U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— CIRCULAR No. 152. L. O. HOWARD. Entomologist and Chief of Bureau. THE RICE WATER-WEEVIL AND METHODS FOR ITS CONTROL. E. S. TUCKER, Entomological Assistant. WASHINGTON': GOVEIINMEN1 PRINTING OFFICE: BUREAU OF EXTOMOLOGY. L. O. Howard, Entomologist and Chief of Bureau. C. L. Marlatt. Entotnologist and Acting Chief in Absence of Chief. R. S. Clifton, Executive Assistant. W. F. Tastet. Chief Clerk. F. H. Chittenden, in charge of truck crop and stored product inst ct investigations. A. D. Hopkins, in charge of forest insect investigations. W. I>. Hunter, in charge of southern field crop insect investigations. V. M. Webster, in (lunge of cereal and forage insect investigations. A. L. Qitaintance, hi charge of deciduous [mil insect investigations. E. F. Phillips, in charge of bee culture. T>. M. Rogers, in charge of prev< nting spread of moths, fit Id work. Rolla I\ Currie, in charge of editorial work. Mabel Colcord. in charge of library. Southern Field Crop Insect Investigations. \Y. D. Hunter. in charge. W. D. Pierce, G. D. Smith, J. D. Mitchell, Harry Pinkus, B. R. Coad, R. "W. Moreland, engaged in cotton-boll weevil investigations. F. C. Bishopp, A. II. Jennings, H. P. Wood, W. V. King, engaged in tick investi- gations. A. C. Morgan, G. A. Runner, S. E. Crumb, D. C. I'arman, engaged in tobacco insect investigations. T. E. Holloway. E. R. P.ariser, engaged in sugar cam- insect investigations. E. A. McGregor, W. A. Thomas, < ngag< d in red spider and other cotton insect investigations. J. L. Webb, engaged in rice inset investigations. 11. A. Cooley, 1 >. L. Van Dine, A. F. Conbadi, C. C. Kbumbhaar, collaborators. ii Circular No. 152. United States Department of Agriculture, BUREAU OF ENTOMOLOGY. L. O. HOWARD, Entomologist and Chief of Bureau. THE KICK WATKIMVKKVIL AND METHODS FOR ITS CONTROL. i Lissorhoptrus simplex Say.) By E. S. Tuckj R, tomological Assistant. ECONOMIC 1 M PORTANCE. The most serious insect enemy of growing rice in the Southern States i- tlic rice water-weevil (Lissorhoptrus simplex Say) (fig. 1). When in its larval stage, the insect is known to rice growers as the ■• rice root-maggot/' The larvae feed on the roots of rice plants, and the adult weevils cause some harm by feeding on rice leave-. Owing to the extensive growing of rice in sections of Louisiana, Texas, and Arkansas within recent years, the weevil has found very favorable condition- in the rice fields for its multiplication in propor- tion to the increase of the acreage and to the number of year- in which rice ha- been grown in any section. The development of definite rice-growing areas in these States ha- naturally resulted in particular center- of high infestation by the weevil. Rice growing has consequently been attended by great damage to (he crop- on .e count of the insect's attacks. Tin amount of loss that is occasioned by the attacks i-. difficult to estimate, a- the reduction of yield has been variously reckoned in different localities. Since all fields are not affected alike and differ- ent portions or spots of a held are apt to suffer the severest injuries, although the plants seldom fail outright, the growers differ much in their opinion.- of ill- extent of damage which they sustain, hut all e in the declaration that it is considerable. General statements of the shortage of production include a report by a grower at Beau- :. Tex., who placed his loss a- low as 1 per cent : hut the attacks in '.me fields at Stuttgart, Ark., have been severe enough to cut down the yield a- much as 75 per cent. 1 THE KICK WATER-WEEVIL, Pig. I. -The rice water-weevil (Lissorhoptrua simplex) : a, Rice plant showing Injuries; h, larval scars on section of root: c, section of rootlet showing feeding scars: d, water line; e, c, c, roots severed by larva-; /, Injured leaf; /', enlarged section of injured leaf; y, adult beetle, dorsal view, much enlarged; h, antenna of beetle, more enls i, larva, side view, much enlarged ; /. enlarged segment of larva, lateral view ; k, dorsal structure of larva. (Original. I i ii i i RK i w \ i i i; w i t'.viL. 8 The recent work of the bureau on the rice water-weevi] was begun in L910 ly Mi-. ('. E. Hood, working under the direction of Mr. D. L. Van Dine. The present writer began work on the problem in 1911. In this circular many notes made by Mr. Hood arc incorporated. The object of this paper is to give as much practical information as is h<>\\ available about the weevil and measures for its control in order that rice growers may make proper efforts in fighting the pest and secure larger crops. The cooperative facilities afforded by the A.gricultural Experiment Station of Louisiana, through Prof. W. R, Dodson, director, in providing accommodations at the State Rice Station. Crowley, La., and allowing free use of the unpublished notes comprising a preliminary investigation of the rice water-weevi] by Mr. Wilmon Newell, in L909, deserve grateful acknowledgment. HISTORICAL ACCOT XT ANT) DISTRIBI TION. The weevil was originally described in ]<'<\ as Bagous simplex by Thomas Say. It and another species of weevil were given the generic name of Lissorhoptrus by Dr. J. L. LeConte in L876. Le- Conte and Horn have stated thai the weevil commonly inhabits swampy place- throughout the eastern part of the United States. Its northern range extends into the Lower Peninsula of Michigan, according to Hubbard and Schwarz, and Dury has recorded the spe- cie- as being taken near Cincinnati. Ohio. It is also reported from New Jersey, Maryland, and the District of Columbia. Mr. E. A. Schwarz has concluded " that t he genus Lissorhoptrus occurs all along the Atlantic coast (including the Gulf of Mexico), recur- along the Great Lakes, and i- occasionally found inland." A- an injurious insect, the species first attracted the attention of rice farmers along the Savannah River in Georgia and South Caro- lina. In 1881 Dr. L. (). Howard visited a rice plantation known as " Proctor's," and owned by ( ol. John Screven, on the South Carolina side of the river, a short distance below Savannah, Ga., for the pur- pose of studying the insects affecting rice crops. An account of his observations, including notes on the rice water-weevil, was published in the report of the United Stale- Commissioner of Agriculture for 1881 and 1882. But little advance has been made in further knowl- edge of rice-crop insects up to the present investigation. DESCRIPTIONS O] STAGES. The adult. — The mature insect is a small, dark-gray weevil i fig. 1, g). The technical description by Mr. E. A. Schwarz in the account above ment toned is here quot< d : Lissorhoptrus simplex.- [mago: Average length from tip of thorax, 3 mm. Oblong-oval, covered with large, dirt-colored scales, bul usually entirely en- 4 THE RICE WATEE-WEEVTL. veloped ill an argillaceous coating, which renders scales and sculpture irrecog- Dizable. Rostrum stout, as long as head and thorax, subeylindrical, densely rugosely punctulate, neither sulcate nor carinate; head densely punctulate. Thorax as long as wide, constricted anteriorly, lateral lobes well developed, sides moderately rounded, base truncate, a finely impressed median line, sur- face densely rugosely punctate, sides at middle with a shallow transverse im- pression. Elytra much wider at base than thorax and about twice as lung: humeri oblique, strongly declivous at apex, punctate-striate, interstices wide, subconvex, 3d and 5th more prominent at declivity than the rest. Presternum flattened, transversely impressed in front of coxae; abdomen coarsely punctate. Tibiae somewhat curved, armed with a strong terminal book; tarsi narrow. third joint not emarginate; claws slender, approximate. Very little difference exists between the sexes. The females usually have a slightly larger body than the males, and are often more dis- tinctly marked with a black area on the back. The marks of colora- tion, however, show more plainly on live moistened specimens in the field than on dry examples either alive or dead. According to Mr. W. D. Pierce, a secondary sexual character is presented by the con- figuration of the scrobe on the beak. He has determined that the scrobe of the female is slightly curved, but in the male it is practi- cally straight. These fine distinctions are difficult to make out with certainty on account of the natural curvature of the beak. The pupa. — No example of the pupa fit for description has yet been obtained, as it is very soft and any slight pressure or touch that is ex- erted in attempting to remove one from the mud crushes or distorts it. The egg. — All attempts to secure deposited eggs have afforded only partial results. For purposes of description dependence must at present be placed upon the appearance of eggs obtained by dissection of gravid female weevils. Mr. Wilmon Newell, in presenting a de- scription based upon such observations, has stated that the egg is pure white, cjdindrical and slightly curved in form, and has a length about five times the diameter. It is barely visible to the naked eye. LIFE HISTORY. SEMIAQTJATIC HABITS. Water is an element in which the weei il delights. It swims readily on or beneath the surface, and it feeds, rests, and mates almost as fre- quently in the water as above it. To determine how long the adults can live under water, Mr. C. E. Hood conducted a test in which one weevil died after passing the first 24 hours of submersion, but two did not die until after being kepi submerged for fully 96 hours. The weevil does not carry a bubble of air for breathing purposes when it goei below the surface, although tiny globules of air are apt to adhere to parts of the body. Without water, the insect can not breed. The eggs arc probably deposited on roots under water or in mud, and the THE RICE w A III: w EEVIL. larva, and doubtless also the pupa, require a bed of saturated earth in which to live. Wet conditions of soil with suitable vegetation a] to be ry for the development of all the stages. I OOD I'l Wlv The semiaquatic life of the insecl demands thai its proper food plants be adapted for growing in moist situations or entirely in water. The adult weevil itself is not disposed to feed on any plant unless the roots are at leasl partially covered with water or soft mud. In South Carolina Dr. Howard observed weevils feeding on " Sagit- taria. Scirpus, Cyperus, Nymphsea, and Nuphar" -plants commonly known as arrowhead, bulrush, galingale, water lily, and spatter-dock. Besides these, he reported wild rice (Zizarda aquatica) as well as cultivated rice (Orysa sativa). One specimen has been collected as a visitor on Baptisia at Victoria, Tex. All positive records of addi- tional food plant- refer entirely to grasses and they are the result of observations that were mostly made in Louisiana. Mr. Hood has re- ported some of the Louisiana grasses by the common name- of "bull grass" and "nigger's wool." which grew at Crowley. ••Hurrah grass" was recorded by Mr. D. L. Van Dine at Matagorda, Tex. Adult wee\ Lis U'^\ on the leaves of these undetermined grasses and the larva' were found on the root- of the first, winch was identified by the writer as a Paspalum ami was -aid to have been introduced into the count ry. " Bull grass '" is a very common term in the section and refers to several specii - of grasses. The occurrence of weevils on Walter's swale grass {Paspalum membranaceum) was first observed by Mr. Newell at Hake Arthur, La. "While similar observations have been made by the writer at Crowley. I. a., and Tine Bluff, Ark., the finding of larvae on the roots of the grass at ( 'row ley presented complete e\ idence of the true host relation-hip of the plant. This fact, however, may have been dis- covered ly Mr. Newel] two years previously at the same place where he found larvae infesting tie root- of a stocky Paspalum, which he was inclined to regard a- another species. Al-o during the season of 1911, at Crowley. La., the writer found two other species of grass which attracted the weevils from the nearest rice plant-. One of these was Bermuda grass (Capriola dactylon). It grew on a levee in a rice field which had become partly overflowed with the flood water. A- an attempt hail been made to grow it on the land previous to the rice crop, it- occurrence under •flooded condition- was exceptional, and no larva? were found attack- ing the root,. It can not lie considered a- a proper host plant. In the other case, a hunch of " water crab grass," undoubtedly a species of Syntherisina. was making a desperate struggle for existence 6 THE RICE WATER-WEEVIL. within a flooded rice field. Having evidently started into growth before the field became irrigated, this crab grass was able to live in a depth of about C inches of water. Xot only were the leaves severely fed upon by weevils, but the roots were attacked by larvae. APPEARANCE OF ADULTS IN RICE FIELDS. Since the growing of rice offers special inducements for the breeding of the weevil, clue to the attraction of the plants and the wet condi- tions which they demand for growth, rice has become the favorite food plant of the insect. Directly after the rice fields are flooded the weevils appear and commence feeding on the leaves of the young plants. In southern Louisiana, where much of the water is supplied by canals, the irrigation of rice fields usually begins in the first week of May, but the time of turning on water in different fields is often later, the flooding sometimes not being clone until in July to accord with late planting. "Where water is pumped onto the fields : a steady flow must be maintained for several clays before any large area of land can be inundated. The flooding of fields in Arkansas is not generally effected earlier than the middle of June. By following the application of water in every field the weevils gather most numerously on plants that stand in the depressions and lower portions having the deepest flood. Mr. Hood has counted as many as 18 weevils on a stool and 12 on a single plant. An average of at least 1 weevil to every 5 or G plants in one field has been reckoned by Mr. Newell. Some inclination to avoid direct sunlight during clays of hot weather is shown by the weevils, as they seem to prefer positions in the shade of the plants and under the surface of the water. They are rather sluggish except when swimming and are disposed to feign death if taken in the hand. They show no inclination to fly during the day and even refuse to expand the wings on being tossed into the air. Passage between separate plants is accomplished in the daytime by swimming. That they can fly for long distances, however, is clearly proven by their attraction to artificial lights at night. This propensity will be more fully discussed with reference to methods of control. Invasion of fields must therefore lie con- summated at night. NATURE OF ATTACKS BY AIM I I S. K'ice is attacked in the same manner as other similar host plants and the effects of the feeding by the adults are soon manifested by the appearance of scars on the leaves. (Fig. 1, /.) In the act of feed- ing, the weevil braces its body firmly on the upper side of a leaf, and moving slowly forward in a longitudinal direction either up or down the blade, it chews out the epidermis and produces a scar, leaving THE RICE w \ I I i; w EEVIL. / the underside uneaten. These scars are very narrow, being in fact no wi.lri- than the spread of the mandibles, but they vary in length from a small fraction of an inch to more than -J inches, depending on the lime in which the insect engages in feeding. When the thin un.lri--i.lr dries within the -car. it splits and forms an open groove throughout the injured space. The leaves suffer no serious ill effects from being fed upon unless the scars become numerous enough Lo cause wilting and dying. A.dults prefer tender young plants rather than the coarser strong growth. \i \ 1 1 ng \m> ovrrosn ion. Throughoul the period in which the weevils remain in evidence, mating take- plan- on nearly all occasions when a male and female happen to meet, and this usually occurs on a leal'. The gravid females crawl down the stems of the plants and evidently deposit their eggs singly in a puncture that i< first gnawed in a root. Mr. Newell ha- mentioned that he has seen adult weevils which he be- lieved to be females make punctures on the stems below the water line. Mr. Hood and the writer have watched the operations of lies when they apparently undertook to oviposit on rice roots within glass tubes. Each weevil thus observed deliberately sought out a place on a root anil ate into it for about a minute. Then she reversed her body, gripped tightly, and pressed the tip of the i men over the hole which she had eaten out. Mr. Hood has recorded that he saw the ovipositor in the form of a brown tubular organ in- serted into the hole. In this case the weevil remained in position without any apparent movement for 50 seconds before the ovipositor w.i- withdrawn. The writer ha- not been able to -re the ovipositor extended nor t.. detect an egg with certainty. The weevil may climb up above the water after each operation and rest for a long or shorl I. ..i- continue her actions among the root- for a while. One weevil stayed among the root- for I". minutes. The de\ ice that was designed and u-ed by the writer for observing the method of oviposition by the weevils is illustrated in figure 2. In it- construction a long lamp chimney was placed upright in a saucer and cemented at the base with plaster of Paris. A wire sup- port with the top bent into a loop of the proper size for steadying a closed-bottom glass tube, one with an inch diameter being used to hold the tool- of a young rice plant in water, was first placed in the center of the saucer. The lower end of the support was also bent in iral to secure firmness after being set in the plaster. By means of a string tied to tli, upper part of the tube, it could be lowered through the top of the chimney into a standing position within the wire loop and also removed to permit close inspection of roots and insects inside of it whenever desired. I 'ir. In2 12 2 8 THE RICE WATER-WEEVIL, NATURE OF ATTACKS BY LARV.E. "Sir. Hood has stated that the larvae are first found in the rice fields from one to three weeks after the turning on of the water, the time of their inception varying with the weather. Hot weather accelerates their development. The young larva?, which have doubtless hatched from egg- laid in the roots, begin to feed on them, and in course of time as the larvae increase in size they devour or sever large portions of the root system. They have been known to eat holes in large rice roots and burrow into them. Mr. W. D. Pierce, at Beaumont, Tex., in 1904, found vigorous larva 1 consuming the entire in- terior of the roots. Figure 1. '. gives a representation of Q ix feeding holes made at a distance not more than one-fourth of an inch apart as Mr. Hood viewed them. The common methods of attack result in a pruning of the roots, after which the severed portions rot and the remaining parts are further marred with feeding -ear-. At this stage the hold of the plant upon the soil is greatly weakened and it can be pulled from the ground with ea-e. In some instances on rec- ord the root systems were en- tirely destroyed and the rice plants floated in the water. The injuries done by the larva; first cause the leaves of the rice plants to turn a pale yellow and droop, the lower blades often re-ting on the water. With severe attacks some of the leaves may die. These effects in the fields become most pronounced on plants growing in depressions and low portions of the land into which tin' water first flowed and where it Fn;. 2. — Lamp-chimney case for rearing and observing the rice water-weevil: n, <;ia-s lamp chimney ; '*. vessel containing plaster of Paris; <■. glass tube; . failed to dis- close any evidences of infestation :il the time. These results -how conclusively that the weevil docs not breed at this lime of year even in most favorable situations. Not only were the adults absent, but the hick of feeding scars on the leaves denoted that they had not visited there for some time. THE RICE w \ PER WEEVIL. 11 The fad thai adults live throughout the greater pari of the season has beer demonstrated several times. In an experiment with speci- mens collected at Mackay, Tex., April 5, L904, Mr. W. W. Yothers succeeded in keeping the weevils alive by furnishing grass for food until after the middle of duly. Weevils confined on rice plants by Mr. Hood at Crowley, La., duly IS. lived later than the middle of September, and the writer has made a corresponding record cover- ing a period from July 11 to September 21. The common absence if not scarcity of fresh signs of feeding by adult- late in the season or at the time when the new generation of weevils is expected to emerge throws much doubl on the question of their taking any food then. At least they do not remain long on the plants, and the few feeding -ear- that may appear to have originated at the time are likely produced by lingering adult- of the old gen- eration. A yearly overlapping of generations in the adult stage evi- dently occurs. Few specimens thai might be regarded as freshly emerged weevil- have been found in the fields. These were taken by Mr. I Iood. hiding in the cracks of the ground a fter the water had I ieen drained from the held for harvesting. Possibly some of these weevils stray to electric lights at night, my last capture of a weevil being made on the nighl of September 20. If a new generation of weevils occurs no evidence of it has been found. The question is. What be conies of them until they go into hibernation \ HIBERN eriON. 1 During the fall and water of 1910 Mr. Hood made examinations of various places which might serve as hibernating quarters. The materials examined included rice stubble, loose dirt in the held-. straw-tacks (both old and new), grass and other vegetable matter along le\ee-. ;:ud Spanish moss. No weevil- were found hibernating except in the Spanish moss, which, however, afforded an excellent shelter, as the following tabulated observations made at Crowley, La., will show : Observations on the places of hibernation of the rice water-weevil. Oct. 26.. Nov. 19. Dec.2... Date m' exam] Moss examined. 1 1) Distance nearest ground. Number of w eevils found. number of per ton 1.464 1 Wit i few remarks, all of the notes on hiberi the weevils must be credited t<> Mr. Hood, who has made the most extensive Investigate ■ IT mile). 12 THE RICE WATER-WEEVIL. As indicated by the preceding table, several thousand weevils may hibernate in the moss on a single tree. The appearance of large numbers of weevils in rice fields when they are first flooded has led to the opinion that the pest completes one generation on host plants other than rice before this time. But as already pointed out, no evidence has been secured that will sustain this view. Abundance of the weevils is probably due to their successful survival through the winter and emergence from hibernation. One reference in literature mentions the occurrence of adults " in wintertime under old leaves and other shelter in drier pla< es near the swamps." The finding of one adult in litter beneath rich stubble is recorded by Mr. D. L. Van Dine as the result of searching for half of a day at Stewart, Tex., on Octoher 28, 1909. Entrance into hiber- nation is probably not begun much before the time when the nights are cold enough for frost. Not a single weevil could be found by the writer in a collection of Spanish moss obtained on September 29, at Crowley, La., and in the preceding spring after the first weevils appeared Mr. Hood was unable to find any specimens remaining in the moss. NATURAL ENEMIES. Besides birds no enemy is known to feed on the mature weevils, although the snakes and frogs which frequent the fields probably do so. Bird droppings found by Mr. Hood in a rice field at Stutt- gart. Ark., on September 12 consisted largely of insect remains, those of the rice water-weevil being the most abundant. However, two perfect specimens of the weevil were removed from the droppings and one was found to be alive. According to records in the Biological Survey, this weevil is eaten by the long-billed marsh wren (Telma- todytes palustris) and the mallard duck (Anas platyrhynchos) . Owing to their concealment in mud the larva and pupa are secure from enemies. When infested roots are pulled for examination and larva' are washed out any minnows that happen to be present in the water will greedily snap the floating bodies. Predaceous larva? of v.atc; beetles, which also abound in flooded fields, struggle with one another for possession of a weevil larva. If these predators and the several kinds of rapacious water bugs were adapted for burrowing in the mud and reaching the rice roots, they would be very efficient oyers of both weevil larva? and pupae. But their habit of hunt- ing in the open -paces of water renders them of little or no service against the weevil. METHODS OF CONTROL. UK \l\l\i. 01 Till FIELDS. A- pointed out in the study of the life history, the existence oi the larva' and likewise the pupa' depends upon a saturation of the soil. I ill'. RICE WATER-WEEVIL. 13 If the soil dries out after the larvae have made an advance in growth, they soon die. Tin- practice of draining fields and allowing them to dry enough to cause the death of the larvae was first proposed in 1881 by Col. John Screven, a rice planter in South Carolina, and was indorsed by Dr. Howard after his investigation in the field in l v M. of the rice growers in Louisiana and Texas have reported good ts from periods of draining, while others have claimed that the plants suffered more from being deprived of water than from at- tacks. Many growers therefore advocate deep flooding of fields as proper treatment of rice when infested by the weevil larvae. Different results of draining are mainly accountable to the ex of damage done by the larva' at the time of releasing the water. When the roots have been hut slightly or not yet severely attacked, draining seems to result very effectively in most cases by the reduc- tion of the number of larvae to a minimum. Effectiveness depends on the length of time that plants can stand -without water and not suffer from the want of it. Plants that have a fair hold of roots show no ill effects of drying spells lasting from 5 to 10 days without rain. In case of heavy rain, drying should he carried on for some longer or until the. surface of the ground forms a dry crust and begins to crack. This f drying has been found very effective in causing the death of larva-, and the ground has still retained sufficient ■ -ire below the surface to sustain the plants that possessed a large proportion of root-. On the other hand, when roots have become severely pnmed. the plants are unable to endure draining without being further impaired. Instead, they need a plentiful supply of water in order that new roots can he put out and growth resumed. The value of draining is de- pendent upon the enforcement of the practice at the proper time, which the grower can easily determine by making examinatioi the roots. Many growers object to draining on account of the • of water and the risk or difficulty of getting fields promptly flooded again. If fields were so arranged that water could be turned from one to another in succession or from early to late plantings, most of the i >uld he utilized and the saving in the cost of pumping, where this mean- of supply is employed, would he an item of coi eration. Other benefits arising from change ter will be men- tioned later. Continuance of flooding to enabl< nine inpirv by larva-, instead of taking steps to destroy the . will. a- Mr. Newell has inferred, probably lead t<> a regular in the number of weevils until the point i- reached where, the ii will make profitable rice culture impossible. Coi loes not in the least inconvenience the Ian ondi- even more favorable for them. Being the most practical method of controlling the weevils, draining of field- .3 highly im- portant 14 THE EICE WATER-WEEVTL. RESULTS OF DRAINING. Conclusive observations upon tests of draining conducted by the writer or under his instructions during the season of 1911 are pre- sented in the following statements. At Crowley. La., en June 9, a rice grower drained some parts of his field of early planted Honduras rice in which fully one-fifth of the plants, then at a height of 15 to Is inches^ showed yellow blades. The roots had been rather severely pruned, but enough remained together with newly grown ones to permit draining with safetv. As many as six and seven larva? infested the roots of a stool. Reflood- ing was effected June 19, after a period of drying which had lasted nearly 10 days. Quite a noticeable difference existed between the drained and undrained rice on July 21. The plants in the drained areas had nearly all headed out uniformly, while most of the un- drained rice was behind in growth, either not having headed or hav- ing heads just formed and blooming. Regarding recovery, the ownei said that the plants which grew in the fresh water after reflooding soon lost their yellow color and took on a vigorous growth of healthy green, but in the undrained parts with standing water the plants re- covered much more slowly. At harvest time the owner estimated his best yield on land that had been drained to check the weevil larvae. In the field of another grower, however, results were not so suc- cessful. These small young plants were not injured badly and showed only incipient spots and streaks of weak yellow color. This was a variety of Japan rice. The field was drained May 29 and re- flooded June 8, giving a drying of 10 days. One week after reflood- ing the plants had taken on a fresh green color, and the infestation of the most injured roots had been reduced to a minimum, as shown by the nearly normal growth. Owing evidently to a second infesta- tion, during which no draining was done, an irregular belated growth was displayed at heading time. Whether the outcome might have been worse without any draining can only be surmised. Acting under a cooperative agreement. Mr. C. G. Haskell reported some very important results of his examinations at Almyra. Ark. On draining a. field July 20 In- found 25 larva' on the roots of 25 sfools. On flooding the field July 28 he found only two larvae on the same number of roots. The result was accomplished by eight days ^<( draining and drying. A stool usually produced live stalks or stems. By calculating percentage- of infestation according to the number of stalks the draining must have reduced the proportion of larva' from 20 pel- cent to L.6 per cent. Again, on draining a field July 25 Mr. Haskell found 50 larvae on the roots of 25 stools, hut on reflooding the field July 31 he found no more than 9 larva' per 25 stools. The draining and drying therefore I II I. RICE W A I EB WEEVIL. 15 lasted six days, and calculating on ;i brsis of five stalks to a stool the tation was reduced from 10 to 7.2 ] >•■ r cent. The writer's own examination of this rice on August I. the second day of refiooding, gave substantial evidence of the reduction of larvae in corresponding numbers, the count resulting in 3 larvae on the roots of 10 stalks. Ai Pine Bluff, Ark., on August 5 the writer made examinations in a rice field that had been drained for five days. On the roots of I", stalks only nine larvae were found alive. The infestation there- fore amounted to approximately 9 per cent. The owner stated that before draining two and three larva? occurred on a -tool. Calculating five stalks per stool, the infestation then could nol have been less than 33 per cent. In sonic places the ground was still saturated, but most of it was stiff mud. Thai the draining really caused a reduction in the number of larvae by death was evidenced by the finding of two dead ones, and some of the live ones seemed weak as if about ready to die. Not many roots were badly cut and the draining began at an opi portune time. The pumping of water on this Held was resumed August 8, but ii was not wholly Hooded until a few days later. The drying covered seven days at least. No rain fell during this time, and the ground had begun to crack from drying. The results were considered very beneficial, as the larvae caused no further trouble and the rice headed out splendidly. EFFECTS in RUNNING WATEE. Direct observations, as well as the testimony of growers, I brought out the fact that rice growing in running water suffers little from weevil attack-. In these cases, however, no considerable area ha- yet he. mi -ecu in which the water flowed with any perceptible cur- rent. To maintain a distinct moving Hood over a large field would require an immense supply of water. The instance- that have been observed were confined i" -pot- or -mall plat- covered by the inflow of water from ;i canal or ditch. In spreading onto a Held from an inlet the current soon loses fop-,, and any low temperature. Where ;i cool How of water i- pumped from a well directly onto a Held the low temperature seems to exert n controlling factor against infesta- ticn. But these cases arc rare, because the rice demands warm tem- peratures for vigorous growth, and the -un heat greatly restricts the 1 area. EFFECTS 01 DEEP IND SHALLOW I NO AND STAGNATION. Deep water ami stagnant water greatly favor development weevil-. A- already pointed out, rice in -pot- or areas of deep ing i- most severely attacked. Severity of attacks i- especially 16 CHE RICE WATER-WEEVIL. marked in shallow water almost as much as in deep water when either heroines stagnant. In a field that had received only a scant supply of water, which in fact merely filled the low places although keeping all of the ground soaked, very few larva' could be found. Most of these larva? occurred on roots of weak plants in the pools, while the best growth stood out of water and was scarcely attacked at all. Soaking instead of flooding appeared to result very bene- ficially, not only controlling infestation but inducing prime growth of plants at least past the stage "of stooling when the coarse leaves offer little attraction to the weevils. EFFECTS OF EARLY, DELAYED, AND LATE FLOODIMi. Rice in different fields that were first flooded at various times covering a seasonal range of dates in accordance with the planting and sprouting has in due course been found subjected to the same degree of infestation. No advantage can he gained against the weevil by choosing any particular time for flooding that will still be suit- able for the needs of the plants. An attempt to delay full flooding by a gradual soaking of fields in order that the plants might attain a strong growth and be able to withstand or escape attacks after deep water was applied met with interference from heavy rainfalls which flooded the fields, and the owner then saved the water. The probable effectiveness of soaking is indicated by the case of accidental shortage of water, as mentioned in the preceding subject. EFFECTS OF ALTERNATE FLOODING AM) DRYING. At Crowley, La., on June 28, inspection was made of a field of rice that had been allowed to dry out from stoppage of water supply on two occasions, one lasting six days and the other four days. The oc- currence of larvae was limited principally to the most heavily flooded parts, and the roots of the plants were not badly injured. The com- parative scarcity of the larvae throughout the field was attributed to the effects of the two intervals of drying, and the rice escaped much danger from attacks. At Almyra. Ark., on August 1. other observations were made on a field where scarcity of water had caused alternate periods of drying. Water had been supplied but little more than half of the time since first Hooding, though the ground had been generally kept damp with the addition of rainfall. No larvae were found on the roots of this rice, and Only a few weevils occurred on weak plants near 1 he edges of the field. The plants exhibited a high, vigorous, and fairly healthy growth, the laclc of enough water having evidently resulted in a yellow tinge of the leaves, which, however, promised to be BK i w \ I i i: w EEVTL. 17 speedily overcome owing to flooding rains. The crop eventually produced an excellent yield. 1M (H FERTILIZERS \NI> APPLICATION OF LIME. In an experiment to determine whether the use of fertilizers and application of lime would serve as a check on weevil infestation, plats for growing rice were prepared at Crowley. La., as shown by the accompanying diagram, which also gives the results of examinations on July 8. The whole field was flooded equally to an average depth of G inches. The arrangement and treatment of the plat- and status of infestation are outline. I as follow-: Unlimed. Unlimcd. Limed. 2.000 iiounils [.or acre. Checks ;> larva -'alks. 1 larva. 11 la: Acid pi inds, 10 per 7 larva :alks. C larva . Acid phosphate m< above i>lus muriate oi potash, 60 pounds per acre 11 larvi -:alks. 9 larva-. 7 lar Total proportionate number of larvae: For the cheek plat 17. or 22jj per cent infestation. For the phosphate plat 19, or l'.v. per ceul infestation. For the phosphate and potash plal 30, or 10 per cent infestation. Calculating another way from the foregoing outline, the limed areas were found to have ■_'! larvae compared with 1G larva' in the unlimed areas of the same plat, while in the opposite plat 26 larvae were taken on the roots of < be same number of sta Iks. No advantage in reducing or retarding infestation appeared to be shown through the application of fertilizer- or lime to the soil, bul rather the contrary effects are indicated, as the strip with double fertilization contained the mosl larvae. Since the plant growth had responded in proportion to the d< : fertilization, the stimulated plants exhibited uo signs of injury resulting in yellow appearance of Leaves except in the limed areas, which a> a whole included the poorest growth on account of the severer pruning of the small root systems. Further observations made at Midland. La., have led to the con- clusion that fertilization doc- uot prevent nor even hinder the pro- pagation of larvae, but the extra nourishment may assist the plants to overcome attacks. 18 THE BICE WATER-WEEVIL. USE OF TRAP LIGHTS FOR ADULTS. The appearance of adults at artificial lights at night has suggested the plan of placing lights in the fields and trapping the weevils which may be attracted. Great numbers of the weevils seek the electric lights of stores in the towns throughout regions where the insects abound. ( )rdinary lights in dwellings are sometimes frequented. At Crowley. La., more than a hundred weevils have been collected within a few minutes on a single store window. They appear most numerously on warm dark nights, but, like many other insects, they do not fly to lights in any considerable number when the moon shines. Neither does the time of their flight seem to last long, for as soon as dark- ness has settled, most of them come in a rush, and only occasionally do stragglers show themselves later in the night. Their seasonal appearance begins from the 1st to the middle of April, and about the middle of August they become very scarce. Tests of the efficiency of light as a practical means of attraction were conducted at Crowley. A portable acetylene outfit was used to furnish light, being operated near rice fields 1 mile from town. Some of the best results were as follows, the weevils being taken on a cloth screen that was provided for the purpose of inducing them to alight : On the night of May 26, 1910, Mr. Van Dine started the light at 8 o'clock and captured over 40 weevils in the first 15 minutes. Later the breeze increased and only strong flying insects came to the light. Starting the light at 8 o'clock on July 19, after a day of heavy rains. Mr. Hood collected - 1 weevils in 45 minutes. But on the night of July 29, which was clear and warm with slight south breeze, be placed the light in the middle of a rice field and caught 12.") weevils between 8 and 9 o'clock. SUGGESTIONS FOB PROTECTIVE TREATMENT. POISON'I.M, ADULTS. When the weevils gather in particular portions of a rice field, as they often do along deeply flooded edges, dead furrows, and in spots, opportunities seem to be presented whereby the application of a food poison could be made. effective. As the weevils indulge in rather ex- tensive feeding compared with their size, the poisoning of the plants would be apt to cause the death of great numbers of the adults that might feed upon the poisoned leaves. The application of the poison should be made upon the first appearance of the insects before they have had much chance to oviposit. The poison must be selected with reference to its safety on the plants, and if in the form of a powder, it could be easily distributed by means of a dust gun. from I in BK i w \ i t t; w EE\ l!,. 19 which it mighl be spread for some distance by wind. Probably the only danger would be to live stock having access to the water the drinking of which would be a remote possibility. i I I 1 I i: \1 MANAGEMENT. Clean cultural management in dealing with the weevil as with other crop pests is advisable. By restricting the growth of the various grasses and other plant-, particularly the objectionable red variety of rice, which grow along and within canals, ditches, and water boles, much advantage could be derived toward the suppression of the breeding of the weevils on the uncultivated host plants. Drain- age of bayous, sinks, and water hole- would doubtless be of great benefit for the control of the weevil alone. Leveling of the surface of fields that are to be planted in rice and plow ing in such a manner as to avoid dead furrows as much as | hie would obviate many of the depressions which on being deeply flooded conduce to a high infestation of the plants in such place-. Finally, a thorough preparation of the -oil before planting is to he recommended, in order that grass and weed- ma\ he eradicated with- out the necessity of deep flooding for the purpose of drowning them. Thi.- will permit very -hallow flooding with periods of draining or mere soaking of fields for the control of infestation and the better- ment of the crops. -I M M \KY. The rice water-weevil causes more damage to rice crops in the Southern State- than any other insect affecting rice plant-. When it is in the larva] stage it commit- severe injuries to rice plant- by de stroying the root-. Some harm i- done by the adult- in feeding on the leaves. The insect chooses food plants that grow in wet places and it breeds only where it finds water. Eggs are evidentlj laid on root- in water or mud. under which condition- tin' larvae hatch, feed, grow, and transform into pupae, and finally the adult- mature and emerge. Two generations may possibly be produced in a season, hut one generation seems to he the rule. Adults pas- the winter in hiberna- tion, appearing in spring and invading the rice held-. The most practical means of controlling the weevil consists in the practice of draining and allowing infested rice fields to dry suffi- ciently at tic propel- time or before the attacks of larvae have greatly weakened the plants. Alternate flooding and drying, if carried out properly, will accomplish the same results. Very -hallow flooding or soaking of fields re-train- infestation. Fertilization assists the plants to overcome injury. 20 THE RICE WATER-WEEVIL. Considerable numbers of weevils can be captured at lights and destroyed, and the possibility of poisoning them in fields needs to be put to the test. Cultural management should be directed with the view of enforcing every advantage against the weevil that will be consistent with the welfare of the crop. Approved: James Wilson, Secretary of Agrit uZture, Washington, D. C, April 12, 1912. ADDITIONAL COPIES of this publication -Ti- may be procured from the Superintend- ent of Documents, Government Printing Office, Washington, D. C, at 5 cents per copy UNIVERSITY OF FLORIDA lllllIIISIIIIIIIIIIE.il 3 1262 09216 5652