PACTORS AFFECTENG THE QIFFERENNAL TOLERANCE OF TREE SFECIES TO HERBICEDES, PRIMARILY SiMAZiNE Thasis flat the Degree 64" ML D. MICHIGAN STATE UNIVERSHTY Fred Wesley Freeman 1963 / , _;_4... -._...__._..._..- This is to certify that the thesis entitled CTORS AFFECT FA ING THE DIFFERENTIAL TOLERANCE OF TREE SPECIES TO HERBICIDES, PRIMARILY SIMAZINE presented by Fred Wesley Freeman has been accepted towards fulfillment of the requirements for Ph . D. degree in Forestry Major professor Date February 19 1963 \g O~l69 LIBRARY 'l. l a .h. Uaimty r‘ ABSTRACT FACTORS AFFLCTING THh DIFFEKLXTIAL TOLERANCh OF TREE SPECIES TO HERBICIDES. PRIMARILY SIMAZINE by Fred Wesley Freeman Need control in nursery management is the most labori— ous and expensive part of the total operation. Although chemical weed control has been practiced to Some extent in the past. field evaluation and basic research are not keeping pace with the large number of new weed control agents being placed on the market. The rapidly developing chemical weed Control era in agricultural crops can also be adapted. with proper research and field appraisal. to controlling weeds in woody nursery stock. The first phase of this nursery weed research. carried on in the Bogue Forest Nursery at East Lansing. Michigan. com- pared Some of the newer soil fumigants and organic herbicides with those used in the past. Duration and thoroughness of weed control and extent of injury to germinating Coniferous seedlings were recorded and analyzed during the growing sea— son. Of the eleven different herbicides and soil fumigants tested. alone and in combination. simazine gave the best weed control over the longest period of time. Injury to the seven Species of conifers used as test plants was severe with l-chloro-J.n-bis(ethylamino)—s—triazine (simazine) treatments. White pine showed the greatest tolerance. 4.0— dinitro—o—sec—butyiphenOl. amine salt (DNBP) gave good weed control during the early growing season and caused a minimum Fred Wesley Freeman 1 amount 0f damage t” YUUng seedlings. The results obtained with DNBP indicate that additional testing of this herbicide is warranted. Further investigation of simazine rates and placement was made in greenhouse experiments with both conifers and hardwoods. White pine again proved to be more resistant to simazine than all other conifers tested. While all conifers except white pine were killed within five weeks after germi— nation by both the 4 and 8 pound treatments. red. white. and bur oak were not damaged by any of.the treatments. Surface applications were far less damaging to honeylocust and white pine than treatments in which simazine was mixed with the upper inch of Soil. Theorizing that the Species most resistant to simazine. such as white pine and the oaks. extended their roots below the zone of high herbicide concentration more rapidly than the easily killed Species. root elongation studies were made to check this point. it was found that the roots of white pine did not elongate any faster than those of simazine— susceptible Scotch and red pine. However. the roots of bur Oak moved 0 inches deep in only 13 days. With the oaks. the maximum absorbing area of the root apparently moves quickly below the zone of high simazine concentration. Addi— tinnal studies compared simazine toxicity SymPtUmS “f “3k seedlings whose root Systems were confined to the upper 3 inches of soil with those of normal growing plants. RGSUItS substantiate the belief that a good part of the t019rance in oaks is due to the root growth habit of the plant rather than r“ _', _ :fi _..._me if“. Fred Wesley Freeman its inherent physiological makeup. A third study was set up to investigate. by use of Cl4—labeled simazine. the wide difference in tolerance of red and white pine to simazine. In addition. the effect of the mycorrhizal relationship aSSociated with these two pines was investigated. Two radioassay procedures. autoradiography and counting of plant parts. were used. Results of this study showed the total uptake of simazine to be approximately equal for both red and white pine. The needles of red pine. however. contained approxi— mately three times the amount of (31'4 as the needles of white pine. In white pine the simazine is concentrated more heavily in the roots of the seedlings. while distribution of simazine or its degradation products in red pine is fairly uniform throughout the plantr Since simazine kills by block— ing the Hill reaction during photosynthesis. the reaSon for the greater tolerance exhibited by white pine seems evident. At the time of radioactive treatment. mycorrhizae had advanced only into the initial stage of development on the inoculated seedlings. Even at this early stage of develop— ment. however. the inoculated white pine seedlings contained Significantly less radioactive material than the noninoculated white pines. In fact. counts of noninoculated plants were more than double those of inoculated plants. No apparent differences were noted in simazine uptake . a ' “t 2‘ h'”c between inoculated and noninoculated rcd PING. 139 mlcorrlléll - ',,_’ (-3 I. l. relationship either had no effect on Slmddlne uptake nith 1115 Species or perhaps develops slower 0n {Ed Plne and therefore had.n0t reached a stage where it could influence uptake. ¥ -—- +-. . FACTORS AFFECTING THL" DIFFERENTIAL TOLERANCE OF TRLL SPLCILS T0 HERBICIDLS. PRIMARILY SlMAZlNh By Fred Wesley Freeman A THLSIS Submitted to . Michigan State Univer51ty. in partial fulfillment of the requ1rements for the degree of DfoTlHi (H3 INiILA)S(HdiY Department of Forestry lUnj AC K NOh'L lil) GM EN TS The author expresses his deep appreciation to the many persons responsible for the successful completion of this study. The Graduate Committee have given generously of their time and special skills. enabling the writer to combine all phases of the research into this final form. M; sincere thanks to: Dr. Donald P. WatSon. Professor of Horticulture. who encouraged me to begin Work on this degree. arranged for the necessary leaves of absence and insisted on early com- pletion of language requirements. a stumbling block for So many graduate students. Dr. Stanley K. Ries. Associate Professor of Horticulture. who first aroused my interest in chemical weed control and gave much thought. time. and equip— ment toward completion of the early stages of investigation. Dr. Jonathan W. Wright. ASSociate ProfeSSor of Forestry. Whose assistance with design of experiments. program planning. and techniques of field SCoring have been most helpful and time saving, Dr. Martin J. Bukovac. ASSoCiate ProfeSSor of Horticulture. who gave generously of his time in guiding me through the radioassay procedures performed at Hidden Lake Gardens and on campus. Special thanks are due Dr. Donald P. WhitE. ASSUCiatG Professor of Forestry ENG chairman of the Graduate Committee. who closely :nqmervised the development. organization. and ii m awn-v a . 3v '- ‘ V 1h! writixn: of the complete study. At Dr. unite's suggestion and with his assistance. the phase of the study dealing with the mycorrhizal relationship was developed. The writer is grateful to the Lieigj' Chemical ('orporation of Ardsley. New iork. for their contribution of Eli—labeled simazine. An expression of gratitude is alSo due my wife. Jeanne. and the children. whose patience. understanding. sacrifice. and encouragement contributed much to the completion of this Work. To these and to all others who have contributed to this work but have not been mentioned. I extend my thanks. ,4. & fi—‘fl w: vlt VI TA Fred Wesley Freeman Candidate for the Degree of Doctor of Philosophy Final Examination: February 10. 1003 Dissertation: Factors Affecting the Differential Tolerance of Tree Species to Herbicides, Primarily Simazine Outline of Studies: Major subject: Forestry Minor subjects: Horticulture. Botany Biographical Items: Born‘August 37. 1034. Logan. Ohio Undergraduate Studies: Ohio University. 1U40~1047 Michigan State University. 1047-1040 B.S. Forestry. 1040 Graduate Studies: Michigan State University. 1050—1031 M . S . Forestry. 1051 Michigan State University. 1057—1003 Ph.D. Forestry. 1003 Experience: . , Soil Scientist. Bureau of Reclamation (Bismarck. North Dakota). 1050; Ranger. Ohio Division of Forestry (Hock— ing State Forest). 1031-34; Forester. Ohio Division Of. Forestry (Athens. Ohio). 1054—55; Horticulturist. Michi- gan State University (Hidden Lake Gardens). lunafol: . Curator k Assistant ProfeSSor. Michigan State UniverSJty (Hidden Lake Gardens). 1001 to date. Member: Society of American Foresters ' American Society for Horticultural Sc1ence American ASSociation of Botanical Gardens and Arboretums Xi Sigma Pi Awards: , ‘ I . k Fellowship in Horticulture awarded by the LFgliSn.‘a Speaking Commonwealth and the Garden (lub o :meric . 1003. iv TABLE OF CONTENTS Chapter I. INTRODUCTION 11. REVIEW OF LITERATURE Comparison of s- triazines . Use of Simazine and Atrazine on Woody Plants . Chemical and Physical Properties of the s— triazines . Factors Affecting Herbicidal Action of Simazine . Deactivation of Simazine by Soil Microorganisms Physiology of the s— triazines in the Plant . . . . . . . . I 1—4 1. METHODS AND PROCEDURE Comparison of Several Soil Fumigants and Herbicides in Nursery Seedbeds Weed Control Ratings . . Tree Seedling Injury Ratings Statistical Analysis . Results and Discussion Weed Control Seedling Injury IV. TOLERANCE OF SEVERAL HARDWOOD AND CONIFEROUS SPECIES TO SIMAZINE TREATMENTS Seedling Survival and Analysis Root Elongation . . . . . Results and Discussion Seedling Survival Root Elongation V. THE UPTAKE AND DISTRIBUTION OF C14-LABELED SIMAZINE OR ITS DEGRADATION PRODUCTS IN MYCORRHIZAL AND NON—MXCORRHIZAL RED AND WHITE PINE SEEDLINGS Jl {w Description of Growing Chamber and Growth Medium Treatment with Radioactive Simazine . Autoradiograms and Counting Statistical Analysis . Results and Discussion Autoradiograms . . . . . . . . . . Counts of Radioactive Plant Parts VI. SLNMARY AND CONCLUSIONS LITERATURE CITED APPENDIX Table [u 10 ll l3 l4 LIST OF TABLES Weed control treatments used in nursery seedbeds Tree Species used in nursery weed control experiment . Mid—June weed control Mid—July weed control Mid—August weed Control Survival index of tree seedlings in the nursery weed control experiment Percentage of seedlings remaining alive under DNBP and s—triazine treatments in mid—July Tree species used in greenhouse simazine experiment Duration (weeks) of seedling survival under various simazine treatments Mean counts of C14 in red and white pine Counts of C14 in roots. stems. and leaves of red and white pine seedlings Counts of C14 in inoculated and noninocu— lated white pine seedlings . . . l4 . . . Distribution of C in red and white pine (percentage basis) . . Percentage of C14 in leaves and roots of red and white pine vii 30 40 44 01 03 DJ o4 Figure l U: 10 ll 13 14 LIST OF FIGURES General View of Bogue Forest Nursery showing location of study on soil fumigants and herbicides in nursery seedbeds . . Weed population in nursery seedbeds Extremes in weed control at six weeks after treatment Layout of greenhouse experiment testing tolerance of several hardwood and coniferous species to simazine treatments Tolerance of honeylocust and bur oak to various simazine treatments at 3 months after application Root elongation of Scotch pine at 3 weeks after germination Root elongation of red pine at 3 weeks after germination Root elongation of white pine at 3 weeks after germination Root elongation of bur oak at 15 days Bur oak seedlings 10 weeks after treatment with 4 pounds per acre simazine. Auto— radiogram of bur oak 5 weeks after treat— ment with 3 pounds per acre radioactive simazine Polyethylene greenhouse used for growing inoculated and noninoculated red and white pine seedlings Application of radioactive simazine treat- ments . . . . . . . . . . . . . . . . . . Autoradiograms and seedling photographs of red pine . . . . . . . . . . . . . . . Autoradiograms and seedling photographs of white pine C viii Page 'Jl 5—; U: «L‘- LIST OF APPENDICES Appendix Page 1 Self—absorption curve . . . . . . . . . . . . 70 [.1 Listing of common and chemical names of herbicides and Soil fumigants mentioned in the text . . . . . . . . . . . . . . . . . 80 3 Total weight. total counts per minute. background counts per minute. corrected counts per minute and adjusted counts per minute for red and white pine seedlings . . . 81 ix CHAPTER I INTRODUCTION Chemical weed control is a relatively new field in agri— culture which has received much stimulus since the end of the second World War. The majority of the work done in this field has been in connection with agricultural food crops. Chemical control of weeds in woody plant nurseries has de— veloped slowly because of complications arising from the wide variety of plants grown on a small acreage. differences in the age of plants and by the fact that these plants are peren— nials which may remain in the same location for several years. Becau5e of varied growth habits and inherent differences in their physiological makeup. plants often react quite differ— ently to the same herbicide. thus precluding one treatment over a very sizable area. In addition. the perennial nature of the plants necessitates application of herbicides on the same acreage in successive years. Repeated applications may not allow time for complete breakdown of the herbicides. re— sulting in build up of chemicals in the Soil to levels toxic to nursery stock. AS with many other products. the demand for nursery stock has increased more rapidly than the techniques of pro— duction. Aroused public interest in conservation has tended to increase the use of forest Species by state. federal. and private landowners in reclaiming submarginal agricultural l land. In addition. the trend toward suburban living has en~ larged the demand for both forest and ornamental transplants. Thus number and Size of nurseries has grown steadily over the years to meet the demand of the public. _Since chemical weed control research in nursery management has been very limited. manual methods of weed control have continued as an expensive and laborious operation. Another facet of the problem which often goes unnoticed is the production and use of coniferous stock for forest plantations. when in some instances hardwoods would be more desirable. This has been , brought on by the necessity for almost complete hand weeding of hardwood seedbeds. while some of the weed population in conifers can be taken care of with petroleum and mineral Spirits. Poor survival of hardwoods in forest plantations. due largely to weed Competition. has alSo restricted their use. , Holm (1058) sums up our stage of advancement in chemical weed control practices with the statement. "The great potential of modern methods of chemical weed control in nurseries awaits both intensive basic research and continued field testing.“ . . The initial phase bf work in this investigation was de- signed to compare the weed control capabilities of several 8011 fumigants and herbicides and the effect of these weed Control agents on germinating coniferous seedlings. The most promising chemical. simazine. was then investigated in more detail. Simazine was firSt screened against a Wide variety ”f tree seedlings at different rates and depths of placement. Ru . . Qt elongation studies of several trees were alSo made to determine whether rate of root elongation had any effect on the differential tolerance of tree species to this chemical. The final phase investigated. by use of C14 tracer techniques. the uptake and distribution of simazine in white pine which is relatively resistant to simazine and red pine which is easily killed by this chemical. Red and white pine seedlings. both with and without mycorrhizal inoculation. Were used. (WE\PTER II REVIEW OF LITERATURE It has been estimated that losses to agricultural lands from weeds alone amount to almost four million dollars annu- ally (Klingman. 10ol).i If losses to utility companies. high- ways. public recreation areas. and industrial sites were included. the figures would beCome even greater. The relative newness of chemical weed control is attested to by the fact that in 1055 there were only 135 federal. state. and industrial researchers and 8 state extension workers engaged in weed control work. whereas. in onO the Weed Society of America had over 300 active members and regional weed control con— ‘ferences were meeting annually in four different sections of the? United States. While some work was done in the early 1t2U()’s. the really big advance came with the advent of 3.4—D in lLNJl. Early weed control practices in forest nurseries were largealy’ confined to hand weeding. mulching. or mechanical culti\%1tion where space was adequate. Poisonous gases and steani stxarilization. where feasible. were also commonly used Imefrire 1050 for fumigation of seedbeds. Chemical control in conifkarous seedbeds during this era. and to a great extent now. was; ax:complished with repeated applications of petro— leum Spiifii:s and mineral Spirits. Holm (1038) reports that Urganic clieniicals Were first tested for nursery weed control 4 - en- 5 i . . _ . . “ the I.ake States Region “n 1030. For example. trichloro— acetic acid (TCA) was used as a pre-planting Soil treatment for control of perennial grasses and subsequently 3.3—dichloro— propionic acid (dalapon) and maleic hydrazide alSo proved ef— fective for grass control. Sodium 3.4—dichlorophenoxyethyl sulfate (seSone) was probably the most commonl; used herbi— cide until 1053 at which time the urea herbicides came into usage. both alone and in Combination with seSone and dalapon. Recently. many of these different organic chemicals have been tested in new forest plantations with promising results (White. 1003). Kozlowskiv(1000) reports that hand weeding Costs in forest nurseries are as high as Sl.3SO_lo per acre while TaylorSOn and Holm (1058) cite a saving of S450 per acre over hand weeding of coniferous transplants by use of 3-(p—chloro— phende-l. l—dimethylurea (Monuron) and 3.4-dichlorophenoxy— aceytic acid (3.4—D). In work carried on by Havis (1001). .chill()rO—4. o—bis(ethylamino)—s—triazine (simazine) applied duriiig spring at 3 pounds per acre to lining—out beds with a repxeat application in midsummer. required only one hand weediru; during the season compared to six had weedings for Hm check. Chie rd the newer groups of herbicides is the s-triazines. Considerwible screening and some basic research has been done with simaazine and atrazine. tWo of the more Commonly used chemicals in this group. Their selectivity and long residual. a(:tion are desirable traits which lend themselves \N . g l:- . ell tc) the fields of nursery management and plantation establishment. Since much of the Work to date has been done in fields other than forestry. it will be necessary to transgress into other agricultural fields in order to preSent a clear picture of all factors pertinent to their behavior. Comparison of s—Triazines Many investigators (Friesen. 1058). (Peters. 1057). (TaylorSon and Holm. 1058). (Trevett and Burnham. 1057). (Vengris. 1057) have proclaimed the excellent weed control obtained with simazine when compared with other herbicides. This exceptional weed control is certainly due in part to the long residual action of this chemical (Switzer. 1058). Ries and WatSOn (1057) and TaylorSOn and Holm (1058) found that When simazine was applied at the rate of 4 pounds per acre to litiing—out stock. weeds were satisfactorily controlled thr(n1gh0ut the entire growing season. Noll (1000) and Tal— tflgrt ahd Fletchall (1050). like most investigators. rate 2— ‘hlorw)e4—ethylamino-o—iSopropylamino—s-triazine (atrazine) ‘ . equal. to simazine for weed control. Schneider (1050) re— porfs that deep rooted weeds. such as velvetleaf (Abutilon Theophzwasti Medic.) are more sensitive to atrazine than simaziiie. probably because of the higher Solubility of the former arui for this same reaSon atrazine acts a little faster than sinuaz:ine. On the other hand. simazine gives longer control ()f barnyard grass (Echinochloa crusgalli L.). several SPECIes (d7 I>anicum and crabgrass (Digitaria sanguinalis L.) \\ Q CaUSe ()f its lower Solubility. Since atrazine does have Value as a contact herbicide. it can be used on young Weeds while simazine must be used as a preemergence treatment. Lovely (1053) found granular formulations of simazine as effective as Spray formulations. Fletchall and Schweiss (1050). however. harvested 350 pounds of weeds per acre from a granular application. Compared to 50 pounds per acre from a liquid application. Unpublished work by the writer alSo shows superior weed control from a wettable formulation. ‘ Probably due to limited testing and different weed populations. there is much disagreement among researchers as to the herbicidal activity of many of the other triazine de— rivatives. It is generally agreed that l-chloro-4—diethyl— amino—o—ethylamino—S-triazine (trietazine). l—chloro—J—di- ethylamino—o—iSopropylamino-sariazine (ipazine) and l—chloro- J L)—bis (diethylamino)—s—triazine (chlorazine) are anu>ng the least active of the more Common derivatives. yet Tallwert and Fletchall (105”) achieved 01 percent weed control with .ipazine and trietazine compared to “5 percent control with ttie same rate of simazine. Havis (1001) rates j—chloro— 4.0—Iais (isopropylamino)—s—triazine (propazine) equal to simaziiie .for weed control. 2-methoxy—4.o—bis(ethylamino) s—triaziaie (simetone) is rated slightly less effective by Jansen et: a1. (1&3? . while 3—methoxy-4.o—bis(iSopropylamino)— s—triazirie (prometone) and 2—methoxy—4—ethylamino-o—iSopropyl— amino—s—tr‘iazine (atratone) are rated by Noll (lOOU) as having an activit:y intermediate between simazine and chlorazine. ~Just as the derivatives Show a difference in their PhYtutoxic effect on weeds. they alSo show a difference in selectivity on crop plants. Many small fruits. tree fruits. ornamentals. and forest trees have shown a tolerance to simazine and atrazine depending on dosage used. time of ap— plication and other factors (Anonymous. IUnO). (Anonymous. onl). Larsen and Ries (ono) used simazine on young fruit trees at rates as high as 8 pounds per acre with no resultant injuryy (firigsby (lfllfii) has fknnui that Simazirwa.is also a good algacide. At 3 p.p.m. simazine was lethal to mixtures of filamentous and unicellular green algae and this toxicity persisted for periods up to six months. whereas copper sul- fate and Sodium arsenite produced good initial kills but re- growth was found three to four weeks after treatment. Use of Simazine and Atrazine on Woody Plants { A number of'investigators have screened various woody Spngcices. both ornamental and forest. against Simazine and atrazaine when used alone and in combination with other chemi- cals. Ries et al. (1058) found simazine to be the best herbiczicle of the nine tested against four Species of ornamental lining—«int stock. A repeat application at 4 pounds per acre durhig tiie second growing seaSon still caused no injury. Runge (lfllo()) reported no injury when Simazine and atrazine were apniliemj to numerous Species of established nursery Stock. TaylorScni aJid Holm (1058) report no injury to 3-year—old Doug1a5_1 ir (Pseudotsuga menziessi 'Mirb.J Franco.). Scotch Pinus sylvestris L.). Austrian pine (Pinus nigra Arnold). white Spruce (Picea glauca Moench., Voss.) and blue spruce (Picea pungens Engelm.) when treated with simazine at 4 pounds per acre. In windbreak plantings with ten common coniferous species. Bagley and Myoshi (1050) found no ap— parent chemical injury from 4 pounds per acre simazine treat— ments with the exception of a sandy loam Soil on which the survival of eastern redcedar (Juniperus virginiana L.) and red pine (Pinus resinosa Ait.) was lower than the Controls. They indicate that high rainfall and shallow rooted planting stock may have been the reaSon for injury with the red pine. Trees in control plots were Soon overtopped by weeds. vigor and growth were impaired and survival was generally lower. Holm et al. (1057) report Slight injury to seedling trans— Plants of Scotch pine with a treatment of 3 pounds per acre (fl? simazine. In this case the spring weather was very wet. In ivork carried on by Ahrens (1001). the tolerance of hemlock trgUlSIJIantS to simazine was increased greatly by delaying treatnnent for a longer period after tranSplanting. It was alSo ncited that tolerance to this herbicide alSo increased with tiie age of the tranSplants. Winget et al. (1000) ar— rived eat the same conclusion in connection with red pine. hiox’ing from the nursery to the planting site. the C0mP€titim>n is intensified between the transplants and the weeds fRJr \vater and nutritive elements. JohnSon (1000) states thélt as we continue to utilize the richer sites. weed prcnalenns seriously limit the early growth of tree seed— llngs- fie c:ites as an example. the serious grass problems 1 (7) V&\;Ch eXist on the Spruce planting Sites in the Lake States. \Vpite (1”00) has demonstrated on these spruce sites signifi~ Cantly higher survival with chemical weed control as compared vvith no weed control, According to White. "The effectiveness (if the simazine weed control in increasing survival. growth aJ1d foliage color of spruce on the test sites commends the axjoption of this technique into regular silvicultural px'actice.” Kuntz et al. (1000) have had similar experiences ()f' increased survival with outplantings of pines and Norway 5;)ruce (Picea abies 1L.: Karst.). Hovind (1050) has shown SLlrvival percentages in 3-year—old red pine to be 50 percent \vi‘th 1—1/2 pounds of simazine plus 7—1/2 pounds of dalapon [381‘ acre. 43 percent with 3 pounds of simazine per acre. as (:onipared to 17 percent survival in the furrow with no clieniical treatment and a complete loss in those plantings wrnere no furrow or chemical was uSed. Jokela et al. (1001) lia\we demonstrated increased growth of hardwood transplants by usiJig simazine immediately after outplanting. Chemical and Physical Properties of the s—Triazines The triazines are heterocyclic nitrogen derivatives. tneanixxg they have a ring structure composed of atoms of dif— fererrt kinds. If this ring is o—membered with two or more nitrogen atoms in the ring. it is known as an azine. The structural formula for simazine is: an NH St:ructurall . atrazine differs from simazine in that (‘3H7 group is attached to the fourth carbon in the ring in pfilace of the NH C)H3 in simazine. The technical material in b()th simazine and atrazine is a white crystalline substance \vi th low Solubility in water. Simazine at 5 p.p.m. has the 1(HVCSt solubility of the better known s—triazines while sirnetone at 3300 p.p.m. has the highest. Solubilities of some ()f the other triazine compounds are propazine at 3.0 p.p.m.. €311<>ra2ine — 10 p.p.m.. trietazine - 30 p,p_m.. iapzine _ 40 I).p>.m.. atrazine — TU p.p.m.. J—chloro—J—methylamino—o-iSo- {arcqaylamino—S-triazine (G—30030) - 300 p.p.m.. prometone - and atratone at 1800 p.p.m. (Richards. lUQU). TSo p.p.m.. Tfiie (iecomposition of simazine occurs as a first order re- acrtitni. meaning that under comparable Conditions the same 13erw:er1tage of the original rate will be found in the soil at a ggivezn time. regardless of whether the rate was a high or ltnv (Hie (Burschel. 1001), Factors Affecting Herbicidal Action of Simazine Simm?td the factors affecting herbicidal action of sinnazirie are the amount of precipitation. fixation by Clay J‘ 13 afld,‘3rgalkic matter. depth of placement. time of application. soil ‘fflnperature. and to Some extent the pH of the Soil. igurnside and.Behrens (1001b) reported that increasing soil temperature. within limits. caused increased simazine ttixicity to corn. in another paper. Burnside et al.(onla) ireported that high temperature and to a lesser extent low pfli (pH 4) caused a Significant deactivation of simazine in uwlter suspensions. JHowever. the very high temperature ncecessary. indicates this would not be a significant factor iri the field. Maximum results with simazine are usually obtained when ttris herbicide is applied during early Spring before active grwawth begins. However. Chadwick (1058) obtained excellent \veenj control even after eight months from the time of appli— <:at ion in November. Havis (1001) alSo secured excellent <:orttrol of quackgrass (Agropyron repens L.) in established tiurwsery stock from fall applications of simazine and atrazine at 21 rate of 5 pounds per acre. Lovely (1058) found that working granular Simazine into the Soil does not improve its efffn:tiveness. Results of work carried on by Freeman agree xvith ‘this finding. When simazine in both granular and wettable fkwrm.vwas worked into the Soil and applied as a surface trewitment. the surface treatment in wettable form gave the ‘best \veed control. Additional unpublished work regarding weewi control as affected by depth of simazine placement. was cxrrried on by the writer in l“53. Granular simazine was 1Freeman. F, W.. 1000, Unpublished data. Michigan State (University. 13 ¥fifilCed»Eit the rate of 4 pounds per acre at different depths in tr“? Soil mixture of one gallon tin cans. Four months after treatment. almost complete eradication of weeds was obtained from the surface application. The herbicide was ()f some value when placed at a depth of 1 inch. but when {)1aced at a depth of 3 inches and belbw. no weed control tvas evident. This does not agree with the findings of l5eddema (1958). who killed test weeds when simazine was ipalaced from 4—13 inches below the Soil surface. Simazine leaches from the Soil surface very slowly. v 6 Btirschel (1001) found that even after application of 4 inches of~ water. 85-01 percent of the herbicide still remained in ‘thé? upper inch 0f Soil.. Working with C14 —1abeled simazine aruj atrazine. Montgomery and Freed (lUSO) found maximum penaetration of Simazine at 7 inches and atrazine at 13 inches. af"ter 10 pound per acre treatments of these herbicides were leuached with 13 inches of water. However. maximum concen— trwation of simazine was at the 0—1 inch level while maximum C(nicentration of atrazine was at the 7—8 inch level. In unguiblished Work carried on by the writer. monthly bio— £3558} tests were made to determine the rate of leaching and ‘resitiual action of simazine under field conditions. Soil sanuales were taken at monthly intervals from an outdoor thirsery experiment in which simazine had been applied at l. 3. auuj 4 pounds per acre. These samples were taken at the syiil surface. at a depth of 1 inch and at a 3—inch depth. (lunnnber (Cucumis sativus L.) seedlings were then germinated .1, In if? i 14 {YHESG‘ Soils and number of dead seedlings was recorded. All tffiits were replicated four times. Results showed that the 1 and ’ pound applications never moved below the 1 inch c—4 level and that at the end of four months all simazine had laeen tnnflxen down. .hi additicni. the 4 txnnui treatnmnit never (eliminated all of the cucumber seedlings at the 3 inch depth ciuring the four months that the bio—assays were being run. [Jindings of Burnside et al. (1001a) and Derscheid (1058) alSo sittest to the slow movement of simazine through the Soil pro- f‘ile. Simazine at 5 and 10 pound per acre rates has remained ir1 some soils for two growing seaSons at levels toxic to geerminating seedlings (Sweet et al. (1033). Low Solubility aruj consequent slow leaching certainly contribute to the 1(H1g residual action of this chemical. On the other hand. sinuazine and atrazine have been shown to lose their toxicity of ’ pounds per acre within eight weeks. under condi— I—l at :rates titnis of high moisture and summer temperature (Switzer and Ilatuser. 1000). Stroube and Bondarenko (1000) found through ()at laio-assays that twelve months after application of 4 rx>uncfs of simazine per acre. the simazine equivalent in the kM-B ixach level was 1/3 pound. 1/8 pound in the 3-0 inch \ le\wal. and none in the 0—0 inch layer. Deactivation of Simazine by Soil Microorganisms :\S mentioned earlier. soils high in organic matter and/ t)r cliay content caused reduced simazine phytotoxicity as Ompared to Soils 10w in these components (Burnside and C, BehrenS. 1001b). Sheets and DanielSon (1000) investigated in detail the effect of Soil organic matter. clay content. (:ation—exchange capacity and pH on the phytotoxicity of simazine. Soil organic matter appeared to alter the initial t()xicity of simazine most. They alSo found that in contrast t<3 3.4—D. repeat applications of the s-triazines are inacti— vzited in the soil at about the same rate. Apparently the Sc)il microorganisms capable of inactivating 2.4—D increase vvi th repeated applications of this herbicide while those n1ic:roorganisms which inactivate the s—triazines are passive -.in action. i.e.. organisms utilize them but not selectively ()r preferentially. BurSChel (1001) states that the de— Ccnnposition of simazine in the soil is closely related to the anubunt of humus present. In fact. without humus. no decompo— si tion will occur. Pure loess soil which contained no humus wajs analyzed for simazine 3—1/3 months after being treated witfli 2 and 4 p.p.m. and found to contain all of the original treatmentl He'found that the greater the amount of humus. ancl thus microorganisms. the more rapidly simazine is de— actiywated in the soil. Further study showed that lowering the txemperature from 35°C. to 8.50C. caused a Sevenfold decrease in the rate of decomposition. Burschel-attributes this decrease to the fact that microorganisms are alSo af- fected by lowering of temperature. This would indicate that fall applications of this herbicide will react much differently from those made in spring. Burnside et al. (1001a) found that; SO11-microorganisms deactivated Simazine. but very 510w1)’- Most of the deactivation occurred after the fourth month. Five microorganisms that were able to subsist for three months in media containing simazine as the sole Source (3f nitrogen and nearly Sole Source of carbon were iSolated zand identified as Penicillium pupurogenum. Aspergillus ustus. 311d three Streptomyces species (Actinomycetes). However. tilese microorganisms did not deactivate Simazine in Solution Ctiltures during a 30 day incubation period. According to Rezid (1000). a group of soil bacteria. the Soil diptheroids (C?orynebacteriaceae) have been found to remove the s—triazines frw)m the Soil. Observations by Guillemat et al. (1000) em— pruasize the existence of fungi capable of metabolizing sixnazine and utilizing the nitrogen of this herbicide. It apnaears. in addition. that this degradation is tied to the atnindance of carbon in the medium. The fungi listed as renaponsible for this degradation were Fusarium oxySporum. Ibisarium avenaceum. Penicillium cyclopucin. Penicillium larnwseo—coerulem. Cylindrocarbon radicicola. and Stachybotrys species. In contrast to deactivation of simazine by telluric tnicrcxjrganisms. Castelfranco and co—workers (1901a) have fourui that calcium polysulfide. a pesticide and Soil cor— rective. also has the property for decomposing Simazine. Because of its safety and relatively low cost. they feel that it could be used to hasten the breakdown of s—triazines in S()il. 17 It lias been generally established that simazine has no deleterdxnis effect on the Soil microflora. even when applied at extremely heavy dosages. Burnside et al. (1001a) measured carbon dioxide evolution and found it unchanged 30 days after simazine was applied at rates up to 400m p.p.m. Nitrate fformation was not impaired even by larger applications of this herbicide. After applying 3oo kilograms of simazine [Der hectare. Guillemat et al. (1000) observed only insignifi— <:ant changes to the microorganisms. On the other hand. (Haandra et al. (1000) observed depressed carbon dioxide exunlution in simazine—treated soils. the percent decrease genierally being greatest at 38 days and decreasing there- afiter. Physiology of the S-Triazines in the Plant Typical symptom of Simazine toxicity is the chlorosis -wt1ich starts at the leaf tip and progresses along the margins t() the base of the leaf. Necrosis occurs in the chlorotic arewi and chlorosis spreads to the entire leaf. These synujtoms in the plant are a result of blockage of the Hill renactrion. or the ability of chloroplasts to break down water intt) hydrogen and oxygen in the presence of light and iron (Sctnaeider. lUSS), Ashton et al. (1000) have demonstrated \vitrl excised leaves of kidney bean (Phaseolus vulgaris L.) that: the degree of inhibition of carbon dioxide fixation incrwnases with higher concentrations of the herbicide and longuer exposure time. Roth (105%) has also Shown with W leaves that assimilation in Simazine Solutions is inhibited, Work by Moreland et al. (1050) showed that glucose S’upplied to barley plants through Severed leaf tips kept plants alive and growing in the presence of lethal concen- trations of simazine for more than two months, Experiments by Gast (1058) confirm these findings. The chloroplasts of starch free Coleus Bluemi leaves kept on a Solution contain- ing sugar and Simazine were able to form starch again. More— land found that Simazine appeared to have a similar effect on the activity of both barley and corn chloroplasts even though barley is quite susceptible to this herbicide while corn is very tolerant. Therefore. he concluded that the mechanisms which control selectivity must act before the herbicide reaches the chloroplasts. Montgomery and I-‘reed (1001) and many other investigators have shown that the corn plant is able to degrade the s—triazines and readily meta— bolize these compounds. Since heating of corn sap destroys its ability to decompose simazine. Roth (1057) suggests that the resistance of corn to Simazine is due to a thermolabile system. perhaps fermentative. which can transform this sub- stance into compounds devoid of biologic action. (‘astel- franco and co-workers (1001b) state that the action of simazine toward different species of grasses suggests that non—enzymic detoxification reactions catalyzed by small organic molecules may play a major role in determining the resistance or susceptibility of a particular Species. Davis et a1. (1050) have demonstrated through the radioactivity present in leaf samples that simazine is absorbed readily 1o \ 0y I ‘Lh . , . . e I‘Uots of both corn (Zea Mays L.) and cucumber ((ucumis 4¢ati r . . . . \‘15 L.,). Honeumnr. radioactiyitgl\was observed nuuni sooner lh Qiunnnber than in corn and simazine or the Cl4-labeled de— gradation products moved more readily in cucumber than in corn. In addition. Ragab and McCollum (onl) have proved that both resistant and susceptible plants deCompose simazine. The fact that cucumber metabolized simazine at a more rapid rate than corn dispels the suggestion that toxicity is associated with inability to metabolize the herbicide. They alSo found that cucumber plants growing in nutrient moistened glass produced adventitious roots on the stems. indicating that the herbicide is toxic to the roots. Foy (1001) has found that Some of the triazine compounds accumulate in the lysigenous glands of cotton (Gossypium). Since substances deposited in these glands are apparently removed from circu— lation at least temporarily. he postulated that such accumu— lation may constitute a protective mechanism against these heljiicides in normal glanded cotton. Studies with genetic— 2,11}? glandless varieties have thus far supported this hypo- .fljessies. Another important factor which has been discovered DY IZr>tri (lUnl) is that in certain cases corn absorbs relat:i\/ely less Simazine than other plants. I3rom these investigations. it becomes evident that diffeifenfit resistant plants have different mechanisms for neutraalrizing or minimizing the toxic effects of the triazine ComeUnd S . 1. . CHAPTER II MLTHODS AND PROCEDURE ; The excellent. long—lasting weed control obtained with simazine and atrazine in preliminary_investigations. prompted a more detailed investigation of these herbicides for use in nunsery seedbeds. It was decided that the logical starting poflnt would be a comparison of these s—triazines under field conditions with other recently developed herbicides and soil fumigants in addition to those in common usage. As an ad— junct to the field work. a greenhouse experiment was set up to determine the reaction and tolerance of a wide range of germinating tree Species to different rates of Simazine ap- plied both as a surface treatment and intermixed with the Upper layer of soil. The differential tolerance exhibited by the tree species in ‘the above mentioned experiments. in turn led to the third Fflaatse of work. This study investigated by use of ClJ-labeled sijnaizine. the uptake of C14 by red and white pine seedlings. anci. in addition. the effect of inoculation with mVCorrhizal J furtgui on this uptake. Comparison of Several Soil Fumigants and Herbicides in Nursery Seedbeds 'Fhis portion of the study was set up in the Bogue Forest Nurwsevfy’ (Figure 1) located on the campus of Michigan State 30 .mpmnpmom may ob Hwaamuma sad nUfins moon ucmaamcmuo mozuam powwow» oceumswm 03¢ may Mo :ofiu ufipcoo meow one: on“ ouoz .mpmnpmwm >ummuac :fi mvpfluenumn can macawflesw HflOm :o >03um Mo cofipwuoH wcflzonm >ummusz omwuom wswom mo Bwfi> Hmumcmw .H musmfim 21 'Table 31. Weed control treatments used in nursery seedbeds. a—-——_____l Days applied Treat. Rate/acre before or NO. Treatment (active) after seeding 1 Control —— —- 3 Handweed -— . As needed 3 Stoddard Solvent 25 gal. 0 times during seaSOn 4 Methyl bromide 870 lbs. 14 days before 5 EPTC 4 1b. At seeding o DMTT 280 1b. 25 days before 7 SMDC 100 gal. 25 days before 8 Chloropicrin 35 gal. 14 days before 0 Ureaformaldehyde 85 137 gal. 20 days before 10. Ureaformaldehyde 85 72 gal. 30 days before plus allyl alcohol 50 gal. plus ethylene dibromide 8.4 gal. 11 Ureaformaldehyde SS 127 gal. 30 days before plus simazine 4 1b. W 13 DNBP 7 lb. At seeding 13 Simazine 2 lb. W At seeding 14 Simazine 4 1b. W At seeding 15 Simazine 8 lb. W At seeding lo Simazine 2 lb. G At seeding 17 Simazine 4 lb. G At seeding 18 Simazine 8 lb. G At seeding 10 Atrazine 4 1b. G At seeding ‘jU Atrazine 8 1b. G At seeding 73 v“ 1 \r er‘Sity. The soil type is Hillsdale sandy loam. Twenty treatments were used. consisting of Soil fumi- gants and herbicides tested both alone and in combination (Table 1). Each treatment was sown to 10 coniferous species. Treatment plots measured 4 feet by 0 feet and each plot was separated by a 3-foot isolation strip. The tree seed was sown in rows 4 feet long and / inches apart. All treatments were randomized within the block and replicated Six times. The seedbeds were prepared quite early during the Spring in order to allow a safe waiting period between application of Soil fumigants and Sowing of the Seeds. Table 3 lists the 10 coniferous Species sown to each treatment and the approximate number of seeds Sown in each row. The tree :Seeds were sown on May lf and seedbeds were-covered with slat :Eshading during germination and early growth of the seedlings. \fifiater was applied as needed during the growing SeaSon by an gaverhead sprinkling system. 'I‘able-Z. Tree species used in nursery weed control experi— ment. Approx. No. of seeds (Common Name Scientific Name sown per row _\\\’__g B .alsam fir Abies balsamea (L.) Mill. 3.0 Vi lute fir Abies concolor (Gord.) Engelm. 13/ lituropean larch Larix decidua Mill. ooo Tlorway Spruce Picea abies (L.) Karst. 430 \Yhite spruce Picea glauca (Moench.) Voss. oOO cfack pine: Pinus banksiana Lamb. 000 F‘sd pine Pinus resinosa Ait. 303 Ira). prine Pinus strobus L. 405 5 ME . . . . (é ~h. p>1ne Pinus sylvestris L. 340 0(7. ‘)t(./ —f. ' ',_‘ . (N. {{j x 1115 1r Pseudotsuga men41CSS1 ”lirb.) r.( “3 Franco. c? I--__ \\i Q :) " -ii1_£iflltrol Ratings Periodic weed counts were made during the growing sea— SO“. These weed control ratings were made at weekly intervals during June and semi-monthly during July and August. The weekly ratings were divided into seven categories based on the number of weeds present in the area between two rows of seedlings (1.0 sq. ft.). The seven categories are as follows: Grade ' Weeds per l.U Square feet 0 1—3 4—? 0—13 10—30 51-100 100 plus 0 UIJ—(Nlul—“Q J During July and August it became more convenient. be- <:ause of denser weed populations. to rate weed control on the :Fjercentage of plot covered by weeds. Eleven categories were Cjesignated as follows: Grade Weed coverage in percent 0 O 1 1-10 2 11-30 3 31—30 4 31—40 ) 41—30 0 51-00 7 01—70 5 [1—so 0 til—U0 10 01—100 .7be uwwnj control grades were set up as indicated above in axfdfl' tc) normalize data and eliminate need for transformation ex“ )r t() analysis. Convenience in ease of computation was 1L, ‘3k 50 a .factor. "9"" .' 35 'Yr . . T‘::E~S%:S§11ng Injury Ratings 'The coniferous seedlings were checked periodically to dEtermine the effect of the soil fumigants and herbicides on their germination and survival. Injury ratings were deter— mined by recording the number of live seedlings per Species. The ratings were divided into six categories as follows: Grade No, live seedlings per row 0 1-10 11—30 31-100 101—300 300 plus U‘IJd-LAzchI—‘C Sis in the weed control ratings. grades were defined for Aconvenience of computation and to normalize data and thus ¢eliminate need for transformation prior to analysis. :EStatistical Analysis Each set of weed coverage or injury data was subjected t:o analysis of variance. using plot means as items. For eeach analysis the degreeSof freedom were as shown below: Source of Variation Degrees of freedom Treatment 19 Block 5 Error 05 Total 110 Results and Discussion ”feed (Jon trol V— EVEaed Species found on control plots during the course (2 . ' “(5‘ tile gzroW1ng seaSon were: Agropyron repens (L.) BeaU\u K . qudfn‘ grass). Amaranthus retroflexus L. (redroot pigweed). PEHDYOSia artemisiifolia L. (common ragweed). Capsella Bursa- Efiélgiié (L.) Medic. (shepherd's purse). Chenopodium sp. (lamb‘s quarters). Digitaria sanguinalis (L.) Scop. (hairy crabgrass). Lamium amplexicaule L. (henbit). Oxalis europaea Jord. (European Woodsorrel). Polygonum persicaria L. (Spotted knotweed). Portulaca oleraceae L. (Common purslane). and Stellaria media L. (common chickweed). Although weed control ratings were made many times during the growing seaSon. the results of three equally Spaced ratings present a clear picture of the findings. Jigure ’ .4 gives a graphic presentation of weed control at r—mid—June. mid-July. and mid-August. After the middle of r'TAugust all treatments had ceased to give effective Control EELnd no further weed ratings were made. Tables 3. 4. and 5 5;.how the correSponding analysis of variance data for these ) a. . t;hree periods presented graphically in Figure The wide range of weed Control obtained by the variouS t reatments is shown in Figure 3. At six weeks after treat- nlemt most plots containing either simazine or atrazine were F’f‘actically weed free. In direct contrast. the weeds in the u yeaformaldehyde plots were much taller and healthier look— i .ng than those growing in the control plots. In this experiment no appreciable weed control was ()btain6d from Stoddard solvent. ureaformaldehyde. 3 5- dQ-methyitetrahydm 1.3.5 2H thiadiazine—Z—thione (DMTT). . y '. 5?; , n1 niethyl dithiocarbamate (SMDC). trichloronitromethane d1“ .. I‘lorw)p>icrin). ethyl N. N—di—n propylthiolcarbamate (LPTC) .mpmnpmwm summon: me :Oeomasaoa pmwz .m enamem ea 9— a— - o_ m— e. n— N— —— 9— a Q ~ g m c n N — e a .................................................. s -2 w 3 a V m a A m... . 8. 5.83.9: 292428 So; u m I. a H m a 3 0 S S ....... -, m 8 an 52:92 £92.53“. cum; 8. £2.92 £22.58“. Sm; wi 4—— le GGV89)SC|33M‘ON .LHZCum poms pends moomfimon pomzpcmc we sceoomco 30H >Hm>fiomHmn been .ommu mmcwu bandpass m.cuo::Q >2 pwcflEumomp mm .pcmuwmwfip >Hozmoem«:mfim one mafia w >p pooooccoU as: mocmeumoop HHnuo moan .Hmw om Horcoam H>Ham mafia 9H.v .Hmw no mU>LoUHMEncwmmn3 CH oa.e I: mpomzpcm: M mm.v .QH v . 09mm m oo.e .Hmw mm pagodaccoaeo x oo.e .Ham sea oo2m u mx.v .Hmw mm ocm>acm.onmppcom m cc.m .nH oxn page a mw.m .Hmm “NH mp>£mpam5ncmmmu3 . 3 $0.0 In Hohuccu H Ho>mH fl Ho>ma 8m HccfiomHsoom Am>woomv peoEommuH .32 imocmoflmflcmwm poms cmmz o~om\womm .owmuh . wagoamaamLm . “dill é .w mfigmb .chscso new: meswipwz 2‘?” w 7.3- *- /.I/‘l(‘ .omto omens bandpass m.:mo::: an UoCMEumamp mm .oconoduwp >Hacmofl~ecxflm mom ecwfi a we pooomCCCU p3: mocmeomooo HH<1 .omwnmioo new: 2:: maozsox :a pee mwmno>oo Utes fl: mamsvt 3 ”mpooz >2 Umum>3o Head we “Coupon :: pmmmp mmcmomz H , _“ 22.9 -- ommzocm: o 2:.H 3 .ga x vcwmmeam xa U ::.a 2 .SH x mammaEam ma " 2:.H 2 .2H e mcfimmEMm ea . mm.a 3 .2H s mcamaeam mafia . .Hmm oma op>chHmEucwmouz Ha Ax.a 3 .ga x meanmuae :o . :m.m 2 .2a w acquaeam _ ea _ mw.m 0 .za 4 meawmas< :H cc.m 0 .2H d mCMNmEflm ha _ “ :H.v .2a a maze Ma 22.: 0 .2a m ocamaeam 2H w 2:.“ .2a a aha: m . 4 :2.“ .na aux aspects Haebmz 4 ; mn.x .Hau mo scm>acm ecaeecam m m .Hmu w.r opfiECCLfiU ocoascom mafia l .me om HCLOUHm H>Ham mafia ::.:H .Haw we weaeweaaeCcdmmc: :a _ 32.:a .ad% and meaemsamsacommu: : _ 3:.3H .Hem mm casufiaccoaeo x co.:a Ham yea oozm u A:o.3a .nffi cxm. HA;£; c ::.:H -- accocso a Ho>mH 9H Hm>ma Wm acofiomHSQOQ Ao>«bomv ocmeoaonk .32 .Iltimocmowmflcmflm poms :moz ocom\mamz .owmce .HQUSPmaamam El ItIllllllrlllllll\)fi'r7\\. illlllllllllllll\\\ll\\\\\\ . .. Lanfiw HCLQCCU 309.3 .AH3H1\~U.~—2a “r. .Hmmo mace» wHQHoHSE m.:mocsg an UmcHEumump mm .ocoumHqu >HoconchmHm mum mcHH m xn pmuom2:0o no: mocoeomouo HH<1 .mmmum>oo pom: HCOH mHmzdm, :H pcw ammuw>co pom: fl: mHmsco c “memos >n poom>co HOHQ m: acmoumo :0 women mmcHooz H cc.H .. obesecmz m cm.m 2 .2H m mcHNasam mH so.e o .nH x mCHNaEam 2H oc.m 3 .DH e mcHNmeHm eH cc.m 3 .nH a meonmeHm mzHa .Hmw hNH mUHLoUHmEucmmmn: HH mm.o o .QH x mcflwaca< . an mx.h 3 .2H m mcHNmeHw MH nn.w .QH h . mmza NH 59.: 0 .pH e mcHnmuo< 3H . 05.: u .QH v . . . ocHNMEHm h 20.3 o .9H m ghmw.. mcawmeam :H w mx.: .9H s ..- . w.. oeao m nx.3 .DH cow oUHEoHn H>£Ho2 v mm.c .Ham Cw acm>acm ncaeucsm n .Hmm e.x opHESuQHp mcmH>Low mzHo .Hmm cm HCLCUHN H>HHm msHQ oo.oH .Hmm we mpxcmpHMEucmmmu: :H ca.cH .Hmm “NH anaemoHaEucoamu: : cc.cH .Ham mm spoofiacucaeo x . oo.cH .Hmm 39H oozm k . oc.cH .QH oxq eezo : cc.cH It: Hohocou H Hm>9H 3H Ho>oq 3m HcoHomHsocm nm>Hoomv ocoeommoe .cz ioocmonchHm poms 2mm: mood\ouwz .ommue meoHomHumom “It! 1% , . . rUHQNrH as om3m3uH pH no N azoeammuo echo scocmuwHU stcmoHdmcumm .Ho>oH Pm no N ocoeomooH Esau ocouodqu >Ho:moHuchHm .AWUDHH msHo :2m2m .Ammoco 22nuH2H2w .HmmocH 22H-Hm2m .Hmooua 2m-HH2o .Hmmmua 2H-H:H .Hmmvcd 2::H #2. xv. #2. H2. 9:. mH.H MH.H Ho>oH 9H .:.m.o Ho. 2m. 2w. :2. no. or. mm. Ho>oH we ::.2 ::.2 22.: mm.2 ::.2 ::.2 ,2:.: H: ex: ocmnmua< 2n 92.2 ::.2 ::.2 ::.H mm.: :H.2 22.: A: we: mcHNmua< :H no.2 ::.2 22.: :m.: ::.2 ::.2 22.: Ho v.2 mcHumemm xH ::.H 22.2 29.2 2H.H 9H.: .mm.2 . 22.: As we: mcHNaeHm uH mm.m :m.: :m.H .wx.H 22.: 2H.: 29.0 AU an: ocHNweHm 2H CH2 ::.2 ::.2 22.: ::.2 ::.2 22.: Hz was ocmmmeHm mH :m.: 22.: mm.2 2H,: 22.: ::.2 ::.2 A3 he: mcHNmeHm 1H ::.H ::.2 ::.H cc.H 22.: CH.: 2m.2 A3 an: mconmeHm mH ::.m MI.H mm.m ::.N oH.m ::.M no.0 mmzo NH H2 av: mcHNmeHm mzHo ::.2 22.: 22.2 ::.2 ::.2 22.: 22.: mosemonechmou: HH . opHEooan ocmH»:oo mzHo Hasson H>HHm msHQ CC.m so.m, 0H.H.. Oo.m. so.” Grim 00.? DU.»LmUHmEuCMNQHD CH 4 mx.m oo.n :o.m oo.m mx.H :H.M co.m op>sopHMEHOHMon3 2 3 mx.m 5H.n o:.m ::.M oo.H om.m 22.N :HnoHQOMCHQU x ::.w 2m.m so.m c:.m mm.w oc.m cm.n oozm h mm.v 2m.m mm.w 2m.m 9H.w wm.m om.m FEED : or.: ::.H mn.m cm.H oH.H mm.H oH.H Dean m mm.m 9H.n oo.H ::.n 2e.H oo.H mx.2 modes»: Hseomz e :m.m nx.q 2m.m oc.n 2m.m :m.o mm.n oco>Hcm oumoocom m OO.M OH.” CHIN M7,.” Do.m. CH.m. OH.M UmwBUEMI N; ::.v :m.n 9H.m mx.n oo.H mn.m :m.m Hanocco H 5m mm. mm m a .m w... .m a. mm. 2.53:. .3 I . . _. w. m m m m w n. w p w w w m .aamce B a 9A a D S U. _ \ moHoomw book \i < .seoemomaxm Hcoacco 1IIIIIIr1II1tItI::Ill||||\\\\\\\|\lflmmmw H coma spawns: and ed muewHemmm met. a: >u3m .: t xoUCH-Hm>H \ \j7y this treatment. In contrast to this. the combination x;reatment of ureaformaldehyde plus allyl alcohol and ethylene dibromide increased the number of tree seedlings over those found in the control with all species except the red and white pines. The increase in jack pine. Norway Spruce. and Douglas—fir was highly Significant. due to the stimulating effect of allyl alcohol on the growth This increaSe may be of nursery stock (Wilde et al.. 1050). All of the remaining treatments which gave better weed and various s-triazine treat- ccnatrol (methyl bromide. DNBP. Methyl rnerits) alSo damaged the tree seedlings more Severely. brxnmide and DNBP were not as severe on seedlings. however. as sirnazine and atrazine. With all species except Douglas—fir. Seeedling death in methyl bromide plots was significantly liigzher than controls. DNBP shows definite promise as a herbicide which will gi" e good weed control during the early part of the growing Seat Son with a minimum of damage to the germinating tree Survival of red pine and Douglas—fir was not se€‘