl for the head and the thoracic plate, which retain the brownish- 
 yellow of the earlier stages. 
 [CIr. i nil 
 
Pupa. -When first formed, the pupa (fig. l. - I is light honey- 
 yellow in color, soon changing to a rich mahogany-brown. Ii is 
 about seven-eighths of an inch in length and is able to contorl itself 
 violently when disturbed. It lies in the cavity usually with the head 
 up. On emerging, the moth leaves the brownish shell of the pupa 
 case, partially withdrawn from the hole. 
 
 Adult. The female moth (fig. I. a) varies in color from almost 
 while to Smoky yellow. The fore wings, which spread to ahoin l ; 
 inches, are darker than the hind, wings, and bear faint markings. 
 When at res! the wine- are held close to the body, forming an acute 
 triangle. The c«r<r hiving is done for the most pari either at night or 
 in the dusk of evening, the moths flying rapidly from plant to plant. 
 The male moth (lie'. 1. I> ) is usually somewhat darker in color than 
 the female and always -.mailer. 
 
 FOOD PLANTS. 
 
 Besides corn and sugar cane, this borer has been reported as feed- 
 ing on sorghum, Johnson grass, guinea corn, and grama grass. The 
 injury to the four last-mentioned plant- is never severe, but in plan- 
 ning methods of control they must be considered and an examination 
 mad.' to determine whether or not they are harboring the pest. 
 
 \ ATI i; w. ( iin KS. 
 
 The larger corn stalk-borer has very few natural enemies. A 
 minute Ilynicnopterous parasite i I richogramma pretiosa Rilej ) has 
 in a very few instances been found living in and destroying the eggs. 
 In one case ten of these minute parasites were reared from two eggs. 
 The larva of a In-own. velvety beetle {Chauliognathm pennsylvanicus 
 DeG.) sometimes enter- the hole- in the stalks of stubble after the 
 corn i- cut and devours the caterpillars found therein. This larva 
 has been found to be <d' greal value in reducing the numbers of the 
 borers in fields of sugar cane. The termite- or white ants (Termes 
 jinr'/p, Koll.i. locally known a- "wood lice," have been observed 
 destroying the larvae in the stubble in the winter, although apparently 
 only when the presence of the larvse interfered with the work of the 
 ants. In a few cases bodies of the borers have been found in the 
 stubble killed by a fungus, as yet undetermined, which envelops their 
 bodies in a white mold. Fungi, however, are too dependent on 
 weather conditions to be of any practical value in controlling the pest. 
 
 PREVENTIVE Ml V.S1 RES. 
 
 Rotation is one of the best general preventives of injury from in- 
 sects affecting field crop-. Experience has shown that win re corn 
 has followed itself upon the same field for two or more years there 
 has been a much greater loss from the borer than where an annual 
 change of crop has been practiced. This i- especially noticeable 
 
 [Cir. l L6] 
 
8 
 
 ■where stalks or stubble from the previous year have been allowed to 
 remain undisturbed throughout the winter. The moths, upon emer- 
 gence in the spring, finding themselves surrounded by tbe young 
 corn, commence egg laying at once and escape the clangers encountered 
 in searching for another field of corn. A forced journey in search of 
 young corn results in many of the females being eaten by birds or 
 being destroyed because of rain. cold, or failure to find the object of 
 their quest. A few moths will always succeed in their search, but the 
 successful proportion will be greatly decreased by persistent crop 
 rotation. 
 
 Another remedy, probably the best for this insect, is the thorough 
 destruction, some time before the period of emergence of the moths 
 in the spring, of all the stalks and stubble remaining in the field from 
 the preceding crop. If all this trash can be disposed of before the 
 opening of spring, the numbers of the pest must be greatly diminished 
 if not almost exterminated, for the only form in which the insect 
 passes the winter is that of the caterpillar, and the only known loca- 
 tion is in the lower tip of the corn root, snugly hidden. Some few 
 may, however, be found to survive in the roots of the larger grasses 
 mentioned above, and care should be taken in such cases to treat these 
 in the same way. The method employed in disposing of the stubble 
 and stalks will depend largely on the conditions in individual cases. 
 If the stubble is cut low and the land is moderately heavy, a 
 thorough deep plowing may suffice, an inch or two of well-settled soil 
 being sufficient to prevent the escape of the adult moths. Bringing 
 the stubble to the surface where it can dry will kill some of the con- 
 tained larva?, but this method depends too much on the state of the 
 weather to be trusted. By far the most effective plan is to remove 
 the stubble from the field with a rake and burn it. 
 
 In the cane field the methods of treatment must be adjusted to 
 correspond with the methods of handling that crop. The larvae com- 
 monly spend the winter in the trimmings and tops which have been 
 discarded at harvest time because of immaturity. This refuse, left 
 on the ground throughout the winter, becomes dry and inflammable 
 and, if thoroughly burned before spring, enough larva' will be killed 
 to insure at least temporary relief from the ravage- of the bore:". 
 
 Any method which will insure the complete destruction of the over- 
 wintering larva", if persisted in and carried out simultaneously over 
 large sections of the country, will effectually preclude serious damage 
 from the insect. 
 
 jImes Wilson, 1/vOlJlV 
 
 Secretary of Agriculture. 
 
 Washington, D. C, December 14, 1909. 
 
 [Cir. 116] 
 
 n 
 
 UNIVERSITY OF FLORIDA 
 
 3 1262 05252 3270