^ op ued June 10 U. S. DKIWRTMKXT OF AGRICULTURE, BUREAU OF ENTOMOLOGY CIRCULAR No. 123. L. O. HOWARD. Enlomologisl and Chief of Bureau. METHODS OF CONTROLLING TOBACCO [NSECTS. A. ('. MORGAN, Agent mn/ Expert. 1(17(11 — 10 1 WASHINGTON : GOVERNMENT PRINTING OFFICE : 1B10 BUREAU OF ENTOMOLOGY. L. 0. Howard, Entomologist and Chief of Bureau. C. L. Marlatt, Assistant Entomologist 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 insect i /instigations. A. D. Hopkins, in charge of forest insect investigations. W. D. Hunter, in charge of southern field crop insect investigations. F. M. Webster, in charge of cereal and forage, insect investigations. A. L. Quaintance, in charge of deciduous fruit insect investigations. E. F. Phillips, in charge of bee culture. D. M. Rogers, in charge of preventing spread of moths, field work. Rolla P. Currik, in charge of editorial work. Mabel Colcord, librarian. Southern Field Crop Insect Investigations. \V. D. Hunter, in charge. W. D. Pierce, R. A. Cushman, C. E. Hood, E. S. Tucker, George D. Smith, \V. A. Thomas, T. E. Holloway, George W. Hood, V. I. Safro, Harry Pinkus, engaged in cotton boll weevil investigations. F. C. Pishopp, J. D. Mitchell, H. P. Wood, R. A. Cooley, W. V. King, engaged in cattle tick life history investigations. A. C. Morgan, G. A. Runner, S. E. Crumb, engagedin tobacco insect investigations. I ). L. Van Dine, engaged in sugar cane and rice insect investigations. F. C. Pratt, engagedin cactus insect investigations. Wilmon Newell, T. C. Barber, engagedin Argentine ant investigations. ii Circular No. 123. Issued June 10, 1910. United States Department of Agriculture, BUREAU OF ENTOMOLOGY. L. O. HOWARD, Entomologist and Chief of Bureau. METHODS OF CONTROLLING TOBACCO INSECTS. Bj A C Morgan, .|i/. nl and Expi rt. INTRODUCTION. [investigation by the Bureau of Entomology of the United States Departmenl of Agriculture of insects affecting tobacco has been in progress in the "dark tobacco" districts of Kentucky and Tennessee since Jubj . I 907. In the work in Tennessee the Bureau of Entomologj has had (lie heartj cooperation of the Ten- nessee agricultural experiment station and of its director, Prof. II. A. Morgan. During the sum- mers of 1908 and 1909 Professor Morgan assigned a student, Mr. I). ('. Parman, of the University of Tennessee, a- an assistant to the Federal agenl in charge of the tobacco-inseel investigations. The writer wishes to express his thank- to Professor Morgan for t lie persona] advice received from him and for this valuable COOpera- Fio.l. -Agrotis ypsilon, one of the tobacco cut- jj ( ,ll worms: n. Larva; '<. head of same; c, adult. . . ,, • Natural size. (From Howard.) In tin- investigation all in- sects found affecting tobacco have Keen studied, hut particular attention has been given to the differenl species of cutworms, to the tobacco flea-beetle (Epitrix parvula Fab.), and to the tobacco hornworms [PldegetTiontius sexta Joh. and /'. quinqu* maculata Haw.). In this particular circular only the insects mentioned above are considered. Although the investigation has not been completed, METHODS OF COX TROLLING TOBACCO INSECTS. it is thought thai a description of remedies already in use, with the addition of those discovered during the investigation, may be of value to the growers. It should be stated that the remedies herein treated will apply not only to Kentucky and Tennessee, but should apply equally as well to all tobacco-growing States which do not border on the Gulf. CUTWORMS. Tobacco is frequently very seriously injured by various species of cutworms, of which two common species are illustrated in figures 1 and 2. It is the common experi- ence of all farm- ers that cut- worms are the most abundant and injurious on land that has been left uncul- tivated for some t iine previous to being planted to a certain crop. Where tobacco follows clover serious injury from these pests is likely to re- sult. On the other hand, if winter grain pre- cedes tobacco very little injury is likely to occur. However, if tobacco is to follow a clover sod it is a simple matter to rid the soil of these "worms." I f it is possible to do so, the sod should he plowed under in the fall or winter and he kept free of vegetation by disking orharrowing. Thus by keeping the held free of vegetation the cutworms will be starved to death before the time for setting the tobacco. When sod land is plowed only a short- time before setting the tobacco, a trap bait may be used to rid the field of the worms. In banners' Bulletin .No. I20 a Dr. L. O. Howard recommends thoroughly spraying a patch of weeds or clover with Paris green-, then cutting it and dropping it in little bunches here and there throughout the held. Another trap bait that meets with wide favor is also recommended by Doctor Howard.'' It Fig. 2. — A tobacco cutworm (Pcridroma margaritosa): \ the common names of "tobacco Ilea" and "flea-beetle." It max be found, from setting time until frost, in more or less injurious numbers in evevy tobacco held in the I 'nitcd States. The most injurious outbreak on record occurred in the ''dark Fio. 3. Tin' tobacco flea-beetle l Epitrix parmla): a, Adult beetle; b, larva, side view; c, head of larva; (/.hind legot same; < . anal segment of same; /. pupa. «. b, i . Enlarged about 15 time more enlarged, i From Chittenden.) tobacco distric of Kentucky and Tennessee in the spring of 1907. Nearly all plant beds, except those tightly canvased, were devastated. Practically all the first sowing was destroyed and in many cases the second and third also. I n consequence t he acreage \\ as reduced 1 ."> to '20 per cent . and owing to the fact that the crop as a whole was set much later than Usual an additional loss resulted. Late-set tobacco docs not produce the same number of pounds as the early-set tobacco, and because of l he lateness of harvesting and t he near approach of cool w i 'at her this tobacco frequently cures poorly and is graded lower than tobacco that is harvested earlier in the season. The loss in Kentucky and Tennessee in 1907 was not far from $2,000, - The tobacco flea-beetle passes the winter in the adult stage in piles of dead leaves or dead grass in the woods, or in fence corners and 4 METHODS OF CONTROLLING TOBACCO INSECTS. similar localities. The beetles begin to emerge from hibernation in Kentucky and Tennessee in March, generally about the time the young tobacco plants are appearing in the plant beds. The young and tender plants furnish a favorite food for the beetles, and unless the beds are well protected by canvas considerable damage is sure to result. The flea-beetle also seriously injures tobacco in the field. The writer has observed fields where numbers of plants were killed by its ravage-. The young leaves were riddled with holes (fig. 4 I and new foliage was completely devoured as fast as it appeared. The tobacco flea-beetle occurs upon many species of solanaceous plants, as it has been found feeding upon tomato, potato, horse nettle, ground cherry, and "jiinson weed'' (Datura stramonium). It lays its eggs on or near the base of the stems of these plants and also upon the stems of young tobacco plants. The principal injury to tobacco is occasioned by the feeding of the adults upon the foliage, although Fig. -4. — Leaf of young tobacco plant, showing work of the tobacco flea-beetle. (Original.) the larvae occasionally do considerable damage to the young plants by feeding upon the roots and stems." PREVENTIVE M EASURES. Properly canvased beds escaped uninjured in 1907. Only whole, strong canvas should be u>ed, with boards or straight logs for the sides of the bed, banking up the earth 3 or 4 inches againsl the sides so that no holes are left beneath the logs, and fastening the canvas closely and securely to the sides. Beds canvased in this way will not suffer from flea-beetle attack. " The biology of this insect has been carefully worked out by Dr. F. II. ( hittendeD in Bulletin No. 10, of this office, pp. 79 82, and in Bulletin No. 19, pp. 85 87. Ml CHODS I IF CON l ROLLING rOBACCO [NSECTS. REMED1 VI. MEAS1 IM - Even though flea-beetles do gain access to the planl beds in greal numbers the} can be controlled economically. Nearl} all the severe loss of 1907 could have been averted had the growers known the proper remedy to apply. The writer has fun ml the following insecti- cide \ci-\ efficienl in killing the beetles and nol at all injurious to I he plants: Arsenate of lead (in paste form, or \ pound powdered form i. pound.. 1 Water " gallons. . L2 to 16 Mix the arsenate of lead thoroughly in a small quantity of water, pour into the tank, and add sufficient water to make the desired ipiantit \ ; t lien apply to the bed with a spray pump until every leaf is thor- ough!} dampened. Two very good spray pumps are illustrated in figures ."> and • >. If a heavj rain falls soon after tlie application is made it may be neces- sar} to make a second application; but it must be remembered that arsenate Of lead will stick to the foliage much longer than Paris green, and will nol be greatly dissipated by a lighl shower. After tin' plants have grown consider- ably it will he tiece»arv to spraj the bed again if flea-beetles are still numer- ous, for the new foliage will, of course, not he protected by the first applica- tion. If flea-beetles are very numerous at the time of setting tobacco, the plant- can he protected for several days by dipping the tops, just before setting, in the arsenate of lead spray recommended for use upon t he plant bed. If plant- are not dipped at setting time and if the flea-beetles appear in the fields in inju- rious numbers, apply the arsenate of lead, in the strength recommended above, with a knapsack sprayer (fig. • '"■ With I hi- sprayer one man can spray from o to li acre- of young tobacco in a day at a COSl of from 25 to •'!■"> cent- an acre for arsenate of lead. Tobacco growers a- a rule pay too little attention to protecting their plant beds from insect attack. The result i- that more of the l-air spray pump. 6 METHODS OF CONTROLLING TOBACCO INSECTS. crop has to be set late than would he the case if the beds were pro- tected. The grower should always be prepared to fight the flea- beetle, for often prompt attention to insect attack upon the plant bed will enable him to save his bed and thus be prepared to set all his crop early. An early-set crop of tobacco has two very important advantages over a late-set crop. The first is the production of a better grade and of more pounds to the acre, as mentioned above. The second advantage is often more important than the first. An early-set crop will frequently mature in time to be cut before the August "shower" of tobacco worms is large enough to do it serious injury. This point will be explained more fully in the fol- lowing discussion of the tobacco horn- worms. THE TOBACCO HORNWORMS. (Phlegethontius sexta Joh. and Phlegeikontius quinquemaculata Haw.) In the "dark tobacco" districts of Kentucky and Tennessee the horn- worms are the most injurious tobacco insects, and they are important enemies of this crop in every district in the United States where it is grown. There are two species, the northern tobacco worm (Phlegethontius quinquemacuhta Haw.) and the southern tobacco worm (Phlegethontius sexta Job.) (fig. 7). The northern tobacco worm is called also the "Spanish worm" in Tennessee and Kentucky. This "worm," or larva, is in general darker than the southern tobacco worm, but the easiest way of distinguishing the two species is by the white markings on the sides of the body. The northern worm has S V-shaped markings on each side of the body, each of which incloses a spiracle, or breathing pore. The southern worm has 7 oblique lines on each side of the body, each of which passes in front of a spiracle. DISTRIBUTION. In general, as the common names indicate, the northern worm is most numerous in the north and the southern worm is most numerous in the south. The northern species is found as far south as Florida, though it is rare, and the southern species has been collected in Canada. At Washington, D. ('.. on the authority of Dr. F. II. Chittenden, the northern species predominates, while in Tennessee Fig. G. — Knapsack spray pump. Ml CHODS OF CONTROLLING COBACCO [NSE< is. / the southern species is much the most abundant. These two species are so nearly alike in their work, life liiston . and seasonal history thai the remedial measures which apply to one will apply equally well to the other. The life history and seasonal history notes given in tins article are from observations upon the southern species {Phlege- thontivs sexto Joh. LIFE HISTOm A\H SEASONAL HISTORY. This circular does not propose to describe in detail the life history and seasonal history of the tobacco worms, bul to give only such data 7.— The Southern tobacco hornworni {Phlt gelhonliv \ l)V i- Incu- [nstars, 01 i ol 1 Fourth Days. i Fifth. Total p Din/s. Days. 1 Days. 3 3 Days. Dai/s. Days. 19.5 21 18 ^gr 'W ; Larva, fourth instar. Natural The tobacco moths, as has already been stated, begin to emerge from hibernation about June 1 . or slightly earlier, and the errn /. September 1. and September 1 5, respeel iveh . Although moths of both the first and second generations are iting i jgs during late Julj and in August, we will show later thai by far the greater percentage of them has just emerged from hibernal ion. and belongs, therefore, to the firsl generation. This fad has a very important bearing upon the recommendation of fall plowing. Tobacco worms begin to enter the soil to pass the winter (i. e., hibernate aboul the middle of August, and continue doing so until Frost. Usually they penetrate the soil to a depth of from :! to 6 inches. Several observations upon "second bottom" soils of the Cumberland River have shown the average depth to be I inches; that is, to nearly the greatest depth to which the land was plowed in pre- Noti Fort! this article the date of oviposition may 1 taking place al any time from .tune I to Jul) 15, for there will nol be a second genera- tion fi ited after the latter date. 10 METHODS OF < oXTROLLIXU TOBACCO INSECTS. paring it for the tobacco crop. After the larvae, or "worms," have reached this depth they twist and turn many times, finally forming by this action oval cells, in which in a few days they transform to the hibernating form, or pupae (fig. 8). The cells protect the pupa' much better from changes in the weather conditions than if the soil were lying in close contact to them. The insects remain as pupae in the cells during the winter and, as has been stated, begin to emerge aboul the 1st of the following June as adult moths ready to deposit eggs upon tobacco. EMERGENCE OF THE SOUTHERN TOBACCO HORNWORM FROM HIBERNATION. Careful records of the emergence from hibernation of the moths of the southern tobacco worm (Phlegethontius sexta) were kept during I he seasons of 1908 and 1909 with very interesting results. In 1908 the emergence began about the last of May and continued until August 13. In 1909 the emergence began June 1 and continued until August 22, a period of 83 days. The records of 1908 were from an emergence of 58 moths. The records of 1909 were taken from an emergence of 1,667 moths, and are, therefore, of more value than the records of 1908. The most interesting part of the data is the fact that in both years a, large percentage of the moths issued after mid- summer. Table II shows the most important data obtained from the emergence records. Table II. — Record <>/' i im rgi nee of tobacco moths from hibernation. i vi iod "i emergence. Emergence during period. Period of emergence Emergence during period. L908.o Per ct hi 34. 5 65. 5 52 63.8 1909 ' l'ir a nt. J J 7 77. :s Julv 21 in July 31 . . Julv 29 to Vugusl 9 50 July 2] In i.UgUSl 1 3 Julv 29 in Vugus! ! ' 59 i ence began aboul June 1. '• Emergence began June l From Table II it will be seen that there was a large wave of emergence in 1908 in the 11 days from July 21 to July 31, inclusive, and that 52 per cent of the total emergence took place during that period. The record further shows that after July 15, 5 per cent of the total emergence took place. In 1909 the results were very similar. The large wave of emergence took place during the 1 1 days from July 2!) to August 9, inclusive, and 77..'! per cent of the emer- gence occurred after July L5. REMEDIAL MEASURES. It has been the belief that the larger percentage of the tobacco worms that appear in late July and in Augusl and September are of the second generation. This is not true, for nearly all the worms METHODS OF CONTROLLING COBACCO tNSECTS. 11 that appear before the middle of J11I3 are killed by hand worming, ami we have already shown In means of the life-historj records thai it will be two months from the emergence of the hibernating genera- tion before the "worms," or larvae, of the second generation will be large enough to injure tobacco seriously. The statement has been frequently made to the writer, and personal observation has convinced him of its t nidi, thai no difficult} is experi- enced in keeping tobacco free of worms by hand worming until the middle of July or later. Therefore, if tobacco is not injured by worms until after the middle of July, the conclusion is that until thai date very few large tobacco worms have escaped hand worming and that the second generation from those (hat have escaped will he a very small one. Byfartht greater portion oj ''/n/wim worms that appear in /uti July and in August art tht offspring of moths that havt emerged from hibernation; for the second generation of worms, the offspring from those worms thai mature after July 15 will not be of sufficienl size to injure tobacco seriously until aboul September 15. If tobacco has been set early the crop will he ready for the barn by this date and will, therefore, escape the second generation of worms. I \ II W 11 w INTER ri.ow ING. Numerous experiments in 1907, 1 '.his, and L909 have demonstrated that as a rule < > 1 1 1 \ aboul one-fourth of the tobacco worms that hiber- nate are able to survive the winter and become adult. A part of the mortality is due to parasites, bul a greater pari of it is due to the unfavorable weather. 'The hibernating period is, therefore, a verj critical period in the seasonal history of the tobacco worm, and man\ of those that do survive this period must he greatly weakened. Hence, an\ artificial disturbance ^>( natural conditions will produce an additional mortality. As has been stated, the hibernation period is passed in t he pupal si age in an oval cell (fig. 8), about 4 inches below the surface of t he soil. The most simple met hoi I of disturbing the pupae during hibernation is to disk or plow the land. Both met hods were t rice I. It was found that t he disk would reach onhj from 5 to 111 per cent, of t he cells, and that therefore little benefil could he derived from that treatment. II, experiments in plowing th< land kitted mon than half the j>uj>:i that would otherwisi havt puss,,/ Hi, winter successfully. The ground should he plowed to the same depth as ii was in preparing it for tobacco, for manj of the tobacco worms will go down to the hard soil to form the hibernating cell, that i-, to the greatest depth to which the soil has been broken. Plowing will throw the pupa' and the cells up to or near to the surface, will break the cells in nearly all Cases, and will place the pupa' in close contact with the earth, in 12 METHODS OF CONTROLLING TOBACCO INSECTS. which condition they are most susceptible to changes in temperature and to other climate-logical changes. A week or ten da} r s should elapse between the time of cutting the tobacco and the plowing of the land, in order to give all larva' that are in the soil time to change to the more helpless pupal stage. Plow- ing should be done as soon thereafter as possible, so that the pupae will be exposed as long as possible to unfavorable conditions. It is the practice in many localities of Kentucky and Tennessee to disk the land that has been in tobacco in preparation for the wheat that is usually sowed after the tobacco crop has been harvested. In some localities it is thought that disking tobacco land is a better preparation than plowing, for the reason that plowing loosens up the soil too deeply and that the wheat will freeze out more easily. Undoubtedly this may be true for some soils, that is, soils that con- tain little clay and do not, therefore, run together very compactly. There is, however, a large proportion of clayey soils in the Tennessee and Kentucky tobacco regions in which wheat should not freeze out easily. In fact, many farmers always plow their tobacco land in preparing it for wheat because they believe they obtain a better yield. Whether it is wise or not to plow tobacco land for wheat is a question that each farmer must decide for himself. But it is certain that plowing will cause the death of more than half the pupae, while disking will kill very few. Upon the looser soils it would, perhaps, be better to change the rotation and to sow some crop other than wheat after tobacco. COMBATING TOBACCO HORNWORMS UPON GROWING TOBACCO. If tobacco is planted early the hand worming, necessary to kill all worms that appear before the large emergence wave in late July (Table II), can be made incidental to other processes in the growing of tobacco, and will require very little additional time and labor. Usually, in addition to the cultivation with farm implements, tobacco will receive the following attention: Two hoeings, hilling, priming, and topping, and much of the early tobacco will besuckered. During these necessary operations it is very easy to discover and to kill the few tobacco worms that have appeared, but when the large wave of emergence appears, hand worming will be found very costly, and in some localities impossible because of the scarcity of labor. When tobacco worms are numerous it will require an outlay of at least $8 to $10 an acre to hand-pick (lie worms, and frequently the outlay will exceed $10 an acre. Us( of I'diis green. — After the appearance of the .Inly and August "shower of worms" an application of Paris green with a dust gun dig. 10) will be found to be the mosl economical means of combat. In Tennessee and Kentucky Paris green is generally applied without .Mil HODS 0] ILLING COBAI I INSECTS. 13 a carrier, but the writer prefers to mix ii with twice its weigh! of finch powdered air-slaked lime, for when the application is made without a carrier the cloud of dust from the oozzle of the dust gun is so thin thai it is impossible to determine whether the application is being made evenly. On the other hand, if the Paris green is mixed with aboul twice its weighl of lime, t he cloud of dusl from the nozzle w ill alw a\ s show whether the gun is working properl) . and a clogging of the tubes can be discerned instantly. Apply flu dust early in the morning '/7m// tlu dew is upon thi plants and when that in no h 5 ^* -^^- -sr<^ 10.— Applying Pari obaoco with a dust gun. (Original.) Use a dust gun that has a strong fan power, and apply to onlj one row at a time. Greal care should be taken to make the application even and thorough. No definite date can be given for making the Brsl application. The time will depend upon the appearance of the young tobacco worms, and it may be the last week in duly or not until aboul the middle of August. In 1908 and L909 some of the early planted tobacco at Olarksville, Tenn., did not require poisoning, and in L909 some of it required almost no worming. The first appli- 14 METHODS OF CONTROLLING TOBACCO INSECTS. cation should be made within three or four days after the eggs begin to hatch. A thorough application of from three-fourths of a pound to 1 pound to the acre should be sufficient to kill the young larva 1 . Do not wait until the worms become half grown before making the application, for in addition to being very much harder to kill than the young ones, they will do considerable damage to the leaves before the} arc killed. In dry weather a- thorough application will remain effective for a week or ten days, but if there is a rain the application should be repeated immediately. The number of applications and the dosage will be influenced by weather conditions whether wet or dry — by the numbers of young worms that appear, and by the earliness or lateness of the crop. By watching the effect of an applica- tion it can be easily determined whether it is losing its effectiveness and whether another application is necessary. The presence of a few large worms does not necessarily mean that the poison is ineffective. Some worms will escape the most careful applications, and these should he hand picked. The strength of the later applications upon tobacco that is nearly grown may be increased to 1, 1^, or even 2 pounds to the acre. ( 'aution. --Do not apply Paris green until two or three days have elapsed after suckering, for if a light rain should wash the Paris green into the fresh wounds made by breaking out the sucker, the caustic effect of the free arsenic may cause the leaves to drop off: also, do not apply a heavy dose of Paris green to tobacco when it is beginning to "grain," for the leaves are then more susceptible to "Paris green burn" than they are a few days previous to "graining." Spraying tobacco versus dusting. — In this circular we have recom- mended dusting tobacco instead of splaying for two reasons: First, the labor of spraying is very much greater than that required to apply the dust. When tobacco is nearly full grown, that is, has begun to lap in the row, it will require from 120 to 150 gallons of water to spray an acre. Therefore, to apply the spray to 1 acre a 5-gallon knapsack sprayer must be refilled from 21 to 30 times. Second, the Paris green is not kept in suspension very easily in a knapsack sprayer and the last of the spray from the tank is likely to contain more than its proportion of the Paris green and thus cause injury to the plant. Furthermore, if great care is not used in apply- ing the spiav, a part of the plant is very likely to be drenched and the I'aiis green will be collected along the midribs and in the axils of the leaves in sufficient quantity to cause serious injury. It is no! denied (hat, a more even and thorough application can be made in spray form, but with negro labor, and with most white labor, we do not believe it, will be made as satisfactorily as in the dust form. Arsenic left upon tobacco. — There is fear among growers that if arsenicals are used a sufficient amount of arsenic mav be left Ml CHODS ni i'hxi ROLL] NG I OBA< CO [NSE< I -. 15 upon the cured tobacco tt> injure the user. This fear is groundless. Prof. II. Garman," state entomologist of Kentucky, reports the results of several experiments to determine the amount of arsenic left upon treated tobacco. Talis green was used at the late of 1 | ic n i in I to 1 60 gallons of water. The experimental row thai received the greatest amount of Paris green received 8 sprayings with a total 11.— Applying Paris green to tobacco with a knapsack spray pump. (Original.) of I' pounds to the acre. The last spraying was made Augusl 22, and the tobacco was cut September I. Analysis of this tobacco showed 0.651 grain arsenious oxide to the pound. In the several experiments performed l>\ Professor Garman only one experiment gave mimic than one grain of arsenious oxide to the pound of dried tobacco, and the tobacco in this experiment was sprayed the daj it Bui 63, K> \ i I up. Sta . pp 69 16 METHODS OF CONTROLLING TOBACCO INSECTS. was cut. Professor Garman concludes that very little danger may be apprehended from the arsenic left upon tobacco. In 1909 the writer made several experiments to determine the amount of arsenic left upon tobacco. To make the test severe, arsenate of lead was used because this arsenical adheres to tobacco much longer than does Paris green. August 13 the experimental plat received a spray- ing at the rate of 5 pounds to the acre, and on August 18 a second spraying at the rate of 4 pounds to the acre. Arsenate of lead in dust form was used, hence the two dosages, amounting to 9 pounds, were almost exactly equivalent in the amount of combined arsenic to Professor Garman's dosage of 4J pounds of Paris green. The tobacco was cut September 8. The analysis, made by the Miscel- laneous Division of the Bureau of Chemistry, showed an average of 0.347 grain arsenious oxide per pound. Heavier dosages of powdered arsenate of load left only 0.501 and 0.531 grain arsenious oxide per pound. A fatal dose of arsenic for an adult is about two-thirds of a grain, and this, of course, has to be taken into the stomach. Since tobacco is not taken into the stomach, and since so little arsenic will be taken into the mouth at anyone time, it is not believed that there is the slightest danger in using tobacco that has been poisoned with either Paris green or arsenate of lead; in fact, the writer is per- sonally acquainted with tobacco growers who have been applying Paris green to their tobacco for from six to eight years and who have been chewing and smoking the cured tobacco without injurious effects. POISONING THE TOBACCO MOTHS. The custom of poisoning " jimson" blooms with arsenide of cobalt (flystone) to kill the tobacco moths when they feed has long been recommended and has been practiced in nearly every tobacco region, but unfortunately the custom has fallen into disuse. This method of combating tobacco moths should be revived, for the kill- ing of one female moth at " jimson" blooms will be equivalent to the killing of several hundred worms later. The following is the formula for this poison: Arsenide of cobalt I flystone) ounce. . 1 Water pint. 1 Sweeten, just before using, with molasses or honey. Place a few drops in each bloom late in the afternoon. SUMMARY. CUTWORMS. 1. Plow sod land in the fall in preparing it for tobacco and keep down all vegetation during the winter and spring. This will starve the cutworms. MKI HODS OF CONTROLLING COBACCO tNSE( CS. 17 2. [f sod land has no! been treated as recommended above, use the poisoned bail four or five days before setting tobacco, or drop the bait aboul each lull directrj after setting tobacco. FLEA-BEETLES. 3. Canvas seed beds tightly with strong whole canvas and thus prc\ cni cm l \ of i he beel les. I. Spiay infested l>e arsenate of lead recommended in No. 4. (i. [f flea-beetles continue to injure plants after setting, spray with arsenate of lead at the strength given above. n Hi \( ( < > lloKN W OHMS. 7. Nearly all the destructive late July and Augusl "shower" of worms is the direct offspring of tobacco ninths thai have issued from hibernation during late July and early Augusl . 8. Over 60 per cent of the hibernating generation of ninths emerge from hibernation late in July and in August. 9. Fall plowing of land that was in tobacco during the year will destroy more than half of the hibernating generation ami will thereby reduce proportionately the Dumber of tobacco worms that will appear the next year late in July ami in August. in. Poison worms upon tobacco plants by dusting with Paris green. 11. Poison tobacco moths In placing a few drops of arsenide of cobalt (flystone solution in "jimson" blooms. Approved : .1 \mi> Wilson, .s, cretary of Agricultun . Washington, D. ('.. April is. 1910. UNIVERSITY OF FLORIDA 3 1262 09216 5249