JUNE 1966 TEXA S B UL LNE TTLE and its Control TEXAS A&M UNIVERSITY Texas Agricultural Experiment Station R. E. Patterson, Direct‘or, College Station, Texas C ON TEN TS S UMMAR Y Cattle Will avoid areas heavily infested with Texas bull- nettle when forage is available elsewhere. Estimates of for- age utilization losses range from 14 to 100 percent from bullnettle-infested areas. Control of this perennial weed de- ‘it pends upon destruction of buds located at depths of 3 to 22 inches or more along the stem and on the crown of the tuber (primary root) ; destruction of the aerial portion causes only a temporary setback of the plant. Quick topkills achieved by strong solutions or oil-based herbicides evidently destroy the cells by which the herbicide is translocated to the roots. Thus, translocation is reduced or stopped, allowing regrowth to occur. A solution of 0.1 per- cent 2,4-D amine in water Summary ---------------------------------------------------------------------------------------- " 2 or (ggmblned per- IIItTOdIICtiOTI --------------------------------------------------------------------------------------- -- 3 cent picloram and 0.25 Bullnettle Root ................................................................................. .. 3 percent surfactant killed Aerial plant ______________________________________________________________________________________ __ 5 85 to 95 percent of the Propagation ___________________________________________________________________________ __- __________ __ 6 complete plants with one . - spraying when applied Parasites ............................................................................................ -. 7 before fun bloonL A 0.1 Grass Production and Near Bunnettle ------------------ -- 8 percent Sglutign is a- Materials and MelihOdS f0? COI1tT01 ----------------------------------------------- -- 8 chieved with 1 ounce 0f Results and Discussion .................................................................. -- 8 a 4 pounds per gallon Acknowledgments _____________________________________________ _____________________________ __11 solution of 2,4-D in 3 gal- Literature Cited _______________________________________________________________________________ "11 lons of water; a 0.25 Appendix ____________________________________________________________________________________________ "11 percent solution results from 2 tablepsoons of surfactant in 3 gallons of water (a 0.1 percent solution by weight is approximately equal to a 0.25 percent solution by volume). Amitrole induces bud dormancy, as do some other herbi- cides to lesser extent, but the plant may become active again after 1 to 3 or 4 years. If plants cannot be treated with 2,4-D, they can be destroyed by cutting off the crown of the tuber. All aerial growth buds are located on the crown and on the stem between the tuberous root and the surface. No adventitious growth buds are formed below the crown, but a damaged root system may be replaced by adventitious roots. BULLNETTLE, Cnidoscolus team-nus (Muell. Arg.) Small is a vicious, stinging plant of the family Euphorbiaceae, having an annual herbaceous top and a large, fleshy underground perennial tuber, 0r root. It is found in all vegetational areas 0f Texas except the High Plains (2). Within those areas it is found on the sandy and sandy loam soils, rarely on the clays. Some authors (1., 5) say the range of closely related C. stimulosus (Michx.) Gray extends into Texas, but Marshall C. Johnston, University of Texas Herbarium; Rogers McVaugh, University of Michigan Herbarium; and Grady L. Webster, Department of Biological Sciences, Purdue University (per- sonal communications) all agree that these Texas plants are .1; C. texavzus. The accepted l common name is Texas ~ P R JOHNSON, bullnettle; other names '1 ' ' are tread softly, Texas tread softly and mala mujer. The horsenettle (Solamun caro- Zinense L.), an entirely different plant, is sometime called ball- nettle, or bullnettle and is confused with the true bullnettle. Several authors (1, 5, 7) have described the aerial por- tions of the plant ‘but only describe the roots to the extent that they are perennial, long, thick, stout, tuberous, tough or woody. Stewart, Reeves and Jones (8) have given a good description of the complete plant, together with photographs. They reported a root 7.75 inches in diameter and 4 feet long weighing 44 pounds. They also reported small knoblike, fluid- filled glands on the tips of the numerous spines that cover the leaves ‘and branches of the plant. When a person or animal comes in contact with the spines, these glands break off and remain enbedded, and cause an unpleasant sting. Stewart, et al. (8) reported some field control of bull- nettle by placing a solution of white arsenic and lye into the root, but only topkill resulted from spraying the plant with Atlacide. Young (9) reported good topkill with a drenching spray of 0.1 percent solutionl of 2,4-D LVE, but many plants renewed growth the next year. Johnson (3) found that bull- nettles can be controlled with 2,4-D amitrole and 2,3,6-TBA and that the chemicals may induce dormancy for 1 or more years. Klingman (4) emphasized the effective translocation of herbicides to perennial roots when large amounts of food reserves were being moved downward. He also pointed out the fallacy of excessive rates and quick topkills. r Bullnettle Root In the course of investigations on the control of this weed, several roots were excavated. The underground portion of the plant may be divided into three main parts: the stem, the tuber or primary root, and branch and feeder roots, all of which are perennial, Figures 1, 2, 3 and 6. The large, fleshy, tuberous root is the most conspicuous. Data on several excavated tubers and stems are shown in Table 1. Branch roots usually arise ‘=1. *Superintendent, East Texas Research Station, Tyler ‘Solution percentages are by weight—not by volume. Figure 1. From leftr Seedlings, 1-year-old root, other roots of unknown ages. Largest tuber shows remnants of four stems. Legend.‘ A —stem, B-collar, C— bud zone (includes stem and collar), D— tuber. near the base 0f the tuber, Figure 1, but may be found nearer the crown. In outward appear- ance and in cross section, branch roots are similar to the main tuber. The small feeder roots are light brown in color, threadlike and are brittle. Usually, only short sections of feeder roots can be removed without breaking. The “usual” tuberous root is somewhat carrot shaped, being round, tapering from top to bottom and with few branch roots except at or near the bottom, Figures 2 and 3. The shape is largely determined by soil conditions. Deep, loose sand is conductive to long, smooth tubers, while shal- lower sandy loam with clay subsoil is conductive to short, thick, stubby tubers. Large rocks in the soil may cause the tubers to be short or to have more branches, Figure 2. In cross section the tuber shows rings similar to annual growth rings of trees, Figure 4.x Ste- wart, et al. (8) suggested that these were growth rings, but attempts to correlate the rings with age failed. Young roots of known or closely estimated age might show more than one ring per year, while inability to determine age of older roots precluded their use. It may be that these concentric rings are storage parenchyma and have no correlation with age. Similar rings were found by Myers, Beasley and Derscheid (6) in roots of Euphorbia esula L. The crowns of the tubers were found from 3 to 22 inches below the soil surface. Stewart, et 4 the crown and stem suggested that the pl al. (8) reported a crown 27 inches below i surface and concluded that as the root i older it contracted and the crown sank. , assumption must be true for the first year the plant’s life, as the crown is formed near surface initially. Other undetermined fac also influenced the depth of the crown. In} series of 69 roots excavated from pasture in s, the soil had not been disturbed for approxima. 30 years, there was a range of 3 to 18 in in the depth of the crowns. Diameter of , root was taken to be indicative of the rela age of the plant. The root diameter was significantly and negetatively correlated depth of the crown, r I --.()411. One or more stems may develop from crown. The buds from which the annual a, growth develops arise from the stem or buds on the crown. Usually only one to t or four buds will produce aerial growth season, and these will ‘be the buds nearest l. soil surface. When part of the stem or . crown and stem is exposed, the aerial will develop from the lower buds and the exp stem will die. No aerial growth buds have been f0 lower than the crown. Attempts to induce ini tion of buds at lower levels by removing the cr. have not been successful. This has been t, for roots left in place as well as for those trj - planted to the greenhouse. l “The localization of aerial growth buds could be controlled by mechanically cutting a the crown and leaving the rest of the root; place. No aerial buds developed on manu decapitated roots after 3 years or on roots ' chemically destroyed growth buds after 4 a Figure 5. Where decapitation was incompl new stems developed from remaining buds, Fi A 3. Figure 2. Variation in tuber shapes. Tuber on right i countered rock at the point of the upper branch root. 3. Normal shape and location of branch roots. Gopher had destroyed part of crown; there is spade injury ' crown. iltoot growth from adventitious buds was instrated in the greenhouse and in the field, res 6, 7 and 8. ffwo roots cut off l}; inch and two cut off iteinches below the crown on July 25, 1962, to develop adventitious roots on the crown ii-‘on. They did make some aerial growth g 1962 but not in 196s or 1964. When ined on August 24, 1964, they were de- t o... with no evidence of root formation. Two - ii; cut off 3 inches below the crown and potted e greenhouse formed adventitious roots and inued aerial growth, Figures 6 and 7. This id suggest that if control by cutting off the is practiced the crown should be left un- Cred and allowed to dry out. Deep plowing g a moldboard plow would cut some pre- jisly undisturbed roots below the crown, and crowns might form new plants. However, plants so propagated have been identified in i. field. TABLE 1. SOME CHARACTERISTICS OF BULLNETTLE TUBERS Number tubers jacteristic examined Average Range i is of crown surface 105 8.8 inches 3 - 22 inches . length 83 2.7 inches 0.75 - 10.0 inches eter of tuber T lap 139 " 2.9 inches 1.0-5.8 inches 1 eter of tuber i bottom 95 1.8 inches 0.5-4.5 inches _th of tuber 117 18.6 inches 9 - 52 inches of tuber 94 3.8 pounds 0.1 - 20.7 pounds me of tuber 93 105.4 cu. in. 5.8-566.4 cu. in. ber of buds crown 31 5.1 0 - 18 Buds on the crown and stem, except for one to four of the uppermost, remain dormant unless exposed to light. This characteristic was used to distinguish between dormant buds and those dead from herbicide or other causes during January and February of 1965. Two lots of 19 and 77 tubers were stacked in horizontal layers with crowns exposed on a soil bed in the greenhouse. They were covered with clear polyethylene and kept moist. Minimum night temperature was 60 degrees F. and maxi- mum day temperature with bright sun was 85 to 90 degrees. All viable buds commenced growth with- in 15 to 20 days. Number of viable buds on the crowns ranged from none to 18. Viable and dead buds also may be distin- guished macroscopically by cutting away the bark and the bud scales and examining the meriste- matic tissues. This method is tedious and poss- ibly less accurate than by forcing growth. Aerial Plant The annual aerial plant emerges from the perennial root and stem system at approximately the average date of last killing spring frost. Figure 4. Cross sect-ion of tubers. Figure 5. Herbicide damage to stems, crowns and side 0f tubers. Plants were sprayed in 1960 and tubers were removed from soil in 1.964. N0 aerial growth occurred following spraying. Emergence usually is complete 60 to 75 days later. Plants cut off near the surface will resprout up to August or later. One t0 four stems may emerge from a single root system, and occasion- ally two or three roots may be growing in such close proximity that several stems appear to arise from the same root. Early growth is upright; older plants are much branched and semi-erect with a horizontal spread up to 54 inches and height up to 30 or 36 inches. Size of the plant is not indicative of root size after the first few years. Growth of undisturbed plants usually is complete by late August or September, and they often die down before frost in early fall. Leaves are large, deeply lobed (3-5, mostly 5-lobed), roundish-cordate, alternate and on long petioles. Late season leaves sometimes are dis- colored yellowish or chlorotic. The flowers are monoecious, white, fragant, about 1 inch across and on a terminal cyme. The pistillatelflower is on a short stalk and has a three-celled ovary sur- rounded and over-topped by staminate flowers on longer stalks. There are from one to four of these pistillate-staminate groups in each flower cluster. Stems, branches, petioles, leaves and seed capsules are covered with white, stiff, stinging hairs or spines. On the leaf the spines are prac- tically all on the midrib and veins, with some be- tween the veins. They are on both the upper and lower leaf surfaces. Figure 6. Adventitious roots on upper 3-inch sect Y tubers. . Propagation Bullnettles are propagated by seed. are large, bluntly oval, 11/16 inch long by . to 7/16 inch wide and average 0.32 grams each, or about 1,400 per pound. They are ;i in a three-locule capsule which dehisces o turity with considerable force. A seed f I capsule on an office desk struck a filing f 6 feet away, and another from the same cal was thrown behind an open door 54 inches than the desk and 8 feet from the point of o Seedlings have been found 15 feet from any producing plant. Figure 7. Location of adventitious roots. Same tubers as in figure 6. Squirrels and possibly other wild animals the crown completely destroyed. Enough buds _ d birds eat the seed and may disseminate them. were left to reestablish the plant. The stems and cultivated fields young seedlings have emerged tops apparently are completely eaten. Tops were y.» depths of 1 to 4 inches. observed being pulled into the ground as is typical of this rodent when eating aerial plants. Roots ' were uncovered with gopher runs contacting the Parasltes root below the crown, then turning up to and over The only parasite found to attack the roots s the crown. Gopher tooth marks on partially de- the pocket gopher. The crown, stem and aerial capitated roots further identified the parasite. rts are eaten; no tuber has been found with It has not been possible to determine the amount of damage done to bullnettle by gophers. The gopher population level would be an important consideration. These investigations were con- ducted with a light infestation. Damage done to underground parts can be assessed only by gure 8. Root decay from bottom upward. Plant at left Fl; sprayed June 13, 1961 and removed July 25, 1962. ‘cay probably would have involved the entire root if left isturbed. Plants at right were sprayed June 13, 1961 removed Dec. 16, 1964. Adventitious roots were ‘ ed, viable buds were present and small aerial growth Figure 9. Animal did not graze within spread of bull- lrred in 1961,, but not earlier. nettle plant. 7 TABLE 2. EFFECT OF BULLNETTLE ON PRODUCTION AND UTILIZATION OF COMMON BERMUDAGRASS Yield, pounds per acre‘ Percentage of caged bermudagrass " 5/31/61 4/1/62 5/28/62 8/6/62 5/31/61 4/1/62 5/28/62 I to to to to to to to _ Source of sample 8/23/61 5/28/62 8/6/62 10/22/62 8/23/61 5/28/62 8/6/62 10 Grass, protected by cages 5880 2701 3615 2252 100 100 100 Grass, in open, grazed 1568 1655 610 305 26.7 61.3‘. 16.9 Grass, protected by bullnettle 4530 3006 1437 2178 77.0 111.2 '1: 39.7 Grass, protected by bullnettle and cage 2788 2091 77.1 Bullnettle, in open , 871 1002 1699 871 Bullnettle, protected by cage 566 52 ‘Yields in the designated areas; effect on larger areas would depend on stand of bullnettle. uncovering and examining the growth buds 0n the stem and crown; that to the aerial portion can be assessed only if part of the damaged plant is found. Some evidence has indicated 4 percent of the tops killed. Few insects were observed attacking bull- nettle. A long-horned beetle larve (Ataxia sp.) was found in a dead aerial stem. Fall armyworms and grasshoppers were observed eating forage, but only when other vegetation was limited. Grass Production and Utilization Near Bullnettle Cattle will avoid an area heavily infested with bullnettle when adequate forage is available elsewhere. Even when animals do graze among the plants, the grass growing near and within the spread of the plant is left, Figure 9. When graz- ing pressure is heavy, grass leaves developing above the nettle may be utilized. In order to esti- mate the grazing loss caused by bullnettle, yields were estimated using a series of cages in quad- ruplicate in an infested pasture. The yields are shown in Table 2. It is difficult to determine the effect of the nettle on grass production. Data in- dicate that during spring and fall as much grass is produced within the spread of the nettle as in the open. Grass production appears to be reduced 20 to 60 percent during the summer. A moderate stand of bullnettle may ‘be 650- 750 per acre. Since an average plant will cover an area of 12.5 square feet, 700 plants would cover 8,750 square feet or approximately one-fifth acre. Thus, a major loss in utilization would occur even if grass growth was not significantly depressed. Materials and Methods for Control Natural stands of bullnettle were used throughout the study. The plants were of vary- ing ages, and no satisfactory way of determining ages after the first few years is known. After the first 3 years the younger plants were not included in the test. Initially, the work was conducted on a plot basis, but this was not fully satisfactory in that are given in the Appendix. ' plant locations could not be maintained for q roots that did not produce new top growt year following treatment. Some roots were sidered killed when in fact they were i," dormant. A system of individual plant iden tion was then adopted whereby embossed indicating treatment number, year and plant , ber were nailed to stakes beside each plant. » Plants were individually sprayed at 3 40 psi to the point of spray run-off. A surfa was used only in 1964. The amount of sol used per plant varied with size and averaged‘ fourth pint. Chemicals evaluated in these st i are listed in the tables. Common names acc by the Weed Society of America are used 5 the herbicides included. The full chemical :._ Plants in the numbered series were class’ as dead or dormant after excavating the p site and finding evidence of a decayed root examining the crown and stem buds. Dou buds were checked by macroscopic examina or by forcing growth. Part of the 1964 numb series were- uncovered and the crowns left exp in place, during spring and summer of '~ Some of the amitrole-treated plants may have L too dormant to respond to light stimulation. 1 Results and Discussion Plants were mowed once, twice or three ti each year for many years with no apparent eff on population. Plant reestablished rapidly w‘ cut off above the soil surface. ‘ a Some chemical treatments have the sat effect as mowing in that a quick top kill prev translocation to the roots and the buds on v stem and tuber crown. It was shown by Kli man (4) in his review of the literature on t - = ~ location of herbicides that extremely toxic ch icals or excessive rates will stop translocati _ to the roots with much the same effect as cutti off the top. Results of the 1957 spray treatments =é shown in Table 3. Plots in triplicate were spray August 13, 1957. One replication had been mow on June 5; the regrowth was maturing. v other two replications were mowed on July k and the regrowth was in bloom when trea =7 7 3. THE EFFECT OF CHEMICAL TREATMENTS ON BULLNETTLE, KCIITHBERT GRAVELLY SANDY LOAM SOIL Treatment Pounds OT 1 chemical Apparent per 100 sprayed surviving survival Carrier gallons 8/13/57 6/19/58 (percent) diesel oil 4 pounds 128 128 100 diesel oil 8 pounds 159 149 94 water 4 pounds 133 140 105 diesel oil 4 pounds 135 147 109 diesel oil 8 pounds 154 150 97 water 4 pounds 130 140 108 water-oil-Fab 4-95-5-1 170 87 51 water-oil-Fab 8-95-5-1 158 73 46 water 4 pounds 155 148 95 water 6 pounds 154 176 114 1 14 1 38 1 21 1 included seedlings. f: counts were made 0n August 12, before ying, and 10 months later on June 19, 1958. ‘=1 counts included some seedlings, so the possi- - remains that unsprayed seedlings were ted in 1958 that were not included in the count. The near 100 percent survival on iexcept the amitrole plots shows the ineffec- i ess of the treatments. Stage of growth when "yed had no effect on the results. Later re- = indicate that much of the apparent kill with role was simply induced dormancy. Applica- is of 2,3,6-TBA in 1960 showed that the 1957 1:»; of this material were too low for effective rol. Other observations have shown that gaso- kerosene and naptha along with diesel oil unsatisfactory carriers of herbicides for bull- because of the quick topkill by these " rials. ,- The 1959 and 1960 treatments and results are ’ in Table 4. The plants were sprayed in full bloom stage June 29, 1959 and early Q1 stage June 3, 1960 using the same plots. tments were also the same each year except liquid amitrole was used in 1960 instead ,2,3,5,6-TBA, and 0.1 percent 2,4-D amine used instead of 0.5 percent 2,4-D LVE. Plant counts on June 29, 1959 included an unrecorded number of seedlings. Mortality among the seedl- ings was high, making the apparent control look better than it really was. Later counts separated seedlings and young plants from older plants, and survival percentages are based on old plants. There also was a small undetermined amount and distribution of seasonal loss due to gophers. Amitrole continued to show good control for the season of application and the year follow- ing. During the third year after application several plants emerged from roots that were dormant for 2 years. The characteristic of dor- mancy, rather than control, following the appli- cation of amitrole and some other materials also was found in later investigations. The 2,3,5,6- TBA was not satisfactory for bullnettle control. Later comparison of another benzoic acid on two soil types showed better control on the more sandy soils. Soil on parts of the 1959-60 plots was comparatively shallow. The rate of application was later found to be too low. 2,4-D generally gave satisfactory control, except that high rates gave quick kill and apparently did not allow suf- ficient translocation to the root. The amine formulation apparently was better than the ester. Control based on semi-permenently identified plant locations is illustrated in Tables 5 and 6. The treatments were applied to 50 plants each in 1960 and 1961. Records of regrowth were made twice yearly until the fall of 1964. Each plant site was excavated and the condition of the tuber noted. Tubers in various stages of decay were recovered, and open holes from which the root had decayed were found. Decay often started at the bottom of the primary root and progressed upward. In "some instances decay apparently was arrested and the plant was recovering, Figure 8. In other instances the bud zone at the collar and on the stem was destroyed, in which case no further aerial growth was made, Figure 5. Vari- ous other degrees and locations of partial decay also were found. Viability of the buds was deter- mined on roots which were recovered. Plants were classified as dead when the buds were dead, the bud zone was destroyed or when the root TABLE 4. THE EFFECT OF CHEMICAL TREATMENTS ON BULLNETTLE PLANTS 1959-60 1960-1962 Apparent percent A Number of Number of Apparent Number of Number of h sgyzlléjgz .. plants plants percent plants plants f 7- -. and sprayed found survival sprayed found ’ lation 6/29/59‘ 6/1/60 6/1/60 6/3/60 5/28/62 6/29/59 to 6/3/60 - 1v: .1 percent 261 so 19 so 4o 1s so ‘l1 LVE .25 percent 187 53 28 53 25 13 47 l" LVE .50 percent 178 81 46 <~ ,6-1'BA 4/ I O0 3i. I ‘I72 77 45 ,6-TBA 8/100 '~ 210 126 6O 7 le 4/100 223 17 8 17 65 29 382 ; Io 8/100 182 21 12 21 29 16 138 ' —not treated 243 15a 6s 15s 1s4 6a 97 I Amine .1 percent 81 35 20 43 ' Ale, liquid, 4/100 77 34 20 44 3 le, liquid, 6/100 126 16 8 13 n1 on 6/29/59 included seedlings, most of which failed to survive. Count on other dates are of old plants only. TABLE 5. CONTROL OF BULLNETTLE PLANTS 4.5 YEARS AFTER SPRAYING SECOND-GROWTH PLANTS JULY 12, 1960, BOWIE AND ‘_ FINE SANDY LOAM SOILS Percentage of roots and open root holes locatedl Dormant Crown not decayed f9" l 9" 2 Number of Stem, and ii years, Live plants Material and plant Roots crown ‘Buds Buds growing not Total formulation locations decayed decayed dead viable in 1964 ,__ dormant dead‘, 2,4-D Amine, 0.1 percent 44 64 7 9 4 16 Amitrole, powdered, 4/100 41 44 12 7 24 12 Check’ , 48 100 2,3,6-TBA, 1 gm./plant 42 4O 5 2 7 45 2,3,6-TBA, 2 gm./plant 4a 77 2 4 2 1s 2,3,6-TBA, 3 gm./plant 48 9O 2 8 2,3,6-TBA, 4 gm./plant 5O 90 2 8 ‘October 15 and December 16, 1964. ‘As of 7/24/62, area taken by highway. had decayed completely. Where viable buds were found, even though no growth had been made for 3 or 4 years, the plant Was classified as dormant and potentially able t0 reestablish itself. The treatment of 0.1 percent 2,4-D amine resulted in 8O percent and 7 0 percent control for the 1960 and 1961 sprayings, respectively, and Was better than the LVE formulations. This control was exceeded by 2,3,6-TBA at 3 and 4 grams per plant during 1960, but 2,3,6-TBA was not satisfactory in 1961 on shallower, less sandy soils. The 2,3,6-TBA and other benzoic acid formulations acted partially through leaf absorption and partially through root absorption. On the shallower soils the feeder roots were largely in clay which the herbicide penetrated sparingly or not at all. The amitrole products induced bud dormancy more than any other material. Counts of plants emerged 12 or 24 months after spraying indicated outstanding control, but some plants emerged during the third year after spraying, and even longer dormancy and emergence is possible. Aerial parts that emerged from dormant buds of amitrole-sprayed plants showed distinctive discoloration caused by this material during the early stages of growth, but changed to normal green 2 to 4 Weeks after TABLE 6. CONTROL OF BULLNETTLE PLANTS 3.5 YEARS AFTER SPRAYING JUNE 13, 1961, CUTHBERT AND KIRVIN GRAVELLY SANDY p‘ emergence. Emergence from dormant bu curs at any time during summer. ' Another series of staked plants were sp i on June 22, 1964, in order to test picloram Y don) and dicamba (Banvel D), in compa with previously tested materials. The plants ‘ in one-half to full bloom. Many sites were; but those that could be l-ocated were exca January 29, 1965. Roots were left in plac. with the crown uncovered throughout 1965. trol evaluated solely on completely decayed J_. was very good for 0.25 percent 2,4-D LVE 0.1 percent 2,4-D amine. The other mate and combinations produced less favorable re Table 7. The amitrole treatment resulted i percent of the roots being classified as ha dead buds, but previous experience with this. terial raises doubt as to the» accuracy of _ classification. Very good apparent control 4 on decayed roots plus apparently dead buds? obtained with picloram, picloram-2,4-D co 4 ations and dicamba. a Results of spraying unstaked plants 0n‘ finitely outlined areas during 1964 are s , in Table 8. Picloram and picloram-2,4-D t. gave very good results based on counts mad SOIL Percentage of roots and open root holes locatedl Dormant Crown not decayed f“ l °" 2 Number of Stem, and a years, Live plants - Material and plant Roots crown Buds Buds growing not Total - formulation locations decayed decayed dead viable in 1964 dormant dead 2,4-D LVE, 0.1 percent 50 24 76 2, 2,4-o LVE, 0.25 percent 43 5s 2 s9 2,4-D Amine, 0.1 percent 47 64 6 6 23 7 Amitrole, liq., 4/1OO 46 5O 17 26 2 4 6 Amitrole, liq., 6/100 48 5O 2 10 25 6 6 6 Amitrole, powd., 4/100 42 5O 2 7 31 7 2 Amitrole, powd., 6/100 43 33 19 28 19 2 5 Check 49 2 98 g 2,3,6-TBA, 2 gm./plant 36 19 3 22 55 2 2,3,6-TBA, 3 gm./plant 47 23 2 6 2 6 6O 3 2,3,6-TBA, 4 gm./plant 45 29 4 2 7 58 3 ‘December 16, 1964 1U i: CONTROL BASED ON ROOT EXAMINATION: SPRAYED “P0550 1/29/65 Acknowledgments 3* The following firms furnished the herbicides used in this study: Amchem Products Company, Dow Chemical Roots located and plant decayed dead alive percent locations percent percent percent control ' m 2o 9o s 5 9s ' I C ent 28 86 11 3 97 i, gal. 41 i 9s s 9s 0.1 g 16 31' s6 13 a7 0.1 percent a m 23 61 3s 4 96 ,4 K] gal. 23 35 s2 13 a7 ' tX-77 surfactant added to each formulation. later. When older plants were sprayed .2 percent picloram the control Was less ,: t obtained with young plants and weaker ~ s. e control obtained with a surfactant was as better than that obtained previously with- ? so the effectiveness of the material was a inished and possibly was enhanced. me essentials to satisfactory control were ‘ ntly apparent in these studies. Young, 21g’ plants were easier to kill than older ones. 1 that have passed the full bloom state should wed and the regrowth sprayed. A weak n of a hormone-type herbicide using a 1 carrier is preferable to stronger solutions hose resulting in a rapid topkill. Soil he is related to effective control by 2,3,6- plants on sandy soil are killed more readily. "s. CONTROL BASED ON neonowm or PLANTS m AREA g owmo YEAR Number Number of f of plants Apparent y ‘ql Date plants found percent tions‘ sprayed sprayed 6/30/65 control , 0.1 percent, A, 0.1 percent 6/23/64 93 112 88 ' , 0.1 percent, 'A, 0.1 percent 8/24/64 48 5 9O J , 0.1 percent 8/24/64 33 5 85 A‘, 0.2 percent 8/25/64 s1“ 23 ss Epercent X-77 surfactant added to each formulation. i 65. _. old and inactive plants. Number uncgvered Company, E. I. DuPont de Nemours and ‘Company and of Roms buds Apparent Velsicol Chemical Corporation. Literature Cited 1. Fernald, M. L. 1950. Gray’s Manual of Botany, 8th ed. The American Book Company. 1632 pp. 2. Gould, F. W. 1962. Texas Plants—A Check List and Ecological Summary. Tex. Agr. Exp. Sta. MP 585. 3. Johnson, P. R. 1963. Chemical Control of the Bull- nettle. Proceedings, S.W.C. 16:99-104. 4. Klingman, G. C. 1961. Weed ControlzlAs a Science. John Wiley and Sons, Inc. 421 pp. 5. Muenscher, W. C. 1955. Weeds. 2nd ed. The Mac- Millan Co. 297 pp. 6. Myers, Gerald A., Charles A. Beasley, and Lyle A. Derscheid. 1964. Anatomical Studies of Euphorbia esula L. Weeds 12:291-295. 7. Schulz, Ellen D. 1928. Texas Wild Flowers. Laid- low Bros. 505 pp. 8. Stewart, Ralph T., R. G. Reeves, and L. G. Jones. 1936. The Spurge nettle, J. Amer. Soc. Agron. 28:907- 913. 9. Young, P. A. 1951. Chemical Control of Weeds in Converting Pasture Land to Tomato Production in ‘East Texas. Tex. Agr. Exp. Sta. Prog. Rpt. 1338 —3 pp. APPENDIX Common and Chemical Names of Herbicides Used Common name Brand namesi Chemical name Amitrole (Various) 3-amino-1,2,4-triazole. Dicamba Banvel-D 2-methoxy-3,6-dichlorobenzoic acid. Erbon Baron 2-(2,4,5-trichlorophenoxy) ethyl- 2,2-dichloropropionate. Picloram Tordon 4-amino-3,5,6-trichloropicolinic acid. Silvex Kuron 2-(2,4,5-trichlorophenoxy) propionic acid. 2,4-D amine (various) Alkanolamine salts (of the etha- nol and isopropanol series) of 2,4-dichlorophenoxyacetic acid. 2,4-D LVE (various) 2,4-dichlorophenoxyacetic acid, propylene glycol butyl ether ester. 2,3,6-TBA Trysben 200 2,3,6-trichlorobenzoic acid. 2,3,5,6-TBA Benzac 354 Dimethylamine salt of tetrachloro- benzoic acid—20 percent, Dimethylamine salt of trichloro- benzoic acid—-15.2 percent, Dimethylamine salt of other poly- chlorobenzoic acid—12.5 per- cent. lBrand names are given for information only. ll Texas AGM University Texas Agricultural Experiment Station College Station, Texas 77843 fifizw Director Publication-Annual Report or Bulletin or Report oi Progress Permit 1105 OFFICIAL BUSINESS h,» ‘y. Penalty for priv payment of - i