THE EFfiECTS GE 3‘ 4A: 5.? cm I‘wexmzaw SMQRTLEAF PENE SLEEQUNGS EN 'FHE GUACH PEA MOUNTAENS OF ARKANSA§ Thesis for “19 Degree of M. S. MICEIGRN STATE UNEVERSITY Edwin Richard Lawson 2960 LIBRARY Michigan State University THE EFFECTS OF 2, 4, 5-T ON TWO-YEAR-OLDSHORTLEAF PINE SEEDLINGS IN THE OUACHITA MOUNTAINS OF ARKANSAS BY EDWIN RICHARD LAWSON AN ABSTRACT Submitted to the College of Agriculture of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Forestry 1960 Approved 6;. Wm Edwin Richard Lawson ABSTRACT Much of the land area of west-central Arkansas is characterized by considerable amounts of undesirable hardwoods on areas where shortleaf pine is grdwing or has grown. All too infrequently, a dense stand of young pine seedlings becomes established beneath the hardwoods, following good seed years, and subsequent growing seasons with adequate, well-distributed rainfall. Foliage spraying with 2, 4, 5-T and related compounds has shown much promise in con- trolling undesirable hardwoods, but information on the effects of such spraying upon young pine seedlings has been uncertain. The effects of spraying upon these seedlings may be the deciding factor in determining whether to use a foliage spray in preference to a single-stem treatment for controlling undesirable hardwoods. A study was carried out in 1959 to determine the effects of foliage spraying with 2, 4, 5-T upon two-year-old shortleaf pine seedlings. Spray application was made in the early growing season and in the late growing season, utilizing one concentration only. The study employed a randomized block design with three replications of two spray treatments and two controls. Each of the twelve study plots was one-half acre in size. Pine seedling inventories were obtained from ten one-tenth milacre subplots in each of the twelve plots. Seedling inventories were made immediately after spray applications. Edwin Richard Lawson Mortality of pine seedlings occurring on plots sprayed in the early growing season as well as on plots sprayed in the late growing season, was statistically compared with that on the control plots. An analysis of variance showed that both of the spray treatments resulted in highly significant mortality of pine seedlings, compared to the natural mortality occurring on control plots. No significant difference could be demonstrated between the results of the late- and early-season spray treatments. Natural mortality of pine seedlings on the early-season control plots was greater than natural mortality on the late—season control plots. Natural mortality is greater in the early part of the growing season than in the late growing season, after the seedlings have hardened off. It may be concluded that foliage spraying with concentrations of 2, 4, 5-T that are effective in killing hardwoods will be likely to result in the death of considerable numbers of pine seedlings also. However, if the number of pine seedlings established on an area is large enough, perhaps in the magnitude of about 20, 000 per acre, a high percentage of mortality might be tolerated, since this would leave a fully-stocked stand of young seedlings. If a sufficient number of seedlings is not established on an area, foliage spraying could reduce the number to an under-stocked level. THE EFFECTS OF 2, 4, 5-T ON TWO-YEAR-OLD SHORTLEAF PINE SEEDLINGS IN THE OUACHITA MOUNTAINS OF ARKANSAS BY EDWIN RICHARD LAWSON A THESIS Submitted to the College of Agriculture of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Forestry 1960 ii ACKNOWLEDGMENTS The writer is grateful to Dr. Robert K. Hudson for his advice and unfailing assistance in the preparation of the manuscript. Special gratitude is due to Mr. Philip A. Breigleb, Director of the Southern Forest Experiment Station, for his per- mission to use this study as a thesis problem. Special acknowledgment is also due to Dr. James L. Smith for his guidance in pursuit of the field study, collection of the final data, and forwarding of the data to the writer. Lastly, the writer is indebted to his wife, Catherine, who has shared generously in the preparation of the manuscript. TABLE OF|CONTENTS CHAPTER I. INTRODUCTION ................................ The Problem ............................. Objectives of the Study ...................... II. REVIEW OF THE LITERATURE .................. History and Extent of the Hardwood Problem . . Development of Chemicals for Controlling Hardwoods ............................... Development in Methods of Applying Silvicides. Factors Affecting the Method of Application of Silvicides ............................... The Effectiveness of Silvicides in Controlling Undesirable Species ...................... Effects of Silvicides on Coniferous Species . . . . III. DESCRIPTION OF THE STUDY AREA ............. Location .................................. Soils and Topography ....................... Climate ................................... Stand Composition .......................... IV. STUDY METHODS AND PROCEDURES ............. Treatments ................................ Study Layout and Monumentation ............. iii 12 l3 l7 19 25 25 25 26 28 31 31 33 iv CHAPTER PAGE Seedling Inventories ....................... 38 v. RESULTS OF THE STUDY ........................ ' 41! Analysis of the Data ........................ 41 Results ................................... 42 VI. SUMMARY AND CONCLUSIONS ................... 46 Objectives of the Study ..................... 46 Study Methods ............................. 46 Conclusions .............................. 47 Need for Further Research .................. 49 LITERATURE CITED ....................................... 51 APPENDIX ................................................ 59 LIST OF TABLES TABLE PAGE 1. Seedling Inventories by Treatments and Blocks ..... 41 2. Mortality of Pine Seedlings in Percent ............. 42 3. Arc Sine Transformations ........................ 43 4. Summary of the Analysis of Variance .............. 43 5. Daily Precipitation Record for 1958 ............... 6O 6. Daily Precipitation Record for 1959 ............... 61 7. Relative Susceptibility of Various Species to 2, 4-D and 2, 4, 5-T ................................. 62 8. Several Hormone-Type Phytocides ................. 65 9. A Summary of Seedling Inventories ....... . ........ 67 FIGURE vi LIST OF FIGURES PAGE Study Area before Spray Application ................ 29 General Abundance of Two-Year-Old Shortleaf Pine Seedlings ...................................... 30 The Boom-Type Spray Unit Used in This Study, and a Hurricane lvfist Blower Developed by S. A. Potts . 34 The Boom-Type Spray Unit in Operation ............ 35 Understory Hardwoods Several Weeks after Spray Application .................................... 36 One-Tenth-Milacre Frame Used for Establishment of Subplots and Subsequent Seedling Inventories ..... 37 A Schematic Diagram of Study Layout by Blocks and Plots. Letters Designate Treatments ............ 39 A Schematic Diagram Illustrating a Typical Treat- ment Plot with Subplots (D) and Spray Swaths ..... 40 CHAPTER I INTRODUCTION In the Ouachita Mountain Province of Arkansas, large areas once occupied by valuable shortleaf pine (Pinus echinata Mill. ) and loblolly pine (Pinus taeda L. ) have been gradually reduced through encroachment of undesirable hardwood species. The establishment of pine in desirable quantities is made difficult because of the in- frequent good seed years of shortleaf pine, the principal coniferous species. However, when good seed years are followed by adequate, well distributed rainfall, the forest floor will be covered with young pine seedlings. These new seedlings often cannot successfully compete with the more tolerant hardwoods under which they are established. If release is not given to these young seedlings soon after germination, most of them will die. Several years may elapse before a large quantity of seedlings is again available. During the periods between good seed years, hardwoods increase in number and size. If these undesirable hardwoods can be controlled when an abundance of pine seedlings is available, without seriously damaging the seedlings, a substantial gain will have been made toward replacing the low-value hardwoods by the pine types that formerly prevailed on these sites . Scientific names of tree species, except Pinus x sondereggerii H. H. Chapman, included in the context of this thesis correspond to those given in the Check List of Native and Naturalized Trees of the United States. U. S. D. A. , For. Ser. , Agri. Handbook No. 41. 1953, 472 pp. The Problem. One of the more popular methods of controlling undesirable hardwood species in coniferous stands is the application of Silvicides as foliage sprays. The success of spray application, from both ground and aerial equipment, has been very encouraging. Compared to other methods of controlling undesirable species, such as stem injection, frilling, and girdling, spraying is somewhat cheaper. Prevailing practices restrict the application of Silvicides to the spring and early summer seasons, since past work indicates that better control of hardwoods can be obtained in these periods (Chaiken, 1951; Burns, 1959). These are also the periods when coni- fers are the most succulent and most easily damaged (Arend, 1955). One of the most important reasons for timber stand improve- ment by the removal of undesirable hardwoods from coniferous mixtures is to increase the survival and subsequent growth of pine seedlings. Thus, the effect of silvicidal sprays on pine seedlings on an area can be the deciding factor in determining whether to use a foliage spray or single-stem treatment for controlling hardwoods. The effects of Silvicides applied as foliage sprays upon two—year-old shortleaf pine seedlings has never been determined in the Ouachita Mountain Province. Forest land managers in this area, who desire to spray in seasons just after the occurrence of good seed years followed with adequate moisture, face the dilemma of needing to treat large areas for hardwood control that are largely covered with pine seedlings that might be killed by Silvicidal spraying. Such a kill can not be tolerated in an area where good seed years occur as infrequently as they do in this region. Thus, the problem of deciding if and when to spray for controlling undesirable hardwoods becomes extremely important. The Objectives of the Study. The investigation here reported was designed to test the effects of foliage spraying for control of un- desirable hardwoods upon shortleaf pine seedlings in the Ouachita Mountain area of west-central Arkansas. Effects of spray application upon these seedlings was measured in the early summer, and in the late growing season. One concentration of 2, 4, 5-T was utilized. The study was replicated in place, but not in time. CHAPTER II REVIEW OF THE LITERATURE History and Extent of the Hardwood Problem. Controlling undesirable species is a problem in all forest regions of the United States, and is of particular importance in the eastern half of the country. According to the Timber Resources for America's Future (U. S. D. A. , 1958a), 74 percent of the hardwoods of the eastern United States are of low grade or cull quality. This large percentage of such hardwoods is partly the result of man's past cutting practices. A statement from the Annual Report of the Southeastern Forest Experiment Station (U. S. D. A. , 1958b) summarizes man‘s major part in the existence of such a large amount of undesirable hardwoods: In bygone days lumber prices were so low and utilization practices so primitive that markets could be found only for the best quality yellow-popular, pine, and white oak. As prices rose and utilization improved, successive waves of loggers returned to high grade the forests. But always poorly formed or defective trees and those of inferior species were left behind. Thus, by default millions of acres of once-productive forest land have been rendered to inferior hardwoods. Returning these lands to productivity is one of the major objectives of forest managers in the South today. In general, this situation has its counterpart in other U. S. forest regions. In the Lake States, the white pine type has been reduced by about a million acres and replaced by the aspen-birch type. The problem is similar in the Northeast, where hardwoods tend to replace the spruce- fir and white pine types, after cutting. Past cutting practices are not the only reason for replace- ment of good species by undesirable Species. Hardwoods make up the climax type in much of the eastern United States, particularly in the South (Walker, 1956). Man has often accelerated the succession toward this climax type. Present silvicultural practices in many areas of the eastern United States tend to speed up the natural succession. Coile (1949) indicates that release of understory hardwoods while harvesting pine crops, even under a good management plan, often allows the hardwoods to develop and replace the more desirable pine. Ordinarily, southern pine stands approaching maturity are characterized by a low, dense understory of undesirable hardwoods. When such pine stands are harvested under any of the conventional silvicultural methods, subsequent pine reproduction often is unable to compete successfully with the existing hardwood understory. Coile (1949) further states that: After cutting, such areas revert from pine, which is of relatively high value and rapid growing, to a mixture of hardwoods of poor quality, slow growth and low value. The work of Brender and Nelson (1954) supports Coile's conclusions. These authors found that the hardwood canopy area doubled 2 years after the clear cutting of a 90 year-old Shortleaf pine stand, despite severe damage to hardwoods during the logging operation. Stands such as this will be very difficult to regenerate to pine unless measures are taken to eliminate or reduce the undesirable hardwoods. The high-grading of forest stands in the past and the encroachment of hardwoods upon coniferous sites, has created a problem throughout much of the eastern United States. Reynolds (1947), Campbell and Peevy (1950), Demmon (1951), Mann (1951), Reynolds (1951), Cassady and Mann (1954), Ferguson and Stephenson (1955), Goodrum and Reid (1956), Sluder (1958), Burns (1959), and others working in the South have recognized that there are vast areas needing hardwood control. Carlson (1950) estimates there are more than 100 million acres of formerly valuable southern forest types that are being replaced by undesirable trees. He further estimates that these undesirable hardwoods represent an annual loss of $2 to $3 per acre, or about $200, 000, 000 to $300, 000, 000 annually to southern forest industries. Roe (1957) estimated that there are 7, 650, 000 acres in need of regener- ation in the Lakes States and most of this area is occupied by undesirable species. Clark and Liming (1953) have recognized that there are millions of acres in the Central States Region with considerable amounts of undesirable hardwoods present. Gratkowski (1959) estimates that there are more than a million acres of commercial forest land in southwestern Oregon that have been reduced to dense stands of brush. Schubert (1955) has pointed out that there are l, 700, 000 acres of commercial forest land occupied by undesirable species in the western Sierra Nevada of California. The encroachment of undesirable species into sites formerly supporting more valuable types usually affects timber management in one of three ways. First, these undesirable species increase the difficulty in regeneration of the more valuable species (Furnival, 1954). Coniferous seedlings generally can regenerate under an over- story of hardwoods only with great difficulty. Seedlings that are not released soon after they originate usually die. Second, hardwoods generally reduce the growth of the more desirable species which have been already established. Smith (1958) found that complete elimination of the hardwood understory of a 60 year-old shortleaf pine stand increased the rate of growth of the old pine by more than 20 percent. Zahner (1958) found that water losses during midsummer were about 25 per- cent more rapid in plots with a hardwood understory than in plots with hardwoods chemically eradicated. He further found that when soil moisture was high, the evapo-transpiration from the treatment areas was nearly equal. However, as summer advanced and the soil dried, moisture levels in the plots without a hardwood understory were more than 50 percent greater than in those plots in which the hardwood understory was retained. Harrington (1958) found that shortleaf pine seedlings released from low-grade hardwoods grew twice as fast the first season as did unreleased seedlings. Those seedlings that were released grew an average of 8. 3 inches in height in contrast to 3. 4 inches height growth for the unreleased seedlings. Furnival (1954) also indicates that cull hardwood species are aggressive in reproducing themselves in pine stands. A third undesirable affect of hardwoods on coniferous sites is that they make routine forest management practices more difficult. Movement of managemental personnel through the stand is hindered, and visibility of individual stems or the stand as a whole is reduced resulting in loss of time and poor-quality marking. With an idea of the extent of the problem of inferior hard- woods, and of the difficulties it presents in forest management, one can readily see that control of inferior species can be of practical and economic importanc e . Development of Chemicals for Controlling Hardwoods. With the increased demand for certain forest products, particularly products from conifers, forest land managers became increasingly interested in developing methods of controlling undesirable hardwoods to increase production of more desirable Species. The greatest progress in developing methods of controlling undesirable hardwoods has been made by the use of chemicals. From the late 1920’s to World War II, woody plant eradication was done mechanically or by application of sodium arsenite, or other such chemicals, to various cuts through the bark of the un- desirable trees. Sodium arsenite is essentially non-selective and is extremely toxic to animal life (Rudolf and Watt, 1956). lkenberry (1938) indicates that sodium chlorate, 27O diesel oil, ammonium thiocyanate, or various arsenicals were used in this early period, with a varying degree of effectiveness. Chaiken (1951) reports that sodium chlorate, calcium chlorate, potassium chromate, iron sulfate, copper sulfate, zinc chloride, sodium chloride, ethylene oxide, kerosene, creosote, and many other substances were used in this early period, but none of them was entirely satisfactory. Ideally, a chemical silvicide should be highly effective in killing undesirable species, available in large quantities at reasonable costs, easy to handle and apply, non-toxic to higher animals, and non- corrosive to equipment. Early chemicals usually failed to meet one or more of the requirements of the ideal silvicide. After World War 11, new chemicals were developed that were effective as silvicides and not toxic to humans or domestic animals. The more important of these are Ammate (ammonium sulfamate), and various derivatives of the phenoxyacetic acids and closely related compounds. Ammate was developed prior to the silvicides derived from the phenoxyacetic acids, and rapidly gained wide use in forestry. Ammate is supplied in the crystalline form, and is highly soluble in water. It is also highly corrosive to most metals, making it undesirable to apply as a spray or liquid mixture. Ammate is essentially a non-selective silvicide, although it has been reported by Nichols (1952) that some differences in response of species occur. This silvicide has been applied in various cuts or incisions through the bark and as a foliage 10 spray, although, the latter may not be very practical. Hough (1950) found that 100 to 400 pounds of ammate crystals per acre were required when the silvicide was applied as a foliage spray, making it very costly to use as such. Closely following the development of Mmate, new growth- regulating chemicals became available. Rudolf and Watt (1956) indicate that various derivatives of 2, 4-D (2, 4-Dichlorophenoxyacetic acid) and 2, 4, 5-T (2, 4, 5-Trichlorophenoxyacetic acid) are the substances commonly used for woody plant control in the Lake States. Sluder (1958) reports that 2, 4-D and 2, 4, 5-T are being used in place of older chemicals for control of undesirable Species in the South. Like Arnmate, 2, 4—D and 2, 4, 5-T are translocated as they enter the assimilate stream of plants. High temperatures and low humidities favor translocation in woody plants (Rudolf, 1951). Crafts (1953) found that hormone sprays such as these enter plant leaves through the cuticle and pass in to the living cells, or that they enter the plant through the roots. He also found that one of the unique features of these chemicals is their ready absorption and translocation through vascular tissues, and that the tissue involved in absorption and translocation of hormone-type sprays are mostly mature. The cells that accumulate these compounds, however, are mostly meristimatic, responding by increased water uptake, abnormal division and growth, high respiration, and therefore death. The phenoxyacetic acid compounds are available as metallic 11 salts, amine salts, and in ester forms (Chiaken, 1951b). The ester forms that have a low volatility have been found to be most effective for woody plant control (Rudolf and Watt, 1956). Phenoxyacetic acid compounds are somewhat selective in their effects on vegetation. 2, 4-D is effective in killing alder, sumac, willows, elder, and black locust, but rather ineffective on oaks, hickories, maples and most conifers (Rudolf and Watt, 1956). 2, 4, 5-T, on the other hand, is effective on the oaks, ashes and hickories as well as the plants susceptible to the 2, 4—D. Table 7 in the Appendix contains a list of relatively susceptible and non-susceptible species. Different species in the two groups mentioned above react to the silvicides in various degrees. Sometimes the 2, 4-D and'2, 4, 5-T are mixed in equal proportions to form "brushkillers, " which are effective on more species than is the 2, 4-D alone, but may not be as effective as the 2, 4, 5-T alone. The latter chemical is somewhat more expensive than the 2, 4-D and the brushkiller. The effectiveness of commercial silvicides in killing woody species varies somewhat with different formulations used. Commercial products contain wetting agents, stickers, emulsifiers, penetrants, and other inert agents (Walker, 1956). These agents may increase the effectiveness of the chemical in killing plants by increasing the penetration and subsequent movement of the chemical within the plant (Sutton, 1958). A list of some of the hormone chemicals and the 12 manufacturers of each are given in Table 8 of the Appendix. Developments in Methods of Applying Silvicides. Rapid progress in the development of equipment for applying silvicides followed soon after the new chemicals became available. In the be- ginning the new silvicides were applied to axe cuts made in woody plants. Devices soon were designed that could be used to make the incision and apply the silvicide in a single operation. The Cornell Tool and the Little Tree Injector are examples of these. Silvicides were also used to supplement various mechanical methods of controlling undesirable species. Axe girdling and frilling, and machine girdling (most common type of girdler is the Little Beaver Tree Girdler) are mechanical methods of controlling undesirable hardwoods. (These were often made more effective by spraying or pouring silvicidal mixtures on the freshly exposed surfaces. In recent years, great progress has been made in the use of power equipment for foliage application of silvicides. Although hand Sprayers are often used when small areas are to be treated, foresters everywhere are interested in methods of rapidly applying Silvicides to large areas. Spray units have been mounted on jeeps, trucks, and tractors for ground application of silvicides. The first power spray units used in forestry generally required large volumes of diluent, usually 30 to 100 gallons of mixture per acre, in order to obtain good coverage and high mortality of the undesirable species. Day (1948) 13 indicates that it usually takes from 100 to 300 gallons of spray mixture per acre to wet the leaves and stems thoroughly in foliage spraying. Newer equipment, generally called ”concentrated spray equipment, " allows application of lethal doses of silvicides with only 2 to 5 gallons of mixture per acre. The hurricane mist blowers are ground equipment of this type. Concentrated spray equipment has also been adapted to aircraft for application of silvicides. The use of air- craft offers the possibility of covering large areas very rapidly, although aircraft have some undesirable features that will be discussed in the next subtopic of this report. The greatest progress in the use of hormone sprays has been in the elimination of undesirable herbaceous vegetation. Hormone sprays were widely used on various agricultural crops before they were tried in forestry. Considerable progress was also made in the development of equipment for application of these sprays. Potts (1958) estimates that only 2 percent of the research on hormone sprays has been devoted to forestry applications. He is of the opinion that ”this is potentially a very valuable, almost untouched field for development. " Factors Affectig the Method of Application of Silvicides. Obviously, cost is an important factor affecting the method to be used for application of silvicides. Small areas, generally 40 acres or less, cannot yet be economically sprayed with aerial equipment. Very small areas cannot be economically sprayed with ground power equipment. 14 For such areas, hand spraying of foliage may be suitable. Some mechanical method, such as girdling or frilling, may be equally suitable. The costs of controlling undesirable hardwoods by the technique of girdling and spraying is also dependent upon the number of stems per acre and the species of the hardwoods to be eliminated. Equally effective kill of trees above 10 inches in diameter can be accomplished by girdling without spraying. Costs of control will increase in direct proportion to percentage of species more resistant to the silvicide encountered in the stands. Costs of chemical eradication may also vary considerably, depending on the method used, size of area treated, number of stems treated per acre, efficiency of the operation, and the like. Little and Mohr (1956) indicate that it cost $13 to $15 per acre for frilling and chemically treating 385 trees averaging 6 inches in diameter. Chemical treating was done with a 1 percent solution of 2, 4, 5-T in diesel oil. Huckenpahler (1954) found that it cost about $3. 60 per acre to frill trees greater than 3 1/2 inches in diameter at breast height, and if Ammate was used, the cost was increased to $8. 38 per acre. American Chemical Products Inc. (1959) estimates that costs range from $6. 50 to $8. 00 per acre to apply a mixture of 2 pounds of acid, 1/2 gallon of oil and 4 gallons of water with a mist blower. Hawkes (1953) aerially sprayed l, 000 acres in Oregon at a total cost of $5. 15 per acre, using 2 pounds of acid in 8 gallons of water. Walker 15 (1956) stated that 1 1/2 pounds of 2, 4, 5-T mixed with diesel oil will cost about $8. 00 when aerially applied. His estimate was based on application at a rate of 2 1/2 gallons of mixture per acre. Aerial spray equipment is usually unsuitable for Spraying forest stands with an upper canopy of coniferous Species and an under- story of undesirable hardwoods species. The spray droplets are inter- cepted by the coniferous canopy and thus fail to cover adequately the understory vegetation (McConkey, 1958). Ground spray equipment would likely be more effective in dispersing the silvicide on the undesirable vegetation in this Situation. Aerial spraying is also very hazardous to use in areas where the terrain is extremely rough. Flying under these conditions is likely to result in death of personnel and loss of equipment. Ground spray equipment is likewise dangerous to use on rough terrain, where the equipment is likely to overturn and injure'the driver. Another disadvantage of the use of ground equipment on steep topography is that constant ground speeds are difficult to maintain. The vehicle will tend to speed up when going downhill and slow down when going uphill, resulting in unequal distribution of the spray materials. Use of aerial equipment is often limited by local weather conditions. Visibility must be good and wind velocity must be low, usually five miles per hour or less. In many areas, weather conditions limit the use of aerial equip- ment to a few hours in the early morning and late evening. Suitable landing areas for refueling, and for refilling the spray tanks, must be 16 within a reasonable distance from the area that is to be sprayed. Obviously, aerial spraying, or any other type of foliage spraying, is limited to the growing season. During dormant seasons, individual stem treatments must be used. Aerial spraying is usually limited to large areas because of possible drift of the silvicide to nearby susceptible crops, and because of economic factors involved. Gantz (1959) points out that drift may be reduced by using invert emulsions or pellet forms of 2, 4-D and 2, 4, 5-T. Allowing spray to drift onto other tracts outside the boundaries of the tract being sprayed is poor policy. Not only can this drifting damage the vegetation on others‘ property, but it creates poor public relations and may set back the progress of aerial spraying or even cause it to be prohibited by law (Arend, 1959). Aerial application might also be unsuitable for spraying areas having an abundance of very young coniferous seedlings, since they may possibly be damaged (Smith and Lawson, 1960). Arend (1955) points out that most conifers may be damaged during the active growth period by light applications of 2, 4-D and 2, 4, 5-T foliage sprays. However, he found that no apparent damage occurs after the active growth period has declined and new growth has hardened off. Once equipment or containers have been used for application of hormone-type silvicides, they should not be used for application of other agents, such as insecticides. Residues of the hormone chemicals 1Invert emulsions are chemicals in which water droplets are dispersed through a continuous system of oil, giving an invert or water- in-oil emulsion in contrast to a conventional emulsion which is oil-in-water. 17 are extremely difficult to remove from equipment or containers, and if such containers are used for other treatments, very valuable species that are very susceptible may be damaged or killed (Leonard, 1956; Day, 1956). The Effectiveness of Silvicides in Controlling Undesirable Species. The ability of a silvicide to kill an individual tree is largely dependent on the particular silvicide used, the concentration of the lethal component of the silvicidal chemical present,1 the type of diluent used, the thoroughness of application, the physiological condition of the plant, weather conditions, and perhaps, features inherent in the plant (Jankowski, 1955). As previously mentioned, hormone-type silvicides are translated in the assimilate stream-of the plant. Any factor which increases the amount of acid entering the assimilate stream of the plant, can generally be considered to increase the effectiveness of the silvicide. Killing is doubly insured if roots can be killed, which prevents possible sprouting. Results of many tests indicate that silvicides are effective under several methods of application, with rather narrow economic limits in amount of chemical to be used. Davis (1958) observed 93 percent mortality of mixed hard- woods, resulting from the basal application of a 23. 5 pounds 1In the phenoxyacetic acid compounds, the acid is the lethal ingredient. Acid content of the hormone sprays is usually expressed in pounds per gallon of the silvicide. The effectiveness of the acid is sometimes increased by adding agents to facilitate penetration and absorption of the acid. 18 ahg concentration of 2, 4, 5-T. Only 5 percent of these stems sub- sequently sprouted. The basal spray was a 2, 4, 5-T-diesel oil solution and was applied in December of 1953. On the contrary, Grano (1953) found that 5 percent solutions of 2, 4, 5—T, applied as basal sprays with an oil diluent, were not very effective in killing undesirable species and prohibiting sprouting. The spray was applied in May and June to oak trees smaller than 11. 5 inches diameter at breast height. Arend (1953) obtained good control of aspen, using a basal application of a 12 pounds ahg concentration of half 2, 4-D and half 2, 4, 5-T in diesel oil. Grano (1953) found that a 1 percent water emulsion of 2, 4, 5-T killed southern red oak (Quercus falcata Michx.) and prevented sprouting when applied to frills in early spring. The use of 2 percent emulsions appeared little better than the 1 percent emulsions in preventing sprouting. Results were measured 17 months after treatment. Leonard (1956) recommends the use of 2 pounds of ”brushkiller" per acre in 1 gallon of diesel oil with enough water to make a total mixture of 40 gallons. This recommendation was for application with boom-type ground equip- ment for woody plant control in California. Hedrick, _e_t__a_1. (1953) indicated that less than 10 percent of the brush on burned chamise areas survived spray treatment with 2, 4—D and 2, 4, 5-T. They also found that higher concentrations of sprays were more effective than weaker ones. Stransky (1959) obtained a much higher top—kill when girdling was supplemented by application of 2, 4, 5-T, instead of using Acid per one-hundred gallons of mixture. 19 girdling alone. Both concentrated and dilute 2, 4, 5-T were effective, resulting in 97 percent crown mortality. Stransky found also that the concentrated 2, 4, 5-T did not give good sprout control. Little and Mohr (1956) obtained 95 percent hardwood mortality, resulting from the application of a 1 percent solution of 2, 4, 5-T in number 2 fuel oil. They found that 99 percent mortality resulted when a 2 percent solution was used. This mortality was measured 31 months after treatment. McQuilkin (1957) in testing the frilling method of hardwood control, found that oil was a better carrier for the silvicides he used than was water. Smith (1959) obtained 59, 69, and 89 percent kills the first year after using 24, 36, and 44 pounds ahg concentrations of 2, 4, 5-T in diesel oil. Treatments were applied with the Little Tree Injector to white oak(Quercus alba L. ) stems varying in diameter from 3 to 6 inches. No sprouting occurred after any of these treatments. Effects of Silvicides on Coniferous Species. Previously mentioned tests involved the application of treatments to individual stems. In this respect, they are very selective since treatment can be applied to the undesirable stems without adverse affects on the desirable species. If, however, foliage spraying is used, both desirable and undesirable species receive the treatment. Hawkes (1953) was one of the earliest to publish his results in testing the aerial application of selective silvicides for release of coniferous species. He reported on the aerial application of silvicides 20 for the release of Douglas fir, Sitka spruce and Port-Orford-cedar (2-8 feet tall) growing under alder and willow (10-20 feet tall). He used one mixture of 2 pounds acid equivalent of 2, 4—D ester in 8 gallons of water per acre, and a second mixture with 1 gallon of diesel oil and 7 gallons of water per acre. Both mixtures successfully defoliated the alder and willow. Shoots of the conifers under the alder curled somewhat, but straightened by late summer. Those conifers that were fully exposed suffered greater damage. Coulter and Ralston (1954) obtained good kill of scrub white, red, and northern pin oaks that were over-topping a 15-year-old red pine plantation, without apparent injury to the pines. Coulter and Ralston tested the aerial application of 1 pound of 2, 4, 5-T acid equivalent in 1. 0 gallon of fuel oil and 3. 75 gallons of water applied at a rate of 5 gallons of mixture per acre. They also tested 2 pounds of 2, 4, 5-T acid equivalent in l. 0 gallon of fuel oil and 3. 50 gallons of water applied at the rate of 5 gallons of mixture per acre. No important variations occurred between the two concentrations tested. McConkey (1958), using 1 and 3 pounds acid equivalent of 2, 4, 5-T in oil at a rate of 2 1/2 gallons per acre, believes he permanently released young pines from the competition of birches and oaks. The 3— pound rate was most effective in releasing young white pines, but about 1/5 of these pine seedlings showed some injury. A year later, however, distorted branches exhibited new growth, and dead terminals 21 were replaced by lateral shoots. Where l-pound of 2, 4, 5-T acid was used, no damage was apparent. Treatments were applied on July 15, 1954. Arend (1955) tested the tolerance of conifers to foliage application of l and 2 pounds of 2, 4, 5-T acid per acre in a water- oil emulsion. He found that light application of these two concentrations will damage the new growth of most conifers. Arend found also that if spray application is made in late summer, after the growth has hardened off, the silvicides have no apparent effect on the conifers. Burns fl. (1959) tested the effectiveness of several formulations of 2, 4, 5-T in releasing shortleaf and loblolly pines from hardwood competition. The formulations of 2, 4, 5-T were applied at a rate of 2 pounds acid equivalent per acre in water, and also in oil- water emulsions. Some pine needles turned brown within a few weeks after spraying. With the exception of some seedlings, the damaged pines had begun to recover before the growing season was over. As a whole, Burns and his associates found that pine mortality was negligible. Hardwoods reacted inconsistently to the treatments. Some formulations resulted in heavy mortality of some species and low mortality in others. Harrington (1959) tested water and diesel oil as carriers for a 60-pound ahg concentration of 2, 4, 5-T. The mixtures were sprayed from a helicopter at the rate of 3 gallons of mixture per acre, which corresponds to 1. 8 pounds acid equivalent of 2, 4, 5-T per acre. 22 Total hardwood crown coverage was reduced by 67 percent when diesel oil was used as a carrier for the silvicide. A 42 percent reduction of crown coverage resulted when water was used as a carrier. Reduction of hardwood crowns was measured 2 years after spraying. Rogers (1958) obtained 90 percent defoliation of hardwoods in one growing season after aerial application of 2 pounds of 2, 4, 5-T acid per acre with diesel oil as a carrier. Application was at the rate of 5 gallons of mixture per acre. Two years after the spray application, 50 percent of the defoliated trees had died and many of the remaining ones were of low vigor and were not expected to live. Although no pine trees were killed, some lost as much as 75 percent of their needles. These, however, developed new needles during the same growing season. 4 Darrow (1956) found that only minor and temporary injury to loblolly and shortleaf pine and no injury to longleaf pine (Pings palustris lviill.) occurred after aerial spraying for hardwood control in Texas. Darrow's tests were made with 2 1/2 pounds acid equivalent of 2, 4, 5-T per acre in an oil—water emulsion. Ray (1958) found that low volatile esters and amines of 2, 4, 5-T were effective in reducing hardwood brush in northern Arkansas. He found that 2 pounds acid equivalent per acre were effective, economical and generally did not cause serious injury to pine. He found also that higher concentrations of 2, 4, 5-T acid in diesel did cause contortion 23 of needles and shoots. Silker and Darrow (1956) found that overstory pines and advanced pine reproduction varied in reaction to an aerial spray treatment, depending upon species and crown class. Their tests with 2, 4, 5-T and Silvex (propionic acid) resulted in "burning" two- and three-year-old needles of longleaf and Sonderegger pine (Pinus x sondereggerii H. H. Chapman). This application did not damage the buds and terminal shoots. Loblolly and shortleaf pines were similarly affected, but to a lesser degree. When shortleaf and loblolly pines were fully exposed to the spray, the terminal shoots were often killed back. These pines overtopped by hardwoods were not affected. Smith and Lawson (1960) tested foliage spraying with a mixture consisting of 1 gallon of 2, 4, 5—T (4 pounds acid equivalent per gallon), 1 gallon of diesel oil, and 38 gallons of water. Spray application was made with a boom-type spray unit mounted on. a tractor at a rate of 40 gallons of mixture per acre. Spray application in June resulted in 90 percent mortality of first-year shortleaf pine seedlings. This mortality is in contrast to the untreated control plots which had 32 percent mortality. When the same spray treatment was applied in August, 71 percent mortality resulted. The corresponding natural mortality from the control plots in this instance was 33 percent. The results of the above-mentioned studies indicate that newer silvicides and techniques of application are effective in controlling 24 undesirable hardwoods, generally without serious damage to coniferous species. The effectiveness of silvicides in controlling undesirable species is largely dependent on the amount and type of (silvicide. used, type and amount of diluent used, rate of application, method of application, season of application, number of stems, size of stems, age of stems, vigor of stems, and site factors. Damage to coniferous species also is largely dependent on these factors. 25 CHAPTER 111 DESCRIPTION OF THE STUDY AREA Location. The area selected for installation of this study is located in the Ouachita Mountain Province of west-central Arkansas, about 7 miles north of the city of Hot Springs. The study area is near the center of section 9, township 2 south, range 19 west, in Garland County. Soils and Topography. Much of the western and northern parts of Arkansas are hilly and mountainous. The southern and eastern parts are mostly lowlands. The Ouachita Mountains make up a large portion of the mountainous section. The Ouachita Mountain area is largely composed of narrow east-west ridges separated by rather narrow valleys. Some of these ridges reach elevations of 2, 500 feet or more. The soils over much of the highlands or mountainous areas have been moderately eroded and have lost much of their fertility (U. S. Department of Commerce, 1959b). Erosion in the region may be particularly severe if the land has been denuded of its vegetative cover. This erosion is evident where roads have been improperly drained or improperly constructed. Soils of the Ouachita Mountains are often characterized by the presence of large amounts of rounded or angular quartz, generally 26 ranging from 0. 25 to 3. 0 inches in diameter (Smith and Lawson, 1959). As much as one—third of the soil volume may consist of rounded or angular quartz gravel. The finer soil separates (less than 2 mm. in diameter) of the surface soil are largely silt and clay. The clay content of these soils often increases with increased depth. Clay particles may make up nearly half of the soil volume in the lower portions of the solum. The moderately high clay content gives the soils a some- what plastic nature (Smith and Lawson, 1959). Most of the soils in the Ouachita Mountain region belong to the red and yellow podzolic Great Soil Group. Soils of this group are characteristically formed in much of the warm—temperate climate of southern and southeastern United States (Lutz and Chandler, 1946). These soils are typically shallow on the steep slopes and deeper in the valleys. Climate. Climatic differences between the highlands and lowlands of Arkansas are not so great as the local differences between the mountain ridges and mountain valleys. Generally, the climate of western and northern Arkansas is somewhat cooler, with greater temperature extremes, lower humidities, and has less cloudy weather. Maximum and minimum temperatures do not vary considerably over the state. Maximum temperatures may exceed 1000 F. during the summer months. The winters are generally of o . Short duration, with a temperature of 0 F. occasionally occurring 27 during January and February. The long term average temperature for the station nearest the study area is 64. 10 F. The absolute temperature range for Arkansas is from 1200 F. (recorded at Ozark on August 10, 1936) to a -290 F. (recorded at Pond on February 13, 1905). Rainfall in the state is normally abundant and fairly well distributed, although short periods of dry weather do occur in some areas. Tables 5 and 6 of the Appendix are daily precipitation records for 1958 and 1959 respectively. These tables Show a nearly normal distribution and total precipitation. The average number of days with measureable precipitation ranges from 100 in the west to 112 in the east. The normal precipitation for the state ranges from 40 inches to 55 inches, with the highest averages occurring in the Ozark and Ouachita Mountain areas. The average for the Hot Springs Station from 1931 to 1955 is 55. 03 inches. Local orographic influences tend to affect the precipitation more than does the geographic location in the state. The precipitation is generally of localized—type, except during short periods in the fall, winter, and spring, when cyclonic storms prevail. Northwest Arkansas receives about 60 percent of its annual precipitation during the months of April through September. The southern part receives less than half of its annual precipitation during this period (U. S. Department of Commerce, 1959b). A long growing season is characteristic of Arkansas, ranging from 180 days in the northwest to 230 days in the southeast. 28 The mean date of the first fall freeze for the Hot Springs Station is November 10, and the mean data of the last spring freeze is March 29 (U. S. Department of Commerce, 1959b). Stand Composition. The upper canopy of the stand utilized for this study was primarily shortleaf pine, with an occasional dominant hardwood. The pine was approximately 60 years of age. The under- story consisted primarily of a dense mixture of white oak (Quercus alba L. ), black oak (Quercus velutina Lam. ), blackjack oak (Quercus marilandica Muenchh. ), post oak (Quercus stellata Wang. ), hickory (Carya spp. ), and black gum (stsa silvatica Marsh. ). A few other tree Species, shrub species, and herbaceous species occurred less frequently. Most of the hardwoods were less than 20 feet in height, many of which were less than 12 feet. Occasional hardwood stems were somewhat larger. The typical understory vegetation occurring on the study area is illustrated in Figure 1. An abundance of two-year-old shortleaf pine seedlings, ranging in height from about 4 to 6 inches at the time of Spray application, existed beneath the hardwood understory, resulting from the excellent pine seed crop of 1957 and favorable climatic conditions in the sub- sequent growing season. An adequate and well-distributed rainfall is of primary importance in determining the survival of seedlings after germination. Tables 5 and 6 show the amount and distribution of rainfall in 1958 and 1959, following the excellent pine seed crop of 1957. Figure 2 illustrates the abundance of seedlings occurring over much of the area. Figure 1 Plot 3 of Block 2 before Spray Application. Note the Two-Storied Stand; Overstory of Pine and Understory of Hardwoods. August, 1959 29 Figure 2 View of Forest Floor, Illustrating Typical Abundance of Two-Year—Old Shortleaf Pine Seedlings before Treatment. August, 1959 30 31 CHAPTER IV STUDY METHODS AND PROCEDURES This study was designed to determine the effects of foliage spraying in Arkansas for hardwood control, with 2, 4, 5-T upon two-year old shortleaf pine seedlings, when applied in the early (June) and in the late (August) growing season. Spray applications were made in the early and late growing seasons of the summer of 1959 only. Treatments. The study utilized four treatments, two of which were spray applications and two of which were controls, randomized among four plots in each of three blocks. Procedure was as follows: A. One plot in each block was sprayed in early June when the average soil moisture in the top 24 inches at or near field capacity, or at between 1/3 and 3 atmospheres of tension. Relative humidity was above 85 percent at the time of spray application. B. One control plot in each block was utilized as a check for determination of natural mortality occurring from early June to December. C. One plot in each block was sprayed in early August when the average soil moisture and relative humidity conditions were essentially the same as for Treatment A. D. One control plot in each block was utilized as a check for determination of natural mortality occurring from early August to December. The chemical used in all spray applications consisted of an emulsion of a low-volatility 2, 4, 5-T ester in diesel oil and water. The 32 2, 4, 5-T was a commercial product designated as Dow Esteron 245 OS. Dow Esteron 245 OS contains 4 pounds of 2, 4, 5-T acid equivalent per gallon. The chemical may be designated also as 2,4, 5-Trichloro- phenoxyacetic acid, which is a propylene glycol (C3HéO to C9H18O3) butyl ether ester. One gallon of Dow Esteron 245 OS weighs 6. 15 pounds and contains 65 percent of the ester. The application in all spray treatments was at the rate of 40 gallons of mixture per acre, the mixture consisting of 1 gallon of diesel oil, 1/2 gallon of ester, and 38 gallons of water. Spraying was carried out by means of a tractor-mounted boom-type spray unit, operating at a pressure level of 22 pounds per square inch. The spray unit is illustrated at the right Side of Figure 3. Figure 4 shows the spray unit in operation. Figure 5 shows plot 3 of block 3 several weeks after spray application. The unit was designed to spray a strip 22 to 26 feet wide. Spray coverage was obtained by starting the spray operation 11 feet from one edge of each plot and continuing in a back-and-forth fashion at 22 foot intervals throughout the plot. This technique is illustrated in Figure 8. A man guided the tractor along the center of the strip by walking at a safe distance in front of the tractor 22 feet from the center of the previously sprayed strip. Spray strips were oriented parallel to the longest sides of the plots. Each plot was 2 by 2 1/2 chains and constituted an area of 1/2 acre. 33. Study Layout and Monumentation. Three blocks, each consisting of four plots, were established. Each of the four treatments including controls, was randomly assigned to one plot in each block. Each of the twelve plots was one-half acrein size and rectangular in shape. A schematic representation of the layout of blocks, plots, and subplots is shown in Figures 7 and 8. Each corner of each of the plots was monumented by painting a blue band 4 inches wide around the tree nearest the plot corner. Plot boundaries were marked by painting blue patches on trees at eye level at frequent intervals along plot boundaries. The sampling method consisted of complete pine seedling inventories in ten one—tenth milacre subplots within each one—half acre plot (Figure 6). The ten subplots were located tentatively at intervals of two-tenths chain along a diagonal line from a point one—half chain from the beginning corner. This corner was chosen mechanically at the time of plot establishment. If 5 seedlings were not present within the boundaries of any proposed subplot, the nearest equivalent area to this proposed plot, which contained 5 seedlings or more, was estab- lished as the subplot. Figure 3 Boom-Type Spray Unit (Right) Used in This Study. Hurricane Mist Blower (Left) Developed by S. A. Potts. August, 1959. 34 Figure 4 Boom-Type Spray Unit in Operation. Silvicidal Mixture Is Dispersed as Finely Divided Droplets. August, 1959 35 Figure 5 Understory Hardwoods in 60-Year- Old Shortleaf Pine Stand Several Weeks after Silvicidal Spray Application. Leaves Persisting on Oak Trees Are Dead. September, 1959 36 Figure 6 One-Tenth Milacre Frame Used for Establishment of Subplots and for Sub- sequent Seedling Inventories. Note Wooden Stake and Wire Pin Used for Monumentation. August, 19 59 . 37 Each 1/ 10 milacre subplot was laid out on the ground with the square frame provided (Figure 6). Each subplot was 2. 08 feet square. Monumentation of each of the subplots was accomplished by staking 2 diagonal corners (Figure 6). One corner was marked with an 18-inch wooden stake having the top three inches of one side painted blue, the other corner was marked with a wire pin. Each wooden stake within each subplot was assigned an identifying letter taken from the group A to J. This letter was placed upon the stake with a wax pencil. Seedling Inventories. Seedling counts for determination of mortality were made on the subplots immediately following the spraying of each plot. Those plots (B) designated as control plots for the early-season spray treatment (Treatment A), were inventoried at the time of the spraying. Those plots (D) designated as control plots for the late-season spray treatment (Treatment C) were inven- toried at the time of the late spraying. The initial inventory for the early-season spray and control plots was made on June 11, 1959. The initial inventory for the late- season spray and corresponding control plots was made on August 5, 1959. The final inventory for all plots was completed in December, 1959. 38 BLOCK I . 39 C B 4 chains A D R 5 chains ————->-( BLOCK II A D B C BLOCK III B C A D Figure 7 A Schematic Diagram of Study Layout by Blocks and Plots. Letters Designate Treatments. 40 Tr .5 V” I . ---- --Nv ............................................ O O m .................................................... .m o o , 4. IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII O O 0 LP .................................................... #22»! Figure 8 A Schematic Diagram Illustrating a Typical Treatment Plot with Subplots (El) and Spray Swaths (Dashed Lines). l 41 C HAPTER V RESULTS OF THE STUDY Analysis of the Data. A summary of the seedling inventories made on the subplots by treatments and blocks, is presented in Table l. The data in this summary represent the total number of seedlings in the 10 subplots in each treatment plot, at the time indicated. The data from all inventories are presented in Table 9 of the Appendix. These data are categorized by subplots, treatment plots, and blocks. TABLE 1 SEEDLING INVENTORIES BY TREATMENTS AND BLOCKS Blocks I II III 4..) 5 > >. > > > >. >. :>~ >~ 5" 1'4 f" H TH f" 3.; H .H E o o .51 o o .21- o o :1 “ r—l +4 +3 «3 .-1 4.: 4.» m H +3 +4 «5 “3 f3 53 '3 5 t .9: 5 '8 5 i: .52 5 ’8 5 i: fixi> 53> o .*:’.> 33> o .t’.> ,§> o [-1 E. .5 Ln .5 2 .5. .5 In E. E E. .S In E 2 A 150 42 108 152 41 111 157 17 140 B 142 107 35 150 109 41 143 100 43 c 166 85 81 160 1’65 95 159 14 145 D 156 148 8 157 146 11 165 141 24 early season spray. early season control. late season spray. late season control. Treatment A Treatment B Treatment C Treatment D 42 The analysis of variance for this investigation was based on the percent of seedlings that died out of the original number that occurred in the subplots of each plot. The percent mortality in each plot was determined by dividing the total mortality by the number of seedlings present in the initial inventory. These percentages are summarized in the following table: TABLE 2 MORTALITY OF PINE SEEDLINGS IN PERCENT Treatments ~ Blocks 1 2 3 A. Early-Season Spray 72. 0 73. 0 89. 2 B. Early-Season Control 24. 6 27. 3 30. 1 C. Late-Season Spray 48. 8 59. 4 91. 2 D. Late-Season Control 5. 1 7. 0 14. 5 The percentages in the above table were adjusted by arc sine transformation, and then subjected to an analysis of variance. Table 3 (page 43) and Table 4 (page 43) show the arc sine angles of percentages given in Table 2, and a summary of the analysis of variance. Results. It may be seen from the summary of the analysis of variance that highly significant differences among treatments occurred. A Studentized Range test was performed to indicate where these differences were. This test is made by taking values from a Studentized Range table 43 TABLE 3 1 ARC SINE TRANSFORMATION Treatments 1 B10?“ Totals Me ans A 58. 05 59. 69 70. 81 187. 55 62. 517 B 29. 73 31. 50 33. 27 94. 50 31. 500 C 44. 31 50. 42 72. 74 167. 47 55. 823 D 13.05 15. 34 22. 38 50. 77 16. 923 Totals 145.14 155. 95 199. 20 500. 29 1Values taken from Snedecor (1956). TABLE 4 SUMMARY OF THE ANALYSIS OF VARIANCE Source of Degrees of Sums of Mean F variation freedom squares squares Total 11 4, 657 Treatments 3 4, 052 l, 350. 67 41. 343** Blocks 2 409 204. 50 6. 260* Error (BXT) 6 196 32. 67 ** Significant at the 1% level. 31‘ Significant at the 5% level. 44 at the degrees of freedom of the error term, adjusting the table values, and comparing the adjusted values with the differences between treatment means. The range table values are adjusted by multiplying the standard deviation of the treatment means (3. 30) by the table values. The adjusted table value that is used for comparing treatment means depends upon the number of means that occur between those being compared, when all means are arranged in a numerical order. A line is placed over two or more treatment means when no significant differences occur between or among these means. The range test is outlined below: 2 3 4 5.24 5.51 5.65 (2) (3) (4) 17.292 18.183 18.645 16.923 35.500 55.823 62.517 15 8 6 ii I N V 1 1. -1 i, J 15 25 35 45 55 65 Distribution of the Treatment Means The above test shows that the early season spray (Treatment A) resulted in significantly greater mortality than occurred on the early- season control (Treatment B), or on the late-season control (TreatmentD). 45 The late-season Spray (Treatment C) resulted in highly significant mortality when compared with the early- and late—season controls. A highly significant difference also existed between the early-season control and the late-season control. This indicates that a large proportion of the natural mortality occurs during the early part of the growing season, when seedlings are very succulent. No significant difference occurred between the early-season spray treatment and the late-season spray treatment. It may be concluded from this that season of application of this silvicidal spray has little effect upon subsequent mortality of pine seedlings. A significant difference occurred among the block means also. Reference to the block totals in Table 5 will reveal that the mortality of pine seedlings in each plot of Block 3 was higher than in corresponding plots in any other block. The reason for this difference in mortality between Block 3 and the other blocks could not be deduced from the results of this investigation. 46 CHAPTER VI SUMMARY AND CONCLUSIONS Objectives of the Study. The rapid encroachment of undesirable hardwoods upon coniferous sites has stimulated considerable interest in the methods of eliminating such species. The application of silvicidal foliage sprays, from both ground and aerial equipment, has been very promising from the standpoint of cost and effectiveness. However, the use of foliage sprays may conceivably damage young coniferous seedlings, particularly during the early growing season when plants are very succulent. It was the purpose of this study to test the effects of foliage application of silvicides for hardwood control upon two-year-old short- leaf pine seedlings in the early growing season, and in the late growing season. Study Methods. An area with as uniform site conditions as could be found was selected for the study. The forest stand on the study area was primarily two-storied, with the upper story consisting of nearly mature pine and the understory consisting of mixed hardwood species. Many two-year-old shortleaf pine seedlings were growing beneath the hardwood canopy. The various treatments were assigned randomly to each of the three blocks. Spray application was made with a tractor-mounted boom-type spray unit at a rate of 40 gallons of oil-water emulsion 47 containing 2 pounds of 2, 4, 5—T acid, per acre: A. Early-season spray (June) B. Early-season control C. Late-season spray (August) D. Late-season control. Initial inventories of pine seedlings were made on ten one-tenth milacre subplots in each of the treatment plots and its cor- responding control at the time treatment was administered. Final inventories were made on all plots in December of the same year the spraying was completed. The percent mortality was computed for each treatment plot and control plot and subjected to arc sine transformation prior to analysis. The analysis of variance indicated that highly significant differences existed among plot means. These differences were isolated by utilizing the Studentized RAnge test. Conclusions. The mortality of the two-year-old pine seedlings was found to be greatly increased on all treatment plots as a result of silvicidal spraying. The early-season spray plots showed an average mortality of 78. 2 percent of the seedlings inventoried prior to treatment, compared to a natural mortality averaging 27. 4 percent in the corresponding control plots for the same period. 48 Plots sprayed in the late growing season showed an average mortality of 66. 2 percent of the seedlings inventoried prior to treat- ment, compared to a natural mortality of 8. 9 percent in the corresponding control plots for the same period. A mortality of 50. 8 percent greater than the natural mortality for the control plots occurred as a result of the early—season spray. The corresponding mortality for the late season spray was 57. 3 percent. The mortalities resulting from the two spray treatments are not significantly different from each other. The somewhat higher mortality occurring in the late-season spray treatment may have been partially due to higher air temperatures occurring in August. The natural mortality of pine seedlings on the early-season control plots was significantly greater, at the 1 percent level, than natural mortality on the late-season control plots. This suggests that a large portion of the natural mortality occurred during the early part of the summer, when the seedlings were more succulent. Natural mortality during the entire growing season was probably greater than is indicated in the early-season control plots, since considerable mortality more than likely occurred prior to the June inventory. Results of this study show that high mortality of young pine seedlings results from foliage spraying with the mixture and concentration of 2, 4, 5-T used. However, after the hardwoods are killed out, the number remaining could be regarded as sufficient to 49 provide for full stocking of the subsequent pine stand. If 80 percent mortality of pine seedlings resulted from foliage spraying on an area having 20, 000 seedlings per acre, the residual stocking of 4, 000 seedlings could possibly yield a fully stocked stand. If a large number of seedlings are not established on an area, foliage spraying could reduce the pine seedlings to an understocked level. Some hardwood control measures other than foliage spraying might be more suitable on areas where the pine seedling stocking is low. Need for Further Research. Considerable knowledge regarding the use of chemicals for controlling undesirable vegetation is available, but much is yet to be learned. More specific information concerning the minimum quantities of the different silvicides and different carriers necessary for killing plants of different species, sizes, ages, physiologic stages, and vigor is needed (Arend, 1959). The effects of these silvicides on desirable plants need to be more clearly defined. The exact reasons for differences in susceptibility of plants to these silvicides need to be determined. More knowledge is needed concerning the silvicidal effects and their relationship to soil moisture, soil type, soil fertility, time of day, time of year, tempera- ture, and humidity. More research is needed regarding the size and distribution of silvicide particles as applied by various methods and 50 by various types of equipment. The possibility of developing more suitable chemicals should not be overlooked. Lastly, more information is needed concerning the influence of hardwood control measures on esthetic values, wildlife, and water resources. 51 LITERATURE CITED American Chemical Products, Inc. 1959. Arend, J. 1953. Arend, J. 1955. Arend, J. 1959. “Mist Blowers, ” Field Observations. R and D No. 2, August 7. 4 pp. L. Scrub Aspen Control with Basal SpraLs. United States Department of Agriculture, Forest Service, Lake States Forest Experiment Station. Technical Note No. 401. l p. L. Tolerance of Conifers to Foliage Sprays of 2, 4-D and 2, 4, 5-T iniEbgver Michigan. United States Department of Agriculture: Forest Service, Lake States Forest Experiment Station. Technical Note No. 437. 2 pp. L. "Airplane Application of Herbicides for Releasing Conifers, " Journal of Forestry 57 (10): 738-749. Brender, E. V. and T. C. Nelson 1954. Behavior and Control of Understory Hardwoods after Clear Cutting a Piedmont Pine Stand. United States Department of Agriculture, Forest Service, Southeastern Forest Experiment Station. Station Paper No. 44. pp. 1-17. Burns, P. Y. 1959. ”Recommendations for Aerial Spraying of Hardwoods To Release Pines. " LSU Forestry Notes. Louisiana Agri- cultural Experiment Station. Note No. 28. 2 pp. Burns, P. Y., B. H. Box, and H. A. Nation 1959. ”Comparison of Herbicides in Aerial Spraying for Pine Release in Northwestern Louisiana. " LSU Forestry Notes. No. 29. 2 pp. Campbell, R. S. and F. A. Peevy 1950. "Chemical Control of Undesirable Southern Hardwoods. " Journal Range Management. 3: 118-124. Carlson, A. E. 1950. "Controlling 'Forest Predators'. ” American Forests. 56 (8): 20-21, 43. 52 Cassady, J. T. and W. F. Mann Jr. 1954. The Alexandria Research Center. United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. 49 pp. Chaiken, L. E. 1951. The Use of Chemicals To Control Inferior Trees in the Management of Loblolly Pine. United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. Station Paper No. 10. 34 pp. Clark, F. B. and F. G. Liming. 1953. Sprouting of Blackjack Oak in tthissouri Ozarks. United States Department of Agriculture, 1 Forest Service, Central States Forest Experiment Station. Technical Paper 137. 2 pp. Coile, T. S. 1949. "Effect of Soil on the Development of Hardwood Understories in Pine Stands of the Piedmont Plateau. " Soil Science Society Proceedings. pp. 350-352. Coulter, L. L. and R. A. Ralston 1954. Aerial Spray Tests with 2, 4, 5-T for Scrub Oak Control in Lower Michigan. United States Department of Agriculture, Forest Service, Lake States Forest Experiment Station. Technical Note No. 424. 1 p. Crafts, A. S. 1953. ”Herbicides. ” Annual Review of Plant Physiology. 4: 253-282. Darrow, R. A. 1956. ”Control of Post and Blackjack Oak and Other Brush by Aerial Spray Applications of Herbicides. " Proceedings of the Fifth Annual Texas Agriculture Aviation Conference. College Station (Fl—F4). Davis, J. R. 1958. ”Basal Spray with 2, 4, 5-T for Winter Hardwood Control in East Texas. ” Journal of Forestry. 56(5): 349. Day, M. W. 1948. "The Chemical Control of Certain Forest Shrubs: A Progress Report. ” Michigan Agricultural Experiment Station. Quarterbr Bulletin. 30(4): 427-436. 53 Day, M. W. 1950. ”How To Control Undesirable Trees and Shrubs. " Michigan Agricultural Experiment Station. Quarterly Bulletin. 32(4): 486-491. Day, M. W. 1956. Demmon, 1951. Ferguson, 1955. Furnival, 1954. Gantz, R. 1959. Goodrum, 1956. How To Control Undesirable Trees and Shrubs with Chemicals. Michigan State University Cooperative Extension Service. Extension Folder F-182 (Revised). 5 pp. E. L. Forest Research in the Southeast. United States Department of Agriculture, Forest Service, Southeastern Forest Experi- ment Station. Station Paper No. 13. 11 pp. E. R. and G. K. Stephenson. Pine Regeneration Problem in East Texas: A Project Analysis. United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. Occasional Paper 144. 72 pp. G. M. “Deadening Culls in Bottomland Hardwood Stands. " Southern Lumberman. 189(2369):123-124. L. "New Developments in Brush Control. ” Agricultural Chemicals. (June issue). p. 60. P. D. and V. H. Reid. Transactions of the Twenty-First North American Wildlife Conference. pp. 127-141. Gr atkow ski, H. 1959. Grano, C. 1953. Effects of Herbicides on Some Important Brush Species in Southwestern Oregon. United States Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experi- ment Station. Research Paper No. 31. 33 pp. X. ”Chemical Control of Weed Hardwoods. ” Southern Lumberman. 186(2332): 46-47. 54 Harrington, T. A. 1958. "Release Doubles Shortleaf Seedling Growth. " United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. Southern Forestry Notes. No. 113. 4 pp. Harrington, T. A. 1959. ”2, 4, 5-T Effective from Helicopter.."' United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. Southern Forestry Notes. No. 124. 4 pp. Hawkes, C. 1953. "Planes Release Tree Plantation. " Journal of Forestry. 51: 345-348. Hedrick, D. W., H. H. Biswell, and A. M. Schultz 1953. ”Response of Brush Seedlings to Sprays of 2, 4-D and 2, 4, 5—T on Burned Chamise Areas. ” California Fish and Game. 39(4): 497-505. Hough, A. F. 1950. Weed Killers May Be Useful in Reforesting Old Burns. United States Department of Agriculture, Forest Service, Northeast Forest Experiment Station. Research Note No. l. 4 pp. Huckenpahler, B. J. . 1954. “Poisoning Versus Girdling To Release Underplanted Pines in North Mississippi. ” Journal of Forestg. 52(4) 266-268. lkenberry, G. I., H. D. Bruce and J. B. Curry 1938. ”Experiments with Chemicals in Killing Vegetation on Fire- breaks. ” Journal of Forestry. 36: 507-515. Jankowski, E. J. 1955. Effectiveness of Chemical Sprays on Resistant Species. United States Department of Agriculture, Forest Service, Lake States Forest Experiment Station. Miscellaneous Report No. 39. pp. 7-12. Leonard, O. A. 1956. . Chemical Control of qudy Plants in California. California Agricultural Experiment Station Bulletin 755. pp. 1-40. 55 Little, A. and J. J. Mohr. 1956. Chemical Control of Hardwoods on Pine Sites of Maryland's Eastern Shore. United States Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. Forest Research Note No. 64. 4 pp. Lotti, T. 1957. An Effective Control for Cull Hardwoods. United States Department of Agriculture, Forest Service, Southeastern Forest Experiment Station. Research Note No. 108. 2 pp. Lutz, H. J.) and R. F. Chandler, Jr. 1946. Forest Soils. John Wiley and Sons, Inc. , N. Y. (Fifth printing, 1951). 514 pp. Mann, W. F. Jr. 1951. l‘Profits from Release of Loblolly-Shortleaf Pine Seedlings. " Journal of Forestry. 49(4): 250-253. McConkey, T. W. 1958. Helicopter. Spraying with 2, 4, 5-T To Release Young White Pines. United States Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. Station Paper No. 101. 14 pp. McQuilkin, W. E. 1957. Frill Treatment with 2, 4, 5-T and 2, 4-D Effective for Killing Northern Hardwoods. United States Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. Station Paper No. 97. 18 pp. Nichols, J. M. 1952. ”Basal Bark and Frill Treatment of Pole-Size Post Oak and Hickory. ” North Central Weed Control Conference. Ninth Annual Research Report. p. 60. Potts, S. F. 1958. Concentrated Spray Equipment. Dorland Books. Caldwell, New Jersey. 598 pp. Ray, H. C. 1958. ”Aerial Chemical Reduction of Hardwood Brush as a Range ' Improvement Practice in Arkansas. ” Proceedings of the Society of American Foresters. pp. 201-205. Reynolds, 1947. Reynolds, 1951. Roe, E. I. 1957. 56 R. R. ”Management of Second-Growth Shortleaf-Loblolly Pine Hardwood Stands. ” Journal of Forestry. 45(3): 181-187. R. R. "Timber Stand Improvement Job in Southwest Arkansas. " Southern Lumberman. 185(2289): 43-45. Aerial Sprying of Upland Brush before Planting Effectively Reduces Need for Plantation Release. United States Depart- ment of Agriculture, Forest Service, Lake States Forest Experiment Station. Technical Note 502. 2 pp. Rogers, N. F. 1958. Rudolf, P. 1951. Rudolf, P. 1956. Schubert 1955. Silker, T. 1956. Sluder, E. 1958. Airplane—Sprayed Herbicides Release Shortleaf Pine from Hardwoods. United States Department of Agriculture, Forest Service, Central States Forest Experiment Station. Station Note No. 117. 2 pp. O. Chemical Control of Brush and Tree Growth for the Lake States. United States Department of Agriculture, Forest Service, Lake States Forest Experiment Station. Miscel- laneous Publication No. 15. 30 pp. 0. and R. F. Watt Chemical Control of Brush and Trees in the Lake States. United States Department of Agriculture, Forest Service, Lake States Forest Experiment Station, Station Paper No. 41. 58 pp. 7 G. H. Recent Trials with 2, 4-D and 2, 4, 5-T To Kill Brush in the Sierra Nevada in California. United States Department of Agriculture, Forest Service, California Forest and Range Experiment Station. Forest Research Note No. 102. 7 pp. H. and R. A. Darrow Hardwood Control and Increased Forage Production in Scrub Hardwood-Pine Stands Treated with Aerial Applications of 2, 4, 5-T and Silvex. Texas Agricultural Experiment Station. Progress Report No. 1852. 5 pp. R. Control of Cull Trees and Weed Species in Hardwood Stands. United States Department of Agriculture, Forest Service, Southeastern Forest Experiment Station. Station Paper No. 95. 13 pp. Smith, J. 1958. Smith, J. 1959. Smith, J. 1959. Smith, J. 1960. Snedecor, 1956. 57 L. Effect of Hardwood Removal on Available Moisture and Growth in Young Pine Stands. Progress Report. United States Department of Agriculture, Southern Forest Experiment Station (Unpublished). L. "2, 4, 5-T Concentrations for Tree Injections in the Arkansas Ouachitas. " United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. Southern Forestry Notes. No. 123. 4 pp. L. and E. R. Lawson "Sampler for Gravelly Plastic Soils. ” Soil Science. 88(1): 56-57. L. and E. R. Lawson "Herbicidal Sprays Damage Pine Seedlings. " United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. Southern Forestry Notes. No. 125. 4 pp. G. W. Statistical Methods. Iowa State Press. 534 pp. (Table on pp. 318-319). Stephenson, G. K. and C. B. Gibbs 1959. Stransky, 1959. Sutton, R. 1958. Selective Control of Cull Hardwoods in East Texas. United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. Occasional Paper 175. 10 pp. J. J. “Concentrated or Diluted 2, 4, 5-T as a Supplement to Girdling ?" Journal of Forestry. 57(6): 432-434. F. Chemical Herbicides and Their Uses in Silviculture of Forests of Eastern Canada. Department of Northern Affairs and Natural Resources, Forestry Research Division. Tech. Note No. 68. 54 pp. United States Department of Agriculture, Forest Service 1958a. Timber Resources for America's Future. Forest Resources Report No. 14. 713 pp. United States Department of Agriculture, Forest Service 1958b. Annual Report. Southeastern Forest Experiment Station. Station Paper No. 22. 50 pp. 58 United States Department of Commerce, Weather Bureau 1958. Climatological Data for Arkansas. Volume 64, Nos. 1-12. United States Department of Commerce, Weather Bureau 1959. Climatological Data for Arkansas. Volume 65, Nos. 1-12. United States Department of Commerce, Weather Bureau 1959b. Climates of the States. Climatography of the United States. No. 60-3. Walker, L. C. 1956. Controlling Undesirable Hardwoods. Georgia Forest Research Council. Report No. 3. 24 pp. Zahner, R. 1958. ”Hardwood Understory Depletes Soil Water in Pine Stands. ” Forest Science. 4(3): 178-184. APPENDIX 59 DAILY PRECIPITATION RECORD FOR 19581! TABLE 5 60 Day Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 1 .04 1.74 .63 2 2.16 .09 3 1.00 2.25 4 5 .29 .03 .40 .02 6 .32 .22 7 .85 .57 8 .55 .01 1.24 9 .59 1.70 .01 .21 10 .12 .12 .09 .52 .01 11 .07 .13 .12 1.15 12 .46 .21 13 .45 .32 .45 .05 .96 14 .43 .76 3.02 15 .05 .02 .08 .46 .16 1.57 16 .46 .01 .47 .21 17 .28 1.52 .20 .32 18 .05 .25 .32 19 .02 .60 .27 1.35 .02 20 2.69 1.28 .02 .28 21 .22 .36 .44 .10 22 .01 .02 .11 .28 2.00 23 1.85 .11 .20 24 .52 .03 25 .05 .04 .05 .52 .21 26 .27 .22 1.32 1.07 .75 .05 .15 27 .04 1.60 .05 .29 28 .01 .05 .14 1.22 29 .25 .29 .13 30 .07 .05 .02 .68 31 .07 .12 TknalEL49 1.08 5.87 ,7.41 8.64 4.18 3.36 3.52 4.43 2.59 6.90 1.88 ‘ 'Iotal 53.35 1Data taken from the Hot Springs Station (1 mile NNE) of the Climalological Data for Arkansas, Weather Bureau, U. S. Department of Commerce. All precipitation values are in inches. 61 TABLE6 DAILY PRECIPITATION RECORD FOR 1959-1-/ Day Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 1 .02 .01 1.03 .63 .11 2 .06 .13 3 .32 4 .18 .01 .86 1.20 1.22 5 1.25 .38 .09 6 1.07 7 .04 .03 8 .22 .16 .02 .66 .12 1.19 .04 .01 9 .01 .07 .19 .11 4.41 .08 .64 .02 10 .03 .02 .04 .36 .41 .45 11 .84 .07 .01 .76 .10 .20 3.32 12 .51 .16 .07 .36 .62 13 1.88 .01 1.13 .63 14 4.34 .08 .39 15 1.32 .29 .01 .31 16 2.12 1.91 17 .70 .13 1.34 .93 18 .01 .05 .34 19 .ll .35 .07 .15 20 .02 .ll 21 .05 .93 .31 .08 .02 22 .80 .74 .41 .35 23 .23 .07 .06 .06 24 .72 .74 .50 25 .04 .01 .16 .13 1.53 26 .60 .07 .26 1.92 .36 27 .01 .01 .03 .40 .09 .90 28 .28 .08 .10 29 .07 1.24 30 .13 .25 .52 31 .17 .03 'Totalla86 8.68 4.17 3.51 2.04 8.89 6.68 1.63 6.53 3.41 2.46 9.25 Total 59. ll 1Data taken from the Hot Springs Station (1 mile NNE) of the Climato- logical Data for Arkansas, Weather Bureau, U. S. Department of Commerce. All precipitation values are in inches. 62 TABLE 7 RELATIVE SUSCEPTIBILITY OF VARIOUS SPECIES 1 TO 2, 4-D AND 2, 4, 5-T Alder Birch 2 Blackberry (2, 4, 5-T only) Black cherry Black gum Black haw Black locust Boxelder Ceonanthus Cherry Chinaberry Cucumber tree Elder Elm Grape Hawthorn Hazel Honeysuckle Ironwood Manzanita Osage-orange Plum, wild Poison ivy Post oak Sassafras Spice bush Southern red oak Sumac Sweetgum White oak Willow Witch hazel Yellow poplar Susceptible Specie s Alnus spp. Betula spp. Rubus spp. Prunus serotina Ehrh. Nyssa silvatica Marsh. Viburnum spp. Robinia pseudoacacia L. Acer negundo L. Ceonanthus spp. Prunus spp. Melia asedarach L. Magnolia accuminata L. . Sambucus spp. Ulmus spp. Vitis spp. Crataegus spp. Corylus spp. Lonicera japonica Thunb. Carpinus caroliniana Walt. Arctostaphylos spp. Maclura pomifera (Raf. ) Schneid. Prunus spp. Toxicodendron radicans L. Quercus stellata Wangenh. Sassafras albidum (Nutt. ) Nees Benzoin aestivale Nees Quercusfalcata Michx. Rhus spp. Liquidambar styraciflua L. Quercus alba L. Salix spp. Hamamelis virginiana L. Liriodendron tulipifera L. 63 TABLE 7 (continued) Resistant Species Ash Fraxinus spp. Aspen Populus spp. Basswood Tilia americana L. Beech Fagus grandifolia Ehrh. Blackjack oak Quercus marilandica Muenchh. Black oak Quercus velutina Lam. Blackberry Rubus spp. Bur oak Quercus macrocarpa Michx. Canyon liveoak Quercus chrysolepis Liebm. Cottonwood Populus deltoides Bartr. Dogwood Cornus spp. Eastern redc edar Golden chinkapin Juniperus virLiniana L. Castanopsis chrysophylla (Hook.)D. C. Gooseberry Ribes spp. Greenbriar Smilax spp. Hackberry Celtis spp. Hawthorn2 Crataegus Ispp.‘ Hickory Carya spp. Holly Ilex qpaca Ait. Hornbeam Ostrya virginiana (Mill) _K. Koch. Laurel Kalmia latifolia L. Lilac Syringa vulgaris L. Live oak Quercus virginiana Mill. Maple Acer spp. 1 Northern red oak Quercus borealis Michx. f. Persimmon Diospyros virggniana L. Pine Pinus spp. Prickly ash Xanthoxylum americanum Mill. Red maple Acer rubrum L. Rhododendron Rhododendron maxima L. Rose, wild Rosa spp. Serviceberry Amelanchier spp. - Scarlet oak Scrub oak Quercus coccinea Muenchh. Quercus ilicifolia Wang. Sourwood Oxydendrum arboreum (L.) D. C. Southern red oak Quercus falcata Michx. Sycamore Platanus occidentalis L. Tanoak Lithocarpus densiflorus (Hook. 8.: Arn. ) Rehd. 64 TAB LE 7 (continued) Turkey oak Quercus laevis Walt. Water oak Quercus nigra L. Winged elm Ulmus alata Michx. 1This list has been compiled from the works of Day (1950), Burns (1959a), Walker (1956), Lotti (1957), Day (1956), Gratkowski (1959), and others. It should be remembered that many factors may influence the reaction of a plant to a phytocide, and that different phytocides may yield different results. For these reasons, the data given in this table should not be assumed to be correct in all chemical applications. 2The relative susceptibility of these species was found to be conflicting. TABLE 8 SEVERAL HORMONE - T YPE PHYTOCIDES1 65 2, 4-D Chipman 2, 4-D, Low Vol. Ester Esteron Ten-Ten (Dow) Esteron 44 (Dow) Weedone (Amer. Chem. Prod. , Inc. )2 2, 4, 5-T Blackleaf 2, 4, 5-T Brush Killer Bramblcide E- 2, 4, 5-T (Thompson) Brush-Rhap-4 (Reasor-Hill) Dow 2, 4, 5-T Amine Weed Killer Ded-Weed T-5 (Thompson-Hayward) Diamond Brush Killer Lo V-4-T DuPont 2, 4, 5-T Ester Brush Killer, Low Vol. Esteron 2, 4, 5-T (Dow) Esteron 245 OS (Dow) General Chemical Low Volatile 2, 4, 5-T Brush Killer Gold Bear 55 (Swift) Inverton 245 (Dow) Monsanto 2, 4, 5-T Low Vol. Ester Brush Killer Ortho Brush Killer (Calif. Spray) Pittsburg Brush Killer Low Vol. No. 4 1 . ' . . This list is not complete, nor does it imply endorsement by the writer. The manufacturer's name appears in parentheses if it is not given with the commercial name of the chemical. 2Formerly American Chemical Paint Company. 66 TAB LE 8 (continued) Stull Low Vol. Brush Killer Trelease (Amer. Chem. Prod. , Inc.) Veon 100 Amine (Dow) Veon 245 (Dow) Weedar 2, 4, 5-T (Amer. Chem. Prod. , Inc.) Weedone 2, 4, 5-T (Amer. Chem. Prod. , Inc.) Weedone L-329-T (Amer. Chem. Prod. , Inc.) Weedone 2, 4, 5—T Propionic (Amer. Chem. Prod. , Inc.) Huron (Dow) Silvex (Dow) 2, 4-D and 2, 4, 5-T Combinations Brush-Rhap 2-2 (Reasor-Hill) Chemagro Brush Killer 22 Chipman Low Volitile Brush Killer Diamond 10-20 Estercide TD-2 (Calif. Spray) Esteron Brush Killer (Dow) General Chemical Low Volatile 2-2 Brush Killer Gold Bear 2-2 Brush Killer (Swift) Monsanto Brush Killer 2, 4-D-2, 4, 5-T Patterson's Brush Killer No. 400 (Pearson-Ferguson) Veon BK (Dow) Weedar Amine Brush Killer (Amer. Chem. Prod. , Inc.) Weedone Brush Killer 32 (Amer. Chem. Prod. , Inc.) Weedone Brush Killer 64 (Amer. Chem. Prod. , Inc.) Weedone Industrial Brush Killer (Amer. Chem. Prod. , Inc. ) TABLE 9 A SUMMARY OF SEEDLING INVENTORIES Block I Early Season Spray Early Season Check 1 l l l (1) (Z) (3) (4) (1) (Z) (3) (4) A 7 4 3 A 9 3 6 B 15 2 13 B 6 3 3 C 5 3 2 C 18 14 4 D 7 3 4 D 13 11 2 E 7 2 5 E 8 6 2 F 26 14 12 F 25 24 l G 14 l 13 G 23 17 6 H 26 1 25 H 19 14 5 I 20 12 8 I 5 0 5 J 23 0 23 J 16 15 1 Totals 150 42 108 Totals 142 107 35 Block 11 ' Early Season Spray Early Season Check (1) (2) (3) (4) (1) (Z) (3) (4) A 12 b 12 A 9 3 6 B 13 0 13 B 25 21 4 C 9 2 7 C 11 ll 0 D 18 6 12 D 11 10 1 E 16 3 13 E 9 6 3 F 11 3 8 F 18 13 5 G 13 1 12 G l5 l4 1 H 30 6 24 H 23 15 8 I 21 14 7 I 13 12 l J 9 6 3 J 16 4 12 Totals 152 41 111 Totals 150 109 41 TABLE 9 (continued) Block III Early Season Spray Early Season Check 1 l l l (1) (2) (3) (4) (1) (Z) (3) (4) A 5 0 5 A ll 5 6 B 13 2 11 B 11 4 7 C 13 0 13 C 9 5 4 D 15 4 11 D 10 5 5 E 8 1 7 E 9 8 1 F 14 O 14 F 31 30 1 G 10 2 8 G 11 8 3 H 10 O 10 H 23 13 10 I 30 0 30 I 17 11 6 J 39 8 31 J 11 ll 0 Totals 157 17 140 Totals 143 100 43 Block I Late Season Spray Late Season Check (1) (2) (3) (4) (1) (2) (3) (4) A 51 4O 11 A 19 19 0 B 8 l 7 B 15 15 0 C 21 9 12 C l6 l3 3 D 7 5 2 D 18 17 l E 11 6 5 E 15 12 3 F 9 4 5 F 19 19 0 G 17 10 7 G l4 l4 0 H 10 2 8 H 15 15 0 I 17 3 14 I 12 12 0 J 15 5 10 J 13 12 1 Totals 166 85 81 Totals 156 148 8 69 TABLE 9 (continued) Block 11 Late Season Spray Late Season Check 1 l l l (1) (Z) (3) (4) (1) (2) (3) (4) A 12 2 10 A 10 10 0 B 19 2 17 B 20 19 l C 24 15 9 C 15 15 0 D 15 5 10 D 10 7 3 E 18 10 8 E 20 20 0 F 25 14 11 F 12 12 0 G 15 11 4 G 16 15 1 H 12 2 10 H 15 13 2 I 12 4 8 I 15 14 1 J 8 O 8 J 24 21 3 Totals 160 65 95 157 146 11 Block 111 Late Season Spray Late Season Check (1) (Z) (3) (4) (1) (2) (3) (4) A 13 2 11 A 36 32 4 B 16 0 16 B 11 7 4 C 23 0 23 C 14 14 0 D 15 0 15 D 13 10 3 E 16 l 15 E 16 12 4 F 13 1 12 F 11 10 1 G 9 4 5 G 15 15 0 H 10 4 6 H 16 10 6 I 20 2 18 I 18 18 0 J 24 0 24 J 15 13 2 Totals 159 14 145 Totals 165 141 24 Column (1) represents the subplot designations. Column (2) is the original or initial seedling inventory of each subplot. Column (3) is the final seedling inventory or the number of seedlings living at the end of the growing season. Column (4) is the seedling mortality, which was obtained by subtracting the final inventory from the initial inventory. The above designations apply to all columns throughout the table. I '1 11 1 I1 5 15 Ill 1 '0 5 5 ll 5 5 5 ll :5 6987