e nf SUjniip Jalanii atth limnin' tire plantations NUMBERED SERIES NO. 1 BULLETIN OF R. I. State Board of Agriculture John J. Dunn, Secretary THE ARMY WORM CLIFTON W. LOVELAND Assistant Entomolu^^w, , V' JUNE, 19d# y ^ 1940 K® , t V& "W PROVIDENCE: E. L. FREEMAN CO., STATE PRINTERS 1915 of lUfflite JtaLutb mb Jlnrotitettr? {Uattfotuma NUMBERED SERIES NO. 1 BULLETIN R. I. State Board of Agriculture John J. Dunn, Secretary THE ARMY WORM CLIFTON W. LOVELAND Assistant Entomologist JUNE, 1915 PROVIDENCE : E. L. FREEMAN CO., STATE PRINTERS 1915 THE LIBRARY OF THE jijrj 8 - 1C49 i' FOREWORD This bulletin is one of a number dealing with insects especially injurious to cultivated plants, which is being published by the entomological department of the State Board of Agriculture. These bulletins are made as brief and concise as possible and contain only information of value from a practical standpoint. This information is based on the latest data and observation obtainable. A. E. STENE, State Entomologist. THE ARMY WORM £3a.9 H© i 5 The Army Worm (. Leucania unipuncta) was present in Rhode Island during the summer of 1914, in far greater numbers than for many years It became a veritable pest in many sections of the state, causing damage to the extent of many thousands of dollars in oats, grass, millet, and corn. The insect was first observed on the grounds around the State House on July 15th by Mr. John J. Dunn, Secretary of the State Board of Agriculture. Soon after this date, reports of its presence came in hourly accompanied, usually, with requests for help to suppress it from doing further damage. The Entomologist and the Assistant Entomologist were kept very busy visiting infested farms and showing the owners ways and means of controlling this insect. The worst infestations were in the City of Providence, in Arlington, Knightsville, Lincoln, Middletown, and on Block Island. In these sections the Army Worm was present in countless numbers and did an enormous amount of damage in a few days. Whole fields of millet, rowen, and oats were despoiled before the owners knew of its presence. This was partly due to the fact that there had been no severe infestation of the Army Worm in a good many years, so that no special watch was kept for it, and partly to the habits of the worm itself. The Army Worm is always present in grass lands, though generally not in sufficient numbers to do conspicuous damage. Ordinarily, it acts in a manner similar to that of its near relative the cutworm in feeding at night and in hiding under ground during the day. Because of this fact, it may be readily overlooked although present in a field in goodly numbres. It is only in years of exceeding abundance, such as was the case during the summer of 1914, that it assumes the army habit of marching from field to field in its search for provender. 4 In most of the cases, the Army Worm had its start in old grass land which had not been turned over in several years. As small, almost black larvae (Fig. 5a) they fed on the lower leaves of the grass at first and later defoliated the entire field, giving it the appearance of suffer- ing from drought, although the month of July was moderately wet. Many farmers wondered why their rowen was apparently burning idp, but they did not investigate until the worms had started their 'march which was directed, in most instances, towards the corn crop. After once becoming established in corn, it is very difficult to find efficient means of control. Arsenate of lead as a spray is not practical there, as the lead is sure to collect in the sheath of the corn in sufficient amount to be harmful to cattle if the stalks are to be used as fodder. Experiments with hellebore demonstrated that, that insecticide is of .doubtful value after the larvae have become half grown as is usually 'the case when they attack corn. The larvae crawled down into the sheaths of the corn during the day (Fig. 1) to such an extent that nearly every sheath was full. Several farmers tried hand picking, but the following day they found the sheaths again occupied, although they had apparently protected the field thoroughly by furrows and postholes. Investigation disclosed that after the sheaths were filled with the worms, thousands of them found protection during the day in the ground at the base of the stalks from which position they emerged at night to climb up and devour the leaves. If there was room in the sheaths when day approached they found shelter there, but if not, they again found protection under ground. Over one hundred worms were frequently unearthed around a single hill of corn. The Assistant Entomologist made many visits in the evenings to the infested fields to study the habits of the insects. In the stillness of the night the gnawing of the immense number of insects was plainly audible. When the Army Worm invaded oats and millet its work, while fully as disastrous, was not so conspicuous as it was in the corn. It fed on the lower leaves first, later attacking the upper leaves and then Digitized by the Internet Archive in 2017 with funding from .b University of Illinois Urbana-Champaign Alternates cr https://archive.org/details/armywormOOrhod Fig. 1 . — Larvae of the Army Worm feeding on sweet corn. (Original.) 5 the head. In a few cases the head was eaten first. If the main body of the larvae did not w T ork on the outer part of the field, the whole crop would become despoiled before their work was noticed. Where these crops were attacked, the owners were advised to cut them at once and convert them into hay and at the same time to turn a double furrow around the field so that the insects could not invade other crops. In most cases there was not much of the crop to save, but the making of the furrows resulted in the destruction of hundred of thousands of the worms. One farmer who observed the worms at work in the early stages cut his oats, but was unable to cure the crop because of wet weather. When the oats were ready to haul in there was very little but stems left as the larvae fed on the prostrate crop. It "would probably be better in such cases to shake out the oats carefully and carry them to some other field to make. Indeed, this was done with millet on one farm in Lonsdale with entire success. In grass lands of considerable extent, the Army Worm spread out in all directions and reached maturity without acquiring the marching habit. Probably more harm is done under such conditions than when marching. Many a beautiful field of rowen was thus cut down to the stubble left by the mowing machine. In such fields, the larvse frequently assumed a vertical position on the shady side of the stubble in the daytime, As they were then two-thirds grown and had changed from a bla ckish color to one with alternate dark and light stripes, they were inconspicuous and one might pass through such field from end to end in bright sunlight without seeing them unless he were a close observer. In fact the writer had difficulty in making one farmer, who had appealed for help, see them although nearly every stubble had two of the larvse present in an upright position. If one walked across the field with the sun at his back not one could be seen. If one walked facing the sun the dark and light lines so blended in with the stubble that it was almost impossible to see the insects from an upright position. If one stooped over and looked across the field in a quartering position with relation to the sunlight, t he enormous number of the larvse became at once apparent. Burning 6 over such a field will result in the destruction of most of the insects as also will rolling it with a heavy land roller. DESCRIPTION OF THE ARMY WORM THE MOTH The moth of the Army Worm is shown in natural size in Fig. 7. It is of a dull brownish color with a white spot in the centre of each wing. There is a row of dark spots along the lower border of the wings and an irregular occurrence of dark lines running across the fore wings diagonally. THE LARVA The larvae are almost smooth, naked caterpillars, not worms, (Fig. 5). When they are hatched from the eggs they are a light brown color, but soon change to a greenish black. As they molt and grow, they acquire distinct longitudinal stripes and lines which extend the whole length of the body. Some of the stripes are greenish black, some are of a light straw color and some of the lines are white. When full grown the larvae are about one and one-half inches long. THE PUPA The pupa is of a light brown color when it is first made, but it gradually acquires a deep brown tinge. One is shown in natural size in Fig 7. The eggs are small globe-shaped bodies and are covered with a white secretion which becomes the first food of the newly hatched larvae. LIFE HISTORY The Army Worm belongs to the great group of Owlet Moths (. Noctuidce ) which includes the cutworms. It is generally supposed that the insect lives over the winter as a partly grown caterpillar, completing its growth in the early spring, pupating in April and coming forth in the moth stage about the first of May. Some moths are about before this date probably emerging from over-wintering pupae. Fig. 5. — Larvae of the Army Worm, natural size. (Original.) , young larva; b, partly grown larva; c, full grown larva; d, larva curled Fig. 7. — Moth and pupa of Army Worm, natural size. (Original.) 7 Some writers claim that they winter in all three stages, larval, pupal, and adult. The moths lay their eggs in the soil around grass roots or in the soil of weed infested borders of cultivated fields. The eggs hatch about the 15th of May in Rhode Island and become full grown in about a month. The larvae pupate about the middle of June and the adults emerge about July 1st. These mate almost at once, but they do not lay their eggs for four or five days. The resulting brood is the one which is the most numerous and which does the greatest amount of damage in Rhode Island. The larva? of this brood become full grown and go into the pupal stage about August 4th. The adults emerge from the pupae about the 20th of August. They were numerous around the street lights on Exchange Place, in Providence, on the 21st, 22nd and 23rd of August, and they invaded the Federal Building in such numbers that it was necessary to use the vacuum cleaner to get rid of their dead bodies. Some entomologists claim that a number of the pupae of the second brood remain under ground in that stage all winter, but persistent searching by the writer failed to disclose any pupae of this brood after the main flight occurred and furthermore moths emerged from everyone of several hundred pupae of this brood which were reared in the insectary. It is generally supposed that the moths which emerge about the 20th of August lay eggs which produce over-wintering larvae. This would complete the life cycle. This life cycle is true for the greater number of the insects, but individuals vary from it to such an extent that it is possible to find larvae of all sizes, pupae, and adults during any of the summer months, although not in sufficient numbers to make it necessary to take them into account from an economic standpoint. In 1914, at least, there was some important variations in the life cycle. The larvae of the third brood proved very numerous in some sections and the writer found them of all sizes on October 29th, on the Hervey Farm at Dugaway Hill. Some were feeding on oats, although there had been a severe frost on the two nights preceding. Many were curled up under ground, while some had pupated. As a great majority of the larvae were not over half grown it is reasonable 8 to suppose that they will live over the winter in that stage. That some of them reached the pupal stage is probably due to the abnor- mally warm weather obtaining during October which permitted them to feed much later than is usually the case. METHODS OF CONTROL As with other cutworms; the Army Worm can probably best be controlled by a proper rotation of crops and by clean cultivation. In the majority of cases the infestations have their origin in grass lands which have not been turned over in some years, or in weed- infested borders of fields. There was not a single instance of a first brodd infestation in fields which had received late fall or early spring plowing. If the worms were present in a neglected field during the previous year burning over early in May would result in the destruc- tion of most of the eggs which are laid previous to that time and plow- ing and harrowing would destroy such as survive the burning as well as the over-wintering larvae and pupae. During the first two weeks in July careful observations should be made frequently of grass lands and lands which have been planted with millet and oats. The importance of this cannot be over em- phasized. If the Army Worm is located when it first begins to work it is comparatively easy to take measures for keeping it within bounds. In making observations it will be necessary to look sharp, for the small, black larvae may be easily overlooked. The frass about the base of grass stems is an evidence that they are present and they may be disclosed, also, by shaking the growing grass or grain, for at the slightest disturbance they drop to the ground and curl up (Fig. 5d) . One ought to dig about the ground at the base of the stalks as they usually hide under the surface during the day and they may be found under any temporary shelter such as flat stones, pieces of paper, or clumps of matted grass. If it is found that they are present in any considerable numbers, a survey should be made to determine the extent of the land that is infested. Immediately after this is done, the crop should be cut and a deep furrow plowed around the Fig. 2. — A well made furrow and one which will act as a sufficient trap for the Army Worm. The stakes indicate the post holes for trapping the caterpillar. (Original.) Fig. 3. — A shallow insufficient furrow (Original.) 9 land infested, with the steep side away from the field and toward the crops to be protected. This furrow should be carefully made and whenever the side becomes broken down it should be straightened by the use of a spade. The loose dirt should be removed from the furrow and postholes a foot deep should be dug at distances of about a rod apart in the bottom of the furrow (Fig. 2). A double furrow will be found to be more efficient than a single one. The crop should be cured and removed from the field as soon as possible, taking care to shake out the larvae. They will generally fall to the ground at the least disturbance. With their food supply removed, the worms will attempt to leave the field in search of more and thus get into the furrow. They cannot climb the steep side of the furrow readily and will crawl along it seeking some easier means of egress, eventually falling into the postholes. Here they may be destroyed easily by spraying them with kerosene or by crushing them with a tamper. Do not cover them with soil to destroy them because those which are full grown will pupate and will later fly to lay more eggs for a future brood. This same method will also serve as an efficient means of control whenever the worms have started to march for any cause. In fact, furrows should be plowed with the steep side toward the crops to be protected whenever Army Worms are present anywhere in the neigh- borhood for they travel rapidly night and day until they find just the food which they desire. Too much stress cannot be given the matter of making a sufficient furrow. Shallow’, broken down furrows are valueless and yet the writer found many instances of such futile attempts to check the advance of the Army Worm in his visits to infested farms in 1914. See (Fig. 3). Whenever Army Worms are found on lawns or on grass which is not to be used as food for animals they can be destroyed easily by applying a spray, consisting of one pound of arsenate of lead to twelve gallons of water. If for any reason it is undesirable to use poison good results may be obtained by going over the ground with a land roller, especially if this is done in the evening. 10 The Army Worm seldom if ever gets its first start in corn, but if through neglect of taking the above mentioned precautions, it does get established there, it will generally be found, at first, that only part of the crop is infested. The farmer should at once examine the crop by looking into the sheaths, and by loosening up the soil around the roots, in order to determine how far the worm has advanced into the field. Almost always they work in from the side or end of the field first. (Fig. 4). Furrows as described above should be made at once separating that part of the field which is infested from that which is not. This will generally result in the saving of a greater part of the corn. If for any reason it is not desirable to make a furrow it would be well to sacrifice a half dozen rows of corn next to the infested rows and spray same with arsenate of lead. These rows should be carefully marked so that the stalks do not reach the stock as fodder. It will be necessary to do the spraying thoroughly and persistently as the nature of the corn leaves is such that the spray will not stick to them as readily as it does to the leaves of trees. If the greater part of the corn has become infested, the larvae can be handpicked from the sheaths and from under the soil around the base of the stalks. This is a rather slow and expensive method, but it can be made effective. An alternative measure would be to go through the corn in the daytime hitting each stalk a hard rap. This will dislodge many of the larvae which will find shelter under the surface of the ground until nightfall. Immediately after a small amount of poison bran mash may be scattered around the hills. It has been found by experiment that the larvae when coming out at night will eat the nearest food, which in this case would be the poi- soned bran, rather than to laboriously climb up the stalks to the leaves. This mash is made by mixing one pound of Paris green with 50 pounds of bran, stirring it up with diluted molasses and the juice of one-half dozen lemons or oranges until it has the consistency of stiff dough. In many western states where thousands of acres of corn sometimes becomes infested with the Army Worm the poisoned bran is scattered broadcast over the fields and a handful is thrown into Fig. 4. — Field of sweet corn, attacked on outside edge by the Army Worm. (Original.) FACULTY INITIAL S \ s SF 7 4 TENS 1 1 0 I SF 7 4 Z n / LOCATION units /if, PLEASE PRINT CALL NUMBER AUTHOR BRIEF TITLE SIGNATURE IDENTIFICATION NO. COLLEGE STATUS DATE DUE ( 0HH > B 77691 © UNIVERSITY OF ILLINOIS LIBRARY. URBANA ST VI LIN I AXinDVd > IH©J3a3SV SEMESTL rJ WEEK E | WEEK D | WEEK C | WEEK B | WEEK A 11 the curl of the corn. This method has been found almost one hundred per cent, efficient and can be employed at a cost of about twenty-five cents per acre. The poison bait is more effective when scattered in the early evening. One farmer turned his hens and chickens into a small field of oats wdfich was badly infested with the result that nearly every worm was devoured. In the West hogs are sometimes let loose to good purpose when the worms are numerous. The Army Worm moth is attracted to bright lights to a greater extent than is that of almost any other species. At times of their flight, millions may be destroyed before their eggs are laid, by sus- pending lanterns above receptacles containing water covered with a thin layer of kerosene and placed in infested fields. CROPS ATTACKED BY ARMY WORM The Army Worm confines its depredations as a rule to plants uf the grass family such as millet, oats, timothy, barley, herd ’s grass, wild grasses, and corn. It does not feed on the common garden vegetables, as many feared it would, when it infested their grass lands. Some truck gardeners went to considerable trouble to keep them out of crops of tomatoes, which they would not harm in any way. It seldom eats clover or, for that matter, anything else except such as those which have been enumerated so that the farmer need not take into account the ordinary vegetable crops when planning to circumvent the Army Worm. CAUSE OF INFESTATION OF 1914 Some of the most frequent questions asked during the summer of 1914 were “ Where does the Army Worm come from?” “Why is it so numerous this year? ” “ Will it be here in just as great numbers in 1915?” Perhaps no definite answers can be made to any of these questions. There are two factors which have some bearing on the relative number of Army Worms present in any particular year. 12 Probably the principal factor is the matter of parasites. If the parasites have been on the increase through a series of years so that their attack has reduced the number of Army Worms to a minimum, the parasites eventually will starve out and become almost extermi- nated. This condition gives such of the Army Worms as remain the opportunity to multiply. As the moth lays five or six hundred eggs it would not take very long for them to increase to immense numbers if there was no check of any kind placed upon them. The same thing would obtain if the parasites became destroyed through unfavorable weather conditions or by the abundance of secondary parasites. It is possible that the parasites of the Army Worm were scarce during the season of 1913-14 and thus the insect was enabled to increase to such tremendous numbers. Some entomologists believe that during a time of favorable winds enormous numbers of the moths are swept northward from states to the South. Experiments are now being carried on to determine whether or not this is so. It is highly probable that this is so for frequently, as happened on October 19th, 20th and 21st during the fall of 1914, an immense flight of a near relative of the Army Worm, the Cotton Moth, invaded Rhode Island. They were nearly as thick around the lights on Exchange Place as were the Army Worm Moths during the latter part of August and almost everybody mistook them for the moths of the Army Worm. As the Cotton Moth larvae feed only on the cotton plant it will be seen that the moths must have traveled great distances to reach Rhode Island. A study of the weather maps for October 16th, 17th, 18th and 19th, 1914, discloses the fact that a low pressure area passed up the Missis- sippi Valley and swung across New England. As the tendency of the air around a low pressure area is to move towards its centre the Cotton Moth probably had its journej^ directed and accelerated by this inflowing air. As there are five or six broods of Army Worms reared in the South every summer it is highly probable that it may frequently reach us in a similar manner and this may account in part for the infestation which visited us this year. Fig. 6. — Larva of Army Worm X5 with three eggs of a parasitic tachina fly attached to back. (Original.) 13 It would be impossible to predict as to the number of Army Worms which we may anticipate another year. It is seldom that they are numerous for two years in succession. A large number of them were parasitized during the latter part of the season and it is probable that the increase of these parasites will tend to hold them in check. Probably weather conditions will have much bearing on the number of these insects which may be present another year. ENEMIES OF ARMY WORMS Many birds are consistent feeders on the Army Worm. Large flocks of grackles were observed eating Army Worms in several sections. Red-wing blackbirds, robins, meadow-larks, cow birds, song sparrows, field sparrows, chipping sparrows, brown threshers, bob-whites, starlings, and even the much detested English sparrows devoured an immense number of the worms. One bob-white became so repleted with the insects that he was scarcely able to fly. One misguided farmer granted permission to some Italians to shoot the blackbirds which had gathered in immense numbers on his estate to feed on the worms which were destroying his corn. Whatever may be said in disparagement of the blackbird it is certain that no other bird does such yeoman service as he in ridding fields of this disastrous pest. There are some predaceous insects which feed on the Army Worm, notably the Digger wasp and both the larvae and adult of some Calosoma beetles. The most important enemy of the Army Worm is a parasitic tachina fly. This fly sticks her eggs on the back of the Army Worm near the neck (See Fig. 6) and the young maggot hatches and burrows into the host where its depredations encompasses the death of the worm. As this fly completes its life cycle in a few days, it increases so rapidly in numbers that in favorable seasons it is difficult to find a single worm of the third brood that has not been parasitized. During the week between July 15th and 22d, there were very few worms parasitized, but nearly all the worms seen after August 1st 14 had one or more eggs of this fly attached to their backs. The flies hovered over the postholes, dug in the furrows to trap the Army Worm, in large numbers and the result of their work ought to be apparent in 1915. The Army Worm is sometimes attacked by a fungus belonging to the genus Empusa which decimates their ranks to a great extent, especially in wet seasons. It is also subject to a bacterial disease commonly called the wilt disease since the caterpillar infected appears to be wilted. When this disease obtains a foothold it fre- quently wipes out whole armies of the worm. There seemed to be little of this disease present in 1914, and this may partially account for the severity of the infestation. &