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Show DAMAGE TO CORN BY BORER ANY METHOD WHICH WILL INSURE COMPLETE DESTRUCTION OF THE OVERWINTERING OVER-WINTERING LARVAE, IF PERSISTED IN, WILL EFFECTUALLY PRECLUDE PRE-CLUDE SERIOUS DAMAGE FROM THIS INSECT. By GEORGE- G. AINSLEE. , 1 In many cornfioWu, especially in tho South, a heavy wind late in the season, before the corn Js matured, does great damage by breaking the plants off at the .Turface of the ground, thus ruining them. An examination of these broken stems will in most cases, show that they have boon greatly weakened by the burrows of a caterpillar known, as "the larger corn stalk borer. Its work is largely within the Btom of tho plant, and is so concealed that in most cases, unless weather conditions condi-tions make it conspicuous, tho presence pres-ence of the insect passes unnoticed. This insect seems to havo been originally an enemy of sugar pane and to have first transferred Its attontlon to corn in the southern part of this country, coun-try, where corn and cane ore grown over the same territory. It occurs in many countries whore sugar cane Is tho staple crop, and has caused great damage dam-age in the We3t Indies, British Guiana, Australia, and Java. Tho bulk of the evidence goes to show that it was first brought Into this country with the importation im-portation of sugar-cane cuttings from tho "West Indies and Central and South Amorica, where, Blnce early times, It has Interfered with the production of this staple Larger cornstalk ljorrr; Lnrvn in lower part of corn plant preparatory to hibernation. Corn is damaged oy these caterpillars caterpil-lars in two ways. First, in the early part of the season, while tho plants aro small, they work ln tho "throat" of the young corn, and If the tender growing tip and the protecting leaves Is once damaged all chances that the plant will become a normal productive specimen are gone. In many sections this Is commonly known as "bud-worm" injury, in-jury, 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" "bud-worm" damage may be charged to this Insect. The other form of serious dam a go chargeable to"-thls pest occurs later in this season. The larvae, having then left tho loaves and descended to th-e lower part of the stalk, tunnol in tho pith. If the larvae are at all numerous num-erous in the stalk, their burrows so weaken tho plant that any unusual strain will lay it low and doatroy all chanco of Its maturing. "Whno frequently fre-quently ten or moro larvae may Kvo and maturo ln one plant. It must be remembered that any infestation, however how-ever light, will lessen in some dogree tho vitality of the plant and cause a corresponding loss In the quality and quantity of the harvest. Immediately upon leaving the egg in spring tho young larva of the first generation, gen-eration, spinning a silken thread behind be-hind It, wanders down Into tho throat of tho plant as far as the water or dew usually standing there will allow it to go, and beginH to feed on tho leaves, going back and forth through the yet unfolded clusters and soon riddling the moro tendor leaves with aimloss burrows. bur-rows. If the burrow reaches the tender ten-der terminal bud where the future joints aro being formed, further growth at that point ceases and tho plant becomes stunted and misshapen, with no tassel. As the plant continues to mature, the larva "grows out," as PI Larger cornstalk borer, a. Snmmcr formed larva: h-c hibernating forms; d-c-f-g. Abdominal segments. the farmers say. It Is more likely that It Is the evidences of Its work and not the larva Itself that "grow out." but for whatever reason, tho caterpillar caterpil-lar soon leaves tho more leafy portion of the plant and attacks the stalk at or near tho ground. Here a holo Is cut through the outer wall th" stalk and I the larva burrows upward for a short distance, after which It seems to run aimlessly through the pith, frequently frequent-ly even leaving the stalk entirely and re-entering it at another point. a. I-'cmalc moth; b. V.'inga of male; c. Pupa. Turning upward, the caterpillar, when fully grown, bores toward tho outside and cuts a circular holo In the outer wall of the atalk. Thon, after spinning spin-ning a feW loos threads across this opening to kcop out undesirable visitors, visi-tors, it retreats a short distanoe, plugs tho borrow below with digested pith, and In the-chamber thus reatod slowly slow-ly changes to tho noxt or pupal stac. Seldom is the atalk damaged abev tho third joint from the ground, although al-though the larvae, when small, are found in the largo midrfbs of the lower leaves and lator in tho Beason, when the food supply is restricted, even in succulent nubbins farthor up. Thev somotimes also penetrate tho underground under-ground part of tho stalk In feeding and enter some of tho larger brace roots for a short distance. The larvoo of tho second generation work in a similar manner, except that at tho time they appear tho tassol haB been formed; hence tho damago Is now confined altogether to tho lower stalk. Thus, Instead of arranging to pass the pupal stage ln the upper stalk, thoy penetrate to the root to hibernato and there, as larvae, pass tho winter in a quiescent state. Rotation Is on of tho best general preventives of Injury from Jnracts affecting af-fecting field crops. Experience has shown that where corn has followod Itself upon the same field for two or moro years there has beeu a much greater loss from the borer than where an annual change of crop has been practiced. This is especially noticcablo whore, stalks or Btubble from the previous year have been allowed al-lowed to remain undisturbed throughout through-out tho winter. Tho moths, upon emergence ln the spring, finding thom- Itlutilntion of leaves of corn canscd by lnnac of larger cornstalk borer. selves surrounded by the young corn, commence egg laying at once and escape the dangers encountered ln searching for another field of corn. A forced Journey in search of young corn icsults ln many of the females bring ecten by birds orbelng destroyed ber cause 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. |