IL34979A - Aquatic herbicides having a synergistic effect - Google Patents

Description

Aquatic herbicides having a synergistic effect aiSBESOiA HOTS AID MAMFASTO co &m AQUATIC HERBICIDE According to the present invention there are provided aquatic herbicides having a synergistic effect, when used together, irt controlling the growth of undesirable aquatic plants. More particularly there are provided compositions which may be used synergistically for controlled release of herbicidal materials when introduced into water.

Aquatic herbicides are commonly added to an aquatic environment either in a soluble or emulsified form or as dense granules that sink directly to the bottom of the lake or pond where they disintegrate In various ways to release copious amounts of herbicide into the water„ In either case, the entire aquatic environment becomes contaminated with herbicide to a concentration level that is equal to or greater than the lowest lethal concentration (LLC) required to kill the unde-sired species. Usually a large excess must be added to maintain this level locally because of solubility, natural diffusion and water currents that exist in lakes and ponds. An example of such a herbicide is copper sulfate, which is commonly used to treat aquatic algae. The compound is very soluble, resulting in toxicity in areas other than those that are infested.

Moreover, herbicides used presently require a relatively large dosage even in the desired localized areas to be treated which has adverse effects on desired aquatic life in those areas.

It is highly advantageous to contaminate only the surface space In the immediate vicinity of the undesired aquatic species, leaving the remainder of the aquatic environment essentially unccntaminated for use by preferred aquatic species. It is also advantageous to localize application to given target areas without serious contamination by drift 1P and diffusion to adjacent areas. It is perhaps most advantageous to acquire a local control of undesirable aquatic species with a very small amount of toxicant to lower further any chances of toxicity to desirable aquatic life both in the treated area and over a much broader area.

Further, existing products do not control a sufficiently large percentage of common aquatic weeds, especial3y algae . To produce a relatively broad spectrum herbicide, high dosages of both herbicides and algicides are required which increase water pollution and toxicity to desirable aquatic life,, Complex aquatic weed problems frequently require multiple treatments with different herbicides and even then, rapid weed regrowth is frequently encountered,, Some products such as copper sulfate are corrosive to pumping and spraying equipment and may also be toxic or hazardous to the applicatore At present, there is not a broad spectrum, low toxicity, slowly releasable aquatic herbicide known to applicant.

Methods are known for treating pesticides, such as insecticides or herbicides, to bring about slow release of the active material. Such slow release compositions have been produced by encapsulation in slowly soluble materials, dilution with an inert material as b^ adsorption ~>n sand or clay, mixing with a water-Insoluble resins etc. Such compositions function chiefly by control of diffusion in a mechanical way. The density of the carrier in these formulations is such that the particles sink rapidly to the bottom without adhering to the plant foliage which is distributed throughout the bulk of the water.

It has been found that the efficacy of water-soluble herbicides can be improved significantly if the herbicide is reverslbly preadsorbed In its ionic form by ion-exchange processes on an ion-exchange material which is itself particulate or has been coated or deposited onto an inert particulate material having a density slightly greater or less than water„ In some instances, the ion-exchange material and herbicide can be coated on the inert particulate material together. When applied to an aquatic system, e.g. for control of undesirable plants, the particles settle through the aqueous medium without significant loss of the adsorbed herbicide and come to rest on plant surfaces distributed randomly throughout the bulk volume of the water0 The herbicide is then released slowly by ionic exchange processes at a rate approaching that at which the plant can absorb the herbicide or a period of time long enough to cause the death of the plant. The herbicide charge carried by the particles is limited^ so that the supply is exhausted soon after the aquatic species becomes moribund. The desorption rate of herbicide from the particle in contact with the plant can actually be increased by virtue of its location. The plant expires CQ2 which combines with water to give HCO^" Ion which in turn liberates herbicide by anion exchange processes to help maintain the lethal surface condition. The rate of desorption is slower in distilled water than in lake water which has dissolved anions.

It has further been found that the use of substantially insoluble copper-containing compounds effectively controls many undesirable aquatic plants when used in very small amounts.

Soluble copper compounds have been used heretofore but, because of their soluble nature, had to be used in large amounts to effectively control aquatic weed growth in one particular area. Consequentl 5 the whole aquatic area involved was permeated with copper causing damage to desirable plants, fish and wildlife. Insoluble copper containing compounds do not permeate the entire aquatic environment but are active only at the plant site. The particles are allowed to settle down through the water until they reach a plant surface. The particles are held by the plant or "cling" thereto as in the case of filamentous plants. At this point there is a very slow dissolution of copper ions into the previously copper-free area at the plant surface. As a small amount of copper ion is released, it is absorbed by the plant causing additional copper ions to be slowly released.

Where the substantially water insoluble copper compounds and ion-exchange held herbicides are used together, it was found that a synergistic effect in controlling unwanted aquatic life was produced. Synergism is used herein in its normal sense as the simultaneous effect of separate agencies which, together, have greater total effect than the sum of their individual effects. The resulting synergistic effect allows smaller amounts of the two compounds to be used together to effectively control a wide spectrum of unwanted aquatic plants with minimal water pollution and toxic effects to desirable marine life. As both herbicides are released slowly at the plant surface, only the immediate surroundings to the plant surface in contact with the particles contain a concen-tration above the lowest lethal concentration (LLC) with respect to herbicide. The bulk of the water remains safe for use by desirable species, such as fish and humans. This ability to kill plants without wasteful and dangerous over-treatment is a definite economic, as well as a biologic advantage. Moreovers the distribution pattern of the particles in their downward progress is such that only the plants in the area treated are affected by the slow release of toxicant.

Drift is minimized and plants growing in adjacent areas continue to fluorish.

Ion exchange materials which are useful in the process of this invention include various inorganic materials. Aluminum hydroxide is especially suitable because of its amphoteric character and its relatively low cost. Other metallic hydroxides such as magnesium hydroxide, zinc hydroxide, ferric hydroxide, copper hydroxide, the basic salts of calcium and barium, as well as insoluble polymeric organic quaternary amines, such as crosslinked polymeric quaternized polyvinyl pyridines and polyvinyl aminostyrenes can also be used on the particulate carrier to produce a surface layer or coating for adsorption of the toxic agent.

The inorganic materials are preferable, since they are cheaper and they minimize the amount of foreign organic additives that consume dissolved oxygen by biodegradation and may possibly produce soluble degradation products that are objectionable or even harmful to human and animal life.

Silicious materials such as clays, micas, vermiculites and most soils are cationic surfaces which suggest their application for controlled release of cationic herbicides, such as l,l'-dimethyl- , '-bipyridinium dibromide (hereinafter compound IX). Unfortunately, these materials have too great an affinity for cations, and desorption is virtually impossible before normal degradation occurs. For these materials to be used as such as carriers, it is necessary to cause them to absorb a several-fold greater amount of herbicide than that required to saturate the surface capacity for cation. This is economically ■A wasteful since much of the herbicide charge can never be released to control aquatic vegetation. In fact, suspensions of these silicious materials in water render normal treatment with soluble cationic herbicide ineffectual because of the rapid rate at which these suspensoids remove the cationic herbicides from solution.

It has been found, however, that the affinity of these silicious materials for cations is decreased considerably by prior surface treatment thereof with ΑΙ^Η)^· Cationic herbicides adsorbed on A1(0H) , or Al(0H) coated surfaces 3 ~* of clays, micas, vermiculites, etc. are retained sufficiently well to prevent significant desorption during sedimentation, but the desorption rate is fast enough to make these materials useful compositions of the invention.

The result of coating the particulate material with ion-exchange agent, which is then treated with the herbicides, is that the formulation is carried through the aquatic medium within a reasonable time interval, without significant loss of herbicide, to the target area where it clings to the surface to be treated. The geometry and size of the particles are selected to be such that the force of adhesion is greater than the forces due to gravity or to ambient water currents.

A variety of particulate materials can be modified to afford surface anion exchange properties. Some of these are hydrobiotite, vermiculite, sand, talc, kaolin, titanium dioxide, clays, bentonite, mica, Aerosil (extremely light SiO^), glass microspheres and perilte. Substantially any water-insoluble material can be used so long as it can be coated with the ion-exchange agent and holds the same against removal by water.

Hydrobiotite is a mic ceous material made by replacing potassium in biotite with e,g, as described in The American Mineralogist, V. 26, No. 8 pp 278-484, 19 1.

The choice of these substrates can be made in accordance with the intended use, Thus, for slow release at the bottom of a body of water, material with a high bulk density such as sand, clays, mica or pelletized particulate hydrobiotite or vermiculite would be chosen for rapid sedimentation. For surface treatment lighter materials, such as expanded vermiculite, perlite and glass spherical micro-balloons would be preferred. For treatment of aquatic vegetation distributed randomly throughout the aquatic space, material with intermediate density, such as finely ground expanded hydrobiotite or vermiculite, would be more suitable. When needed, from the standpoint of capacity, and where applicable, from the standpoint of sedimentation rate, it is possible to use the anion exchange material per se as the carrier without the inert substrate.

The sedimentation rate and the ability to cling to surfaces of aquatic vegetation can be modified beneficially by the use of additives, such as polyvinyl alcohol or hydroxyeth l cellulose, (e.g. that available under the tradename Vistik) « If it is desired, it is possible to coat these particles with the organic polymers to slow the rate of desorption even further.

The metal hydroxides used as ion-exchange coatings are conveniently coated upon the surface of the selected inert particulate material by precipitation of the hydroxide in an aqueous slurry of the particles. This can be done in various ways as indicated below by the following representative equations (1) Neutralization of soluble alkaline form0 Ex.· NaA102 + HZ + HOg >Al(OH)3 + NaZ where HZ is any inorganic acid, such as HC1, H2SCV HN03* or any orSanic acid with car- boxylie, sulfonic or phosphoric acid groups. (2) Neutralization of soluble acid form.

Exs A1X3 + 3NaA + 3^0,^—*A1(0H)3 + 3NaX + 3HA where X is an anion of a strong acid, such as Cl~~; Br~, N0~ , or a mixture of such anion and QH, and A is either OH or anion of a weak acid, such as acetic, benzoic, and the like.

The thickness of the hydroxide coating is a function of the ratio of the amount of metal hydroxide produced to the available surface of inert particulate substrate charged to the mixture„ The metallic hydroxide coatings may retain some of the anions used to effect the neutralization, without significant loss of exchange capabilities,, The composition of the coating is thus, e0g„ really AlCOHj^ ^ where X represents various anions exchanged from solution. The magnitude of this absorption (n) is proportional to the final concentration as determined by the equilibrium constants at the pH in question,, If desired, it is possible to neutralize NaA102 as in method 2 above with the acid form of the herbicide in question or an inorganic acid can be used for neutralization followed by anion exchange with the desired herbicide, either in the same solution or after the solid has been collected by filtration and re-slurred in the second solution, The ion-exchange reaction which is used to incorporate the herbicide into the lon-exchange material is the replacement of OH by inorganic or organic anions. This is a general reaction as indicated below; Al(xOH)'3-n n + mZ~—»Α1(0Η)'3-- Z mXn + mOH ~ Replacement of adsorbed anions rather than OH also occurs concomitantly with the above reaction.

Al(OH)3„nXn + mZ^Al(OH)3_nX(n_m)Zm + mX ~ The relative rates of these alternative reactions are determined by the relative affinities of the ions in question for the metallic hydroxide substrate„ Visible evidence of the general nature of this reaction is given by color adsorption using anions, such as O^-, CrO^-or organic dyes with attached -OH, -C02H, -SO3H or groups as exemplified by eosln, fluorescein, methyl orange and the like.

These dye anions are desorbed slowly by repeated extraction with distilled water. The rate of desorption is increased by the presence of salts in accordance with known principles of ion exchange.

The use of dye-bearing particles is useful as a visual aid in the denervation of treated areas. Thus, little dye was lost when the particles were allowed to settle in a gallon tank filled with lake water. Within a day, however, a colored layer ¾ to inch (.64 to 1.77 cm) thick developed over the bottom of the tank where the particles came to rest. When the tank was furnished with growing plants and the sedimentation experiment repeated, the colored layer appeared in the vicinity of the particles resting on the plant (as we'll as on the bottom), and the concentration of dye decreased outward laterally and downward from the leaves into the bulk i of the water0 Similarly, particles added to run-off water in a field imparted no detectable color to the water stream except to the area where the particles ultimately accumulated In quiet pools.

Anions which are particularly useful for control of aquatic vegetation are 7-oxabicyclo 2"02ej7 heptane-2, 3-dicar-boxylate (l), 2,4-dichlorophenoxyacetate (II ), 2- (2 4,5-trichlorophenoxy)-propionate (ill), trichloroacetate (IV), 2,2-dlchloroproplonate (V), 4-amlno-3, 5, 6-trichloropyridine-2-carbox late (VI ), arsenite (VII) and the like0 They may be represented by the formulae s The sodium or potassium salts of anions I, II, III, IV, V and VI are also known commercially by common and trademark nair.es, eeg0 endothall (Aquathol), 2,4-D silvex (Aqua-Vex), TCA, dalapon (Radapon) and picloram (Tordon), respectively.

The common names refer to compounds of the parent acids.

Cations which are particularly useful for control of aquatic vegetation includes 1, l'-ethylene^S'-bipyridlnium (VIII), l,l'-dimethyl- , ,-bipyridinium (IX), e.g.

VIII IX and cupric io 0 The bromide and chloride salts of cations VIII and IX are known commercially by the trademark names Dlquat and Paraquat, respectively.

Each compound is added to control a finite set of living plants which have specific sensitivity to the compound in question,, The choice of herbicide to be adsorbed on the ion-exchange surface is determined by the species to be eradicated 0 In areas Inhabited by several undesirable species sensitive to different herbicides it will be necessary to use two or more adsorbed ionic herbicides. In this respect, combinations can include anionic and cationic materials.

Where necessary, neutral herbicides, such as 2, 6-dichlorophenyl cyanide (Casoron) or the esters of 2,4-dichlorophenoxyacetic acid can be included by sorbing the neutral compound in the porous structure of the carrier. Thus, it may be possible to have three or more types of herbicides on the same particle, or have a blend of three or more types on separate particles. The ability to cause death by contaminating only the environment in immediate contact with the plant or animal exhibited by the compositions of the invention makes multiple herbicide treatment practically feasible from the standpoint of cost, capacity of herbicide charge and synergistic activity.

Among the many substantially insoluble copper-con-, taining compounds which have been found useful for purposes , of this invention, the preferred are basic copper (II ) carbonate, copper (II) bicarbonate, copper (l) oxide, copper (II) benzoate, copper (II) hydroxide, copper (II) oxide, copper (I) thiocyanate, copper (l) azide and copper (II) azide. Copper azide is considered explosive, but if kept wet in a slurry, is safe for use. Basic copper (II) carbonate (hereinafter referred to as copper carbonate) is generally preferred as it is easily obtained, inexpensive, and very effective. This material is essentially one hundred percent CuCO^ * Cu(0H)2 with slight traces of other metals and is commonly called malachite „ Where the material is SCuCO^ · Cu(0H)2 it is commonly called azurite and this may also be used.

Although the insoluble character of the copper compounds used In this invention suggests that they would be poor aquatic herbicides, it was found that the insoluble copper-containing compounds effectively controlled many undesirable aquatic plants without having an adverse effect upon fish and other desirable aquatic life when used with the previously described herbicides o The use of relatively insoluble copper compounds has proven to be non-toxic to desirable aquatic life and yet destructive to undesirable plants primarily because of the mechanism by which the c impounds work0 The copper-containing compounds, such as malachite, are in the form of finely divided wettable powders « Compounds not inherently wet -able may be made so by the addition of a V wetting agents such as sodium dioctylsulfosucclnate. Other inert ingredients may also be added to modify the aquatic herbicide, these modi ications being well known in the art.

For example, for certain compounds it may be desirable to include a dust inhibitor, such as glycerine.

When mixed with water, the slurry is sprayed on the surface of the water only in the area of infestation rather than underwater, the procedure recommended for soluble algicides, and, upon solubllizing, permeates the entire area. As the compound settles through the water, it settles on or "clings" to the plant. At this point there is a very slow dissolution of copper ions into the previously copper-free area at the plant surface. As a small amount of copper ion is released, It is absorbed by the plant thus causing additional copper ions to be slowly released. This type of reaction Is best described as the Le Chatelier principle of equilibrium. In accordance with that principle, the absorption of the copper by the plant creates a pressure on one side of the reaction which upsets the solubility equilibrium. Taking the copper ions out of solution by the plant causes the release of more copper ions into that area which in turn are absorbed causing the release of again more copper ions. This controlled release requires that only a small amount of the slightly soluble copper-contai ing compound need be used, especially when used in combination with another herbicide and demonstrates the importance of the copper compound being substantially insoluble. High concentrations of the copper Ion need not be used and, therefore, do not exist in areas other than at the plant surface where the copper is absorbed. As a result, toxic effects on desirable organisms in the surrounding area are r avoided „ The substantially insoluble copper-containing compounds useful in the present invention, as heretofore described, have a solubility in pure water up to about 50 mg. per liter, on the basis of dissolved copper ion0 The preferred solubility range for these compounds is from about 0.001 to l„0 mg. per liter copper ion which is a safe range for desirable aquatic life0- Copper compounds with a solubility greater than 50 mg« per liter will probably dissolve before they reach the plant sought to be destroyed,, An early solubilization of these compounds results in a reduction of release immediately at the plant surface and obviates those advantages described with using insoluble copper compounds having localized activity at the plant surface, such as reduced toxicity to fish, reduced pollution and the use of small amounts „ The compounds should be in a finely divided form so that intimate contact can be made with the undesirable plant and thus increase the efficacy of the absorption of the copper by the plant. For the purposes of the inven ion, the copper compounds are ground to about 0.01 to 1,000 microns (¾-0025 to £.5 cm) in diameter, and 0.1 to 100 microns (.025 to .25 cm) is preferred. Granular material sinks to the bottom and would not be desirable for the purposes of the invention.

The substantially insoluble copper compounds of the present invention have crystalline densities of well in excess of the density of water so that these materials will settle readily therein. The sedimentation characteristics of these compounds were determined by dispersing 5 gnu o the material in 5 gm. of water and pouring the slurry into a 3-3/4 inch (9„5 cm) diameter tube which has a 65-1/2 inch (l66.4 cm) column of water from the surface to the monitoring section, A light source and photomultiplier tube were used to count the particles as they passed the monitoring section. Sedimentation was the greatest in about eight minutes and most of the material settled 20 minutes after application. Results indicate that most of the particles settle on the plant surface in eight to 20 minutes and are not dispersed throughout a large area.

This is important as only the amount of copper that is required to control algae in a given area is needed rather than saturating a whole lake or pond with the material,, Toxicity to desirable species is minimal and cost greatly reduced.

Water solubility of the preferred copper compounds of the present invention was determined by adding them to one-gallon water samples in amounts such that the copper concentration would be five mg. per liter if all the material dissolved.

For example, when testing malachite, the water samples were stirred for four hours and then analyzed for copper. The c opper content in distilled water was 0.007 mg. per liter while in distilled water with the malachite included, it was 0.020 mg. per liter. Similarly the copper content of ordinary lake water was 0.030 parts per million while lake water with malachite had a copper content of 0.090 parts per million. These results indicate that the malachite or basic copper carbonate is substantially insoluble in distilled water or lake water, thus offering a large margin of safety to other marine lifee The synergistically acting compounds may be used in varying amounts depending on the amount of one of the ingredients desired for the specific purpose. Synergistically effective aquatic herbicidal compositions according to the present invention are those containing from about l/2 to 250 parts active organic herbicide for each part active copper-containing compound. Rate of application of the ior- xchange herbicide can be in the range of 1 to 250 pounds ( .45 to 90.7" kg) per acre of active Ingredient and will preferably be used at the rate of 4 to 60 pounds ( 1.8 to 27.2 kg) per acre of active ingredient in controlling undesirable aquatic plants. Rates as high as 110 pounds (50 kg) per acre have been used to control such plants as Hydrllla verticlllata without any injury to desired plants. Active ingredients refer to the herbicidal fraction of the composition.

The copper compound may be used in a range of 1/4 to 400 pounds ( .113 to l8l kg) per acre of active Ingredient, but preferably something less than 10 pounds (4.5 kg) per acre Is used. For algae, 0.025 to 5 parts copper per million parts water may be used in treatment, about 0.05 to 1.0 parts' per million being preferred. For vascular plants, such as Ceratophyllum demersum, from about 0.05 to 20, 0 parts per million may be used. These levels represent total copper.

However, the amount in solution is always much less than the total amount added because of the insoluble nature of the compounds. It is desirable to use as little copper-containing compound as possible because of the toxicity problems previously noted, although toxicity is substantially reduced with such compounds. Localized treatment in accordance with this invention allows broad spectrum control of unwanted aquatic plants with very small concentrations of the two ingredients.

The compounds of this invention are highly effective under a wide variety of aquatic conditions. The material Is effective in water over a wide range of temperatures. It is further effective under widely varying conditions of water clarity, hardness, total alkalinity, pH, and other parameters and is effective at essentially all growth stages of chara filamentous algae, Hydrllla verticlllata, Elode a canadensis, etc. Further, the material is non-corrosive to pumping equipment and mixing tanks and is safer to the applicator than soluble copper-containing compounds.

The invention will be further understood by reference to the following illustrative, but non-limiting Examples, which all parts are by weight unless otherwise noted.

Example 1 Hydrated aluminum chloride, AlCl · 6¾0 in amount of 313 g. (1.3 moles), was dissolved in one liter of water"and the solution was adjusted to pH 5 » 5 with solid sodium hydroxide. The precipitated product was collected by filtration, dried, and then ground to a fine white powder. The material was extracted repeatedly with 500 cc. portions of distilled water, and the amount of Cl~ removed by each extraction was determined by volumetric titration. Extraction was continued until less than 0.1 g/liter of Cl— was present in the filtrate. The elementary analysis values of the residue after 12 extractions were 64.4 percent AlgOg! 9 <, 34 percent CI 0.01 percent Na 0, 01 percent Si, corresponding to the empirical formula AINa (Si02) 0.0004 0.0003 (A12°3 )0o 0i ( 0H )2.78cl0.22 or, ignoring small amounts of impurities, The relative affinity for Al(0H)g_n n of organic acids is in the order dicarboxylic acid^>monocarboxylic acid; disulfonlc aclds^>monosulfonic acids; strongly acid phenols ^ weakly acid phenols.

Samples of this material were exchanged with herbicide anions I through VII from standard aqueous solutions of the toxicant salt. The amount of adsorbed ion was determined by elementary analysis.

A weight of each herbicidal composition thus produced, containing about 0o 00025 ge of adsorbed herbicide, was dispersed into test jars containing 4.5 liters of water in which were growing representative weeds selected from the group of weeds known to be sensitive to the particular herbicide. The particles of the herbicide compositions came to rest on the leaves of the plants. An equivalent weight of each toxicant used was added in its solvated salt form to other weed-containing jars used for controls.

In all cases the plants having herbicide-coated particulate material in contact with foliage were killed within a week, whereas the plants in the control jars continued to thrive indefinitely.

Example 2 Sodium aluminate (100 g.) was dissolved in 3 liters of water. The clear solution (pH 12.5 ) was neutralized slowly with 20 percent aqueous nitric acid. The amount of precipitate increased linearly with each incremental addition of acid. The pH decreased slowly to about pH 10, at which point neutralization was 85 - 90 percent complete. Thereafter, the pH changed relatively rapidly as acid was added, and the mixture was brought to pH 5» 5 » The precipitate which formed was separated by filtration and dried overnight at 120°C. The product was ground to a fine powder and then extracted successively with three 2 liter portions of distilled water. The elementary analysis values (66.3 percent AlP0 j 10.3 percent NO j r Oo04 percent Na) indicated that the material we s essentially Al(0H)2e8(N03)0o2e This material, which can be described as nitrate-containing aluminum hydroxide, adsorbed anions readily as indicated by the ease with which it was stained by anionic dyes but not neutral dyes. Its ion exchange properties were substantially the same as those of the material produced in Example 1.

Other mineral acids, such as hydrochloric, sulfuric, carbonic and phosphoric were used in place of nitric acid to precipitate the aluminum hydroxide „ The amount of anion "X" incorporated in the product Al(0H)3_nXn was a function of the relative affinity and concentration of the anion of the acid at the time of separation.

Similarly, organic acids were used in place of mineral acids with comparable results, e.g. stearic acid, benzoic acid, cinnamic acid, succinic acid, the acid forms of compounds I through V, picric acid and phenol were used to precipitate the aluminum hydroxide by simple neutralization. So long as the final pH value, was above that at which the acid form becomes insoluble, the amount of anion incorporated in the product was about the same as that found using mineral acids. The composition of the products produced is represented by the general empirical formula Al(0H)3_nXn where X is the anion used for neutralization and n ranges from about 0.1 to 2 or higher.

The anions X and OH can be replaced in turn with other organic anions (T) such as those of compounds I through VII as described previously to give a product representable by The herbicide-coated particles produced, e.g. either (l) by direct neutralization of sodium aluminate with the toxicant in acid form or (2 ) by subsequent anion exchange of toxicant for X or OH in Al(OH)^ nXn, were equally effective as aquatic herbicides. The efficacy of toxicant in amounts far smaller than that needed to kill plants when toxicant is used in soluble form, was comparable to that reported in Example 1 using aquatic weeds growing in 4-1/2 liter test jars.

Example 3 Ten parts of sodium aluminate were dissolved in 500 parts of water. Forty parts of pondered hydroblotlte (approximately >200 mesh size) were slurried In a solution for 20 minutes. The mixture was neutralized (pH 7 ) by addition of acetic acid and evaporated to dryness at 70°C. The residue was washed with water and redrled. Analysis showed the organic ion content to be 14.8$, and the ratio of Al to RCOg iff the coating to be 2 , 5: 1.

The Ion exchange characteristics of the adsorbed anion were comparable to those manifested In the absence of inert carrier. The material was found to be stained uniformly with eosln, when eosin-exchanged material was examined with a 60 power microscope, indicating that the coating was firmly bound to the carrier. The eosin dye, in turn, was replaced by other anions by extraction with dilute salt solutions of the anions in question, as described previously. Likewise, the coated hydroblotlte particles absorbed herbicide materials by ion exchange.

Example 4 Sodium Alu-ninate 70$ (9«36 parts) was dissolved in 20 parts deionized water to which 2 .3 parts of 36$ HC1 was added slowly. The mixture was stirred continuously until the initial precipitate had re-dissolved. Powdered hydrobiotite (92.8 parts) was suspended in the solution and the resulting slurry was heated to 809C To this slurry 234 parts of 20$ sodium 2-(2,4,5-trichlorophenoxy) propionate was added and the basic aluminum salt of 2-(2,4,5-trlchlorophenoxy) propionic acid precipitated onto the hydrobiotite carrier. The aqueous slurry was sprayed dried, which is well known in the art, to give a free-flowing powdered product containing 24.30$ of the 2-(2,4,5-trlchlorophenoxy) propionate (commonly referred to as "Silvex") as the active ingredient.

Example 5 P Three separate areas of water, at 72°^. each measuring 375 feet (ll4.3 m) along the shore line by 100 feet (30.5 m) were marked off with stakes in a lake infested with Elodea canadensis. The weed was in the latter stages of vigorous growth. The areas were treated with the aluminum hydroxide salt of endothall as prepared in Example 1 having a carrier as described In Example 3 and substantially water insoluble copper-containing compound separately and together to determine the synergistic effect on the control of plant growth as described in the table below. The materials were mixed in the indicated amount with five times the weight of water in a fiberglass tank equipped with mechanical agitation, and the resulting slurry was sprayed uniformly with mechanical equipment over the area to be treated. In this and the following examples, the dosage rate in lb/A (kg/A) means the number of pounds or kilograms of the indicated material applied per acre.

Similarly, "ppm" means parts per million of the active^ ingredien o Interval Following Tri-al Material Dosage Rate Control Treatment Hydroxy Aluminum salt of endothall on a mica carrier 72 lb/A (13*4$ active ingredient) ( 32.6 kg) 20 12 days copper carbonate 12 lb/A ( 5.4 kg) 0 12 days 3 Hydroxy Aluminum salt of endothall on a mica carrier 72 lb/A ( 13.4$ active ingredient) (32.6 kg) copper carbonate 12 lb/A ( 5. kg) 100 12 days Twelve days after treatment it was noted that copper carbonate alone had no effect and the hydroxy aluminum salt of endothall gave less than 20 control. The two materials used together, however, at the same dosage rates when used alone, gave 100$ control indicating the two compounds acted synergistically to control the plant growth. The background areas had healthy weed growths throughout the ti ial .period.

Example 6 Pour one-quarter acre plots were staked out with buffer zone therebetween, in a large swamp infested with a dense, mature growth of Hydrilla vertlclllata. The water temperature was lQ°F0 (26°C.). The plots were treated as described in Example 5 using the materials and dosage rates listed belows Interval Following Plot Material Dosage Rate Control Treatment Hydroxy aluminum salt of endothall on a mica carrier (13.4$ active ingredient) 1.5 pm 15 15 days 2 basic copper benzoate 1* ppm 0 15 days a Hydroxy aluminum salt of endothall on a mica carrier (13.4$ active ingredient) 1.5 ppm basic copper benzoate 1.5 ppm 35 15 days Fifteen days after treatment, the plot treated with both compounds showed much greater herbicldal activity-fchan would be anticipated from the additive effects of the two materials. The background areas remained essentially unchanged.

Example 7 Three one-acre plots were staked out in a lake infested with mature intermingled growths of Elodes canadensis and watermilfoil (Myrlophyllum exalbescens). The water temperature was 67°F. (210C) o The plots were treated as in Example 4 using the materials and dosage rates listed below; Interval Following Material Dosage Rate Control Treatment Hydroxy aluminum salt of 2- (2,4, 5-trichlorophenoxy)- propionate on a mica carrier 80 lb/A (24.3$ active ingredient) (36.3 kg) 0 28 days 2 basic copper carbonate 7.5 lb/A ( 3.4 kg) 0 28 days 3 Hydroxy aluminum salt of 2- (2, 4, 5-trichlorophenoxy )- propionate on a mica carrier 80 lb/A (24 „ 3 active ingredient) (36.3 kg) copper carbonate 7.5 lb/A ( 3 *4 kg) 50 28 days Again, a synergistic effect on weed control was noted when using the two compounds together. The 0$ control reading applies to both weeds. Plants outside of the treated plots remained unchanged.

Example 8 Three one-acre plots were staked out in a lake infested with vigorously growing coontail (Ceratophyllum demersum) with buffer zones left therebetween. The water temperature was 75°F. (24°C.). The plots were treated as in Example 4 using the following materials and dosage rates: Interval Following Plot Material Dosage Rate $ Control Treatment Hydroxy aluminum salt of endothall on a mica carrier ( 13. $ active ingredient) 1.0 ppm 50 20 days 2 basic copper oxide 0.5 ppm 0 20 days 3 Hydroxy aluminum salt of endothall on a mica carrier (13.4$ active ingredient) 1.0 ppm basic copper oxide 0.5 ppm 90 20 days Twenty days following treatment it was noted that the basic copper oxide alone had no apparent e fect on "the coontail while the hydroxy aluminum salt of endothall gave only 50$ control. The comb nation of the two materials, however, gave 90$ control indicating a synergistic result. The background areas contained dense growths of coontail t hroughout the trial period.

Example 9 Three spaced areas each measuring 200 feet by 200 feet (6l m by 6l m) were staked off in a large shallow bay of a 150-acre lake. The bay was infested with Northern watermilfoil (Myrlophyllum exalbescens) , elodea (Elodea canadensis) , common bladderwort (Utricularia vulgaris), and coontail (Ceratophyllum demersum) . The weeds were all in an active growin stage. The water depth in the treated areas was uniformly in the range 3.4 - 4 feet (1.06 - 1.22 M). The water temperature at the time of treatment was 7 ° F. (23° C.) and the weather was calm and sunny. The materials listed below were mixed with approximately ten times their weight of water and sprayed uniformly over the surface of the plots using mechanical spraying equipment. The dosage rate in lb/A or kg/A means the number of pounds or kilograms of the specified material applied per acre.

Anionic and Copp Dosage Control Herbicide Rate After 25 Weed days Hydroxy aluminum salt of 50 watermilfoil 2-(2,4,5-trichlorophenoxy) 60 elodea propionate (2 .3$ active 20 lb/A 70 bladderwort ingredient) (9 kg) 60 coontail basic copper carbonate 10 lb/A 0 watermilfoil (4.5 kg) 0 elodea 0 bladderwort 0 coontail Hydroxy aluminum salt of 100 watermilfoil 2-(2,4, 5-trichlorophenoxy) 90 elodea propionate (24.3$ active 20 lb/A 95 bladderwort ingredient) (9 kg) 100 coontail basic copper carbonate 10 lb/A (4.5 kg) The results indicate that the two compounds acted synergistically to give 100 control of plant growth while the copper compound alone gave no control. The background areas remained infested. Early in the growing season, six buffered one-acre plots were staked in a bay of brackish water which was infested with Eurasain watermilfoil (Myriophyllum spicatum) . The water was subject to a very slight flow. The water temperature was 6o° P. (1βθ C). The plots were treated by adding the indicated materials to a ten-fold excess of water, and spraying them uniformly over the plots with the aid of mechanical spraying equipment. The water was five feet deep in the plots.

Anionic and Copper Dosage Control after Plot Herbicide Rate 25 days 1 Hydroxy aluminum salt of 2-(2,4, 5-trichlorophenoxy)- propionate on a mica carrier 30 lb/A (23.1 active ingredient) (13.5 kg) 25 2 Hydroxy aluminum salt of 2- (2,4,5-trichlorophenoxy)- propionate on a mica carrier 30 lb/A (23.1$ active ingredient) (13.5 kg) 30 3 basic copper carbonate 10 lb/A (4.5 kg) 0 4 basic copper carbonate 10 lb/A (½. kg) 5 Hydroxy aluminum salt of 2- (2,4,5-trlchlorophenoxy)« propionate on a mica carrier 30 lb/A ( 3.1 active ingredient) (13· kg) 90 basic copper carbonate 10 lb/A (4.5 kg) 6 Hydroxy aluminum salt of 2- (2, 4, 5-trichlorophenox )- propionate on a mica carrier 30 lb/A (23.1$ active ingredient) (13- 5 kg) 98 basic copper carbonate 10 lb/A (4.5 kg) Thirty days after treatment, it was observed that the 2- (2,4, 5-trichlorophenoxy) -propionate anionic herbicide alone gave 25 - 30$ control, and the basic copper carbonate alone gave essentially no control. The two materials together, however, at the same dosage rates, gave almost 100$ control.

The infestation of weeds in the background areas became much more severe during the trial.

Claims (16)

905,48ο What we claim is:

1. In an aquatic herbicide of the type allowing slow release of the herbicidal compound, the improvement characterized in that said herbicide is a synergistically effective aquatic herbicidal composition comprising an effective amount of at least one herbicidal ionic substance bonded by reversible ion exchange to the surface of a water-soluble, particulate, inert carrier whereby the composition, when dispersed in water, is confined to local areas and the said herbicidal substance is desorbed by ion exchange to provide local concentration of the herbicide; and a synergistically effective amount of a substantially insoluble copper-containing compound, whereby said compound settles through the water and rests on the plant so that copper ion is absorbed thereby.

2. The composition of claim 1 further characterized in that the particulate carrier is aluminum hydroxide.

3. The composition of claim 1 further characterized in that said composition is dispersed in water as a slurry.

4. The composition of claim 1 further characterized in that said copper-containing compound is selected from the group consisting of basic copper (II) carbonate, copper (I) oxide, copper (II) oxide,, copper (II) benzoate, copper (II) bicarbonate, copper (II) hydroxide, copper (I) azide and copper (II) azide.

5. The composition of claim 1 further characterized in that said herbicidal ionic substance is the dihydroxy aluminum salt of endothall.

6. The composition of claim 1 further characterized in that said herbicide! ionic substance is the dlhydroxy aluminum salt of 2s -dichlorophenoxyacetate.

7. The composition of claim 1 further characterized in that said herbicidal ionic substance is the dlhydroxy aluminum salt of 2-(2i ,5-trichlorophenoxy) propionate.

8. The synergistically effective aquatic herbicidal composition as recited in claim 1 further characterized in that hydrobiotite is used as the water-insoluble, particulate, inert carrier.

9. The synergistically effective aquatic herbicidal composition as recited in claim 1 further characterized in that said copper-containing compound is basic copper (II) carbonate.

10. A synergistically effective aquatic herbicidal composition as recited in claim 1 further characterized in that said copper-containing compound is basic copper (I) oxide.

11. A synergistically effective aquatic herbicidal composition as recited in claim further characterized in that said copper-containing compound is basic copper (II) hydroxide.

12. A synergistically effective aquatic herbicidal composition as recited in claim 1 further characterized in that said copper-containing compound is basic copper (II) benzoate.

13. A synergistically effective aquatic herbicidal composition as recited in claim 1 further characterized in that said copper-containing compound is basic copper (I) azide. 34979/2

14. The synergis ically effective aquatic herblcidal composition of claim 1, further characterized in that said composition comprises from about 1/2 to 250 parts of active organic herbicide or each part of active copp r-containing compound.

15. In a method for controlling undesirable aquatic plants of the type wherein a slowly released herbicide is applied to the water containing said plants, the improvement characterized by applying to the locus to be protected an herbicidally effective amount of a synergistically effective aquatic herblcidal mixture comprising an effective amount of at least one ionic herblcidal substance bonded by reversible ion exchange to the surface of water-insoluble, particulate, inert carrier and a synergistically effective amount of a substantially insoluble copper-containing compound.

16. The melhodof claim 15,further characterized in that to 60 pounds (1.Θ to 27.2 kg.) herblcidal ionic substance and from one-quarter to ten pounds (0.113 to 4.5 kgl) per acre of active copper-containing compound are used in controlling undesirable aquatic plants.