Green World AN INDUSTRYWIDE PUBLICATION OF THE NEW JERSEY TURFGRASS ASSOCIATION Volume 8, Number 3 Fall 1978 N. J. Research on Insecticide Resistance in Populations Of Japanese Beetles Sami Ahmad, Associate Professor Department of Entomology and Economic Zoology Cook College, Rutgers University, New Brunswick, N.J. Of the many species of soil insects, grubs of the Japanese beetle, Popillia japónica Newman, are the most des­ tructive pest of turfgrass in eastern states. Its current upsurge is attributed to the development of resistance to the cyclodiene insecticides (e.g., chlordane, dieldrin and heptachlor, which in the past afforded good protection against this pest), and the apparent inefficacy of currently used substitute insecti­ cides, diazinon and dursban. Our research on Japanese beetles commenced in the fall of 1977 with the following objectives: 1) to assess the status of cyclodiene resistance in N.J. populations, since thus far it was main­ ly investigated in Connecticut, New York, and Ohio; 2) to screen grubs and adults against currently used insecti­ cides for early detection of insecticide resistance or tolerance that may be indicative of potential resistance, and 3) by a thorough examination of toler­ ance/resistance patterns and addition­ al basic studies concerning the in­ volved physiological mechanisms, to determine the prospects of the long­ term control efficacy of candidate materials for Japanese beetle control. Sensitive Technique Our initial research was concerned with the development of a sensitive laboratory bioassay technique for Japanese beetle grubs. A topical meth­ od of insecticide application by which precisely measured amounts of insecti­ cide could be administered to the cuti­ cle of each grub was developed. A rearing medium to maintain grubs for the duration of the bioassay was also developed, and the symptoms of insec­ ticide poisoning in the grubs were discerned (Fig. 1). (Page 3, please) Liquid Fertilizer Use Demands Basic Knowledge R.N. Carrow Until recent years most of the ferti­ lizers used in turfgrass management were in the granular formulation. However, liquid and powdered mater­ ials are now widely promoted and utilized. Each formulation offers uni­ que advantages under certain circum­ stances but may not be the best mater­ ial under other conditions. If a turf manager is to select the proper formu­ lation he should understand the pros and cons of each type. The discussion in this article will be mainly on nitro­ gen since this is the major nutrient most often applied. GRANULAR FORMULATIONS Many different types of nitrogen carriers are available in the granular form. Table 1 lists common granular nitrogen carriers and their characteris­ tics. In addition to these carriers many mixed fertilizers are available which contain two or more different carriers mixed together. For example, a mixed fertilizer may contain 50 percent of its nitrogen from ammonium nitrate and the remainder from UF. Turfgrass response to a particular granular fertilizer depends upon its characteristics, such as slow release, fast release, long residual, short resi­ dual, etc. Dr. Carrow is assistant profes­ sor of ornamental horticulture and turf at Kansas State University. We are pleased to publish this much-appreciated paper that he gave at the 16th Annual Nebraska Turfgrass Conference this year. The complete transcript contin­ ues on Page 4. Figure 1 a) A normal third-stage grub of Japanese beetle. b) Insecticide-poisoned SYM stage. SYM = shrinking (S) of body and reduction of body weight to about one-half of a healthy third-stage grub, yellow-brown (Y) coloration of the body, and moribundity (M). Once the insecticide-treated grubs manifest these three symptoms, they are certain to die. c) An insecticide-treated deceased grub. Dead grubs are usually darker than the SYM grubs, and within a few hours bloat by the decomposition of the body. Comments and Opinions. BLACK MONDAY! Monday, August 14, 1978, was a black day for fairway turf on a number of courses. It seemed that the annual bluegrass and some bentgrass wilted faster than six watering systems could have syringed. Two things seem to associate with the trouble. Curvularia organism was abundant on several of these sites. I noted this association in two previous summers where abrupt wilt developed. Second, most of these damaged areas had higher nitrogen or spring fertilization. This was not a consistent association. The N. J. Superintendents played a course that had received appreciable nitrogen this season and it had excellent turf on August 17. Another superintendent reported the same exper­ ience. happened or did not happen on August 14. I feel convinced that the fungicide program was a big factor in what — R.E.E. GLYPHOSATE - SOMETHING NEW Glyphosate sold as “Roundup” by Monsanto Chemical Co., one of the few new chemicals, that has shown us that one application will give kill economically of both turf and weeds. Kill develops slowly over 10 days to two weeks but reseeding can follow the herbicide within seven days without harm. Read the label for specific directions on timing and rate. It is easy to imagine many interesting uses for this type chemical. As with all new chemicals, starting with small scale projects is best until you are sure how everything works. Since the chemical has no preemerge effect on germinating seeds, remember that killing the turf without reseeding or using a preemerge herbicide will give a crop of weeds. Also, use of this chemical where soil is erodible because of slope, intense water flow or other causes may lead to a problem of soil erosion bigger than the weed problem. We must remember that a poor or weedy turf may be giving more erosion control than we appreciate. We would be pleased to have your comments on use of this new chemical, — R.E.E. and John A. Meade glyphosate. _ . Are you reading us? If you are, we would be glad to have your comments. Both turf wisdom and humor are accept­ ed. OFFICERS OF THE N.J.T.A. Chuck Wilson President Jack Wittpenn Vice President Ralph Engel Secretary and Consulting Editor William Ritchie Treasurer A tramp was sleeping behind the bunker of a golf course when the club secretary, prowling around, kicked him none too gently and ordered him to clear out. “And who are you?” demanded the —Family Weekly tramp haughtily. “I’m secretary of the club,” replied the official curtly. “Well,” snorted the tramp, who knew how to save face, “That’s no way to get new members.” Green World is published three times a year by the New Jersey Turfgrass Asso­ ciation, P.O. Box 231, New Brunswick, N.J. 08903. Ralph Engel, consulting editor; Russell Stanton, managing edi­ tor. Please address inquiries concern­ ing advertising to Jack Wittpenn, ad­ vertising director, Box 809, W. Cald­ well, N.J. 07006 (575-1322) EXECUTIVE BOARD Dave Buchholz Fred Eden Edgar Krause Samuel Leon Paul Sartoretto Ken Kubik Paul Boizelle Past President (BEETLES from Page 1) Following the development of this bioassay procedure, we tested the third-stage grubs of Japanese beetle from Edgewood Country Club golf course in Rivervale, N.J. Results of this investigation showed that these grubs were most likely resistant to the cyclodiene insecticide, dieldrin. Also, it appeared that the Rivervale popula­ tion of grubs was quite heterogenous in its response to the organophosphate insecticide, dursban. Current Findings Confirm systematic survey of resistance/toler- ance patterns involving several popula­ tions of Japanese beetle throughout the eastern U.S. to determine whether the Rivervale situation is an isolated case, or is in fact widespread. Also, insecticide screening should be conducted every year on some selected populations, to see if the tolerance level is on the rise, and if so to what extent. Besides these early-warning studies, we ought to initiate investigations of other pest management options. This will require a good knowledge of popu­ lation dynamics, and the development of a good sampling technique for predicting Japanese beetle population with accuracy. Research is also needed in the area of micropathogens, i.e., milky spore disease that is reportedly becoming ineffective, parasites and predators and other biotic factors that may be useful in the integrated control of this pest. Recently, the sex-pheromone (chemi­ cal given out by females to attract males for mating) for this species has been isolated. This substance may be exploited as an effective lure for trap­ ping male beetles soon after adult emergence, thereby preventing mating and subsequent egg-laying. Finally, a possibility exists for deve­ loping some of the new experimental insect growth inhibitors such as dimilin and EL -494 and related materials for grub control. Further studies this summer with adult Japanese beetles from Rivervale and another population from Adelphia (Soils and Crops Research Center, Rutgers Agric. Exp. Stn.), confirmed the findings of our fall, 1977 study. These data show conclusively that the Rivervale population, by comparison to the one from Adelphia (which has not been treated with any insecticide during the past several years), is highly resistant to dieldrin. Furthermore, when the Rivervale population was compared to the Adel­ phia population, a three- to four-fold greater tolerance to both dursban and bendiocarb, a potential carbamate in­ secticide for turfgrass beetle control, was found. This greater tolerance of the Rivervale population is apparently due to the presence of a greater numb­ er of individuals inherently tolerant to insecticides. This kind of variability in insecticide response often leads to the selection of tolerant insects under con­ tinuous insecticide pressure, and ulti­ mately to the development of a resis­ tant strain. Therefore, a possibility exists that with time, the Rivervale population may become resistant to organophos­ phates and carbamates, in addition to cyclodienes. However, unlike cyclodiene resistance which is of least concern because EPA has restricted its use due to environmental hazards, the possibility or organophosphate and carbamate insecticide resistance is alarming. Unfortunately, classes of in­ secticide other than the aforemen­ tioned, do not exist at the present for turfgrass beetle control. Further Research Needs So what are the options in the face of the potential threat of organophos­ phate and carbamate insecticide resis­ tance? First, we must initiate a USS Vertagreen Fall Fairway Fertilizer We’ll help winterize your fairways! Hit the fairways this fall with an application of this great new USS Vertagreen fertilizer and you’re on your way to fewer turf problems next spring. This quality product is ideal for fall fairway fertilization because it has a high potash analysis ... and that means less winter kill. or early fall will determine if A soil test in the late summer your fairways lack this vital nutrient. If they do, USS Verta­ green Fall Fairway Fertilizer is the answer because it's formulated with primary nutri­ ents specifically for your area. See your USS Vertagreen distributor and he’ll show you how to winterize your fairways this fall. Next spring you’ll be glad you did. Agri-Chemicals Division of United States Steel PO Box 1685. Atlanta, Ga. 30301 (FERTILIZER from Page 1) Careful selection of a solid fertilizer can allow nitrogen availability to close­ ly match the plants’ needs. In spring and fall a higher proportion of nitro­ gen could be of the fast-release type for cool season turf, while slow-release forms are appropriate for summer. The ability to release nitrogen over an extended period is an advantage for many granular products. On large acreages of turf, solid ferti­ lizers are the easiest to apply. However, on small sites such as home lawns, golf greens and tees, liquid or powdered formulations may be faster and easier to apply. Granular materials have some dis­ advantages if not used properly. Physiological drought, leaching, and excessive stimulation of growth can occur if water-soluble materials are applied at too high rates. Volatilization and foliar burn are likely to result if water-soluble forms are not adequate­ ly watered into the soil. On close-cut turfs, mowers can pick up coarse granules. LIQUID FORMULATIONS In granular materials the nutrient carrier is a solid, while in liquid ferti­ lizers the carrier is water. Since the nutrients are dissolved in water, ab­ sorption can occur immediately upon contact with leaf surfaces or roots. Most liquid fertilizers are combina­ tions of salt fertilizers (Table 2). Many different analyses can be produced by various combinations. In addition to the three major nutrients (N,P, K), other ingredients may be claimed such as calcium, magnesium, iron, manganese, boron, copper, zinc, molybdenum, sulfur, vitamins, wetting agents, growth stimulants, and chlor­ ophyll. Liquid fertilizers can be ap­ plied by soil drench or foliar feeding. Soil drench involves application of nutrients in sufficient water (25 gal. per 1000 ft.) that a majority of the nutrients are washed into the soil. Absorption of the nutrients by the plant is predominantly through the root system. Soil drench fertilization is commonly utilized by the home lawn care industry, for small sites such as golf greens and tees and for large acreage by “fertigation.” Advantages of Applying Liquid Ferti­ lizers As a Soil Drench: • Ease and efficiency of application. On small sites a soil drench can be applied quickly and uniformly with a sprayer or a hand hose connected to a spray tank. Appli­ cation time can be reduced by about one half compared to gran­ ular application. • Other chemicals can often be mixed into the tank and thereby further reduce applicaton time. • Nutrients are readily available to the plant. However, some nutrients such as phosphorus and iron can be quickly absorbed by the soil colloids and become una­ vailable. Nitrogen is readily avai­ lable and well-timed soil drench can supplement your normal ferti­ lization program. Precautions and Disadvantages of a Soil Drench: • Large volumes of water are WE’VE GOT WHAT YOU NEED FERTILIZERS. I.B.D.U. Ureaform GRASS SEEDS: Bulk or Custom Mixes INSECTICIDES: Diazinon, Dursban, Etc. FUNGICIDES: Cleary’s, Daconil WEED KILLERS: Balan, Betasan, Dacthal The TERRE Co Saddle Brook, N.J. (201) 843-6655 Table 1. Common nitrogen carriers available in the granular form and their characteristics. N carrier Synthetic inorganic (salts) Ammonium nitrate Ammonium sulfate Calcium nitrate Sodium nitrate Natural organics: Activated sewage sludge Bone meal Cottonseed meal Fish scraps Characteristics Water soluble Rapid initial plant response Short residual (2-4 weeks) Subject to leaching High foliar burn potential Not water soluble Depends on microbial activity for N release; soil temperatures greater than 55 °F Low leaching potential Low foliar bum potential Medium-long residual (4-8 weeks) Table 2. Compounds used to formulate liquid fertilizers. Compound Analysis Ammonium nitrate Ammonium sulfate Calcium nitrate Calcium sulfate Diammonium phosphate Monoammonium phosphate Monoammonium phosphate, commercial grade Potassium nitrate Potassium chloride Potassium sulfate Potassium phosphate Potassium phosphate Sodium nitrate Urea 33-0-0 20-0-0 15-0-0 (40% Ca) 0-0-0 (30% Ca, 70% SO4) 21-53-0 12-61-0 11-48-0 13-0-44 0-0-60 0-0-48 0-52-35 0-41-54 16-0-0 45-0-0 required. For large areas a soil drench can require much more time per appli­ cation due to the necessity of refilling the spray tank. If less than 25 gallons of water per 1000 sq. ft. is used then nitrogen should be restricted to 0.5 lb. nitrogen or less per application. Appli­ cations of over 1.5 lb. N/1000 sq. ft. should not be attempted, even with large quantities of water. • Since the nutrients are water- soluble salts, they have all the disadvantages of water-soluble granular materials. Leaching can occur from excessive irrigation or precipitation. Foliar burn may result if too little water is applied. It is a good practice to irrigate after a soil drench. Nitrogen resi­ dual is normally only two to four weeks. If higher rates of nitrogen are used excessive stimulation of the turf can occur. • Excessive thatch can inhibit nutrient penetration. This is espe­ cially a problem during hot, dry periods where salts may accumu­ late in the drench layer and cause salt injury. • Liquid fertilizers generally have a marked effect on soil pH. Some materials increase pH but most reduce pH, especially urea and ammonia forms of nitrogen. Check the pH periodically and apply limestone if necessary. • If a complete (has N-P-K) liquid fertilizer is consistently used, phosphorus and potassium levels may become excessive. This could result in Poa annua or clover en­ croachment. Also, liquid fertilizers containing micronutrients should not be applied unless a specific deficiency is evident. • Frequent, light fertilization is often necessary with a soil drench since soluble fertilizers have a short residual. In midsummer crabgrass, foxtail, and goosegrass may respond more to such frequent, light fertilization than will cool- season grasses. • Care should be taken not to over­ stimulate the turf by too frequent fertilizations. A soft succulent turf will result which will be less toler­ ant to heat, cold, drought, wear, and disease stresses. • Spray drift has often been a prob­ lem with soil drench applications. However, careful selection of noz­ zles and good technique will eli­ minate this potential problem. Foliar Feeding Foliar feeding is the application of small amounts of nutrients in a limited volume of water (0.5 gal per 1000 sq. ft.) so that nutrients are absorbed through the shoot tissues. Foliar feed­ ing has not been extensively used in turfgrass culture. However, iron, mag­ nesium, manganese, and small quanti­ ties of nitrogen can be effectively ap­ plied in this manner. Also, fertigation systems can be utilized for foliar feed­ ing. The major advantage of foliar fertili­ zation is that certain nutrients (N, Fe, Mg, Mn) can be quickly absorbed through the leaves and result in rapid color and growth responses. When con­ ditions restrict root uptake (water­ logged soils, compaction, nutrient fixa­ tion by soils), foliar feeding will correct nutrient deficiencies, while soil appli­ cations would be of little benefit. A second advantage of foliar feeding is that it can often be incorporated with pesticide applications. No more than 0.5 gal of water per 1000 sq. ft. should be used and care should be taken to insure compatibility of chemicals. A third advantage is that nutrient leaching losses are greatly reduced since only small quantities are applied at any one time. Disadvantage of Foliar Nutrient Ap­ plications: • Only small quantities of nutrients can be safely applied at any one time. For example, nitrogen is generally applied at 0.05-0.125 lb. per 1000 sq. ft. High rates could easily result in foliar burn for salts or phytotoxic levels for micronu­ trients. • Repeated, frequent applications are necessary to provide an ample nutrient supply. Generally appli­ cations every one or two weeks are required. • Since the leaf tissues are the ab­ sorption sites, nutrient uptake will be adversely affected by anything which reduces leaf area or physio­ logical health of the leaves. Close- cut turfs and turf exhibiting (Page 6, please) Garfield Williamson WHOLESALERS & DISTRIBUTORS Products for the Professional BULK SIZES/SPECIAL MIXES NEWEST VARIETIES Grass Seed Fertilizers Chemicals Featuring: FINE LEAF PERENNIAL RYE GRASS Garfield Williamson, Inc. 1072 West Side Avenue. Jersey City. N.J 07306 201-435-3500 curred on more than one occasion in New Jersey. Drs. Spencer Davis and Philip Halisky have isolated Rhizocton­ ia from these. Also, the organism was isolated from one sample collected in Southern New Jersey. The infected areas are similar to those found in Arkansas. The injured turf has the same bleached appearance with partial kill of the zoysia plants in the circle. The circles have a well- defined edge and they persist for months. The injury occurring in New Jersey differs in size of the circles which frequently range up to 8 pr 12 feet in diameter. — R.E.E. and S. H. Davis ABSTRACT Atypical Symptoms of Rhizoctonia In­ fection on Zoysia, J. L. Dale. Plant Disease Reporter. 62: 645-647, 1978. In the fall of 1976 and 1977 unusual disease symptoms resembling Fusar­ ium blight disease were observed on zoysia in northwest Arkansas. In both years, however, Rhizoctonia sp. was isolated from the infected turf. In cul­ ture the Rhizoctonia grew faster at 24° than at 28° C. Average growth rate of cultures on potato-dextrose agar at 24° C was 9.1 mm. per day. Hyphal cell diameter averaged 4.5 /¿m. Stained mycelium indicated that hyphal cells were consistently binucleate. Attempts to produce the perfect state were not successful. Consistent binucleate con­ dition of hyphal cells and other charac­ teristics of the fungus, however, suggest that the Rhizoctonia involved is of the Ceratobasidium group rather than being R. solani, which is normally associated with diseased turf. COMMENTS: When zoysia was first introduced for turf in Northeast United States, some statements said it was a disease-free grass. Its tough leaf tissue would ap­ pear to resist any disease. Sadly, like all things biological this grass has a few problems. The above abstract showing Rhizoc­ tonia on zoysia is of special interest because disease-like rings have oc­ Zoysia turf showing atypical bleached spots and “frog-eye” symptoms produced by Rhizoctonia sp. in autumn 1977. Ruler in photograph is 0.3 m. in length. Hyphae of Rhizoctonia sp. isolate from zoysia showing binucleate condition after Giemsa staining of mycelium. (FERTILIZER from Page 5) nutrient deficiencies are less effec­ tive nutrient absorbers than high- cut, healthy grasses. In many situations a spreader or sticker aids in good coverage of the leaf. • Once on the leaves, nutrients enter the plant through stomata and to some extent through the cuticle. For maximum uptake the leaf environment must be moist and the stomata open. Hot tempera­ tures and low humidity can decrease uptake by inducing stomatal closure and drying out the leaf surfaces before uptake can occur. Such conditions also promote volatilization losses of nutrients. • Nutrients are not absorbed at the same rate by leaf tissues. For example, nitrogen is absorbed much more rapidly than phos­ phorus which can result in nutrient imbalances. Fertigation Fertigation is the application of nutrients through an irrigation system. Fertigation can be used to apply nutrients as either soil drench or a foliar feeding. Whichever method is SUSTAINING MEMBERS (As of August 1978) A-L Services Andrew Wilson, Inc. Lewis W. Barton Co. W. A. Cleary Corporation The Country Greenery, Inc. Kelly DeFreitas & Assoc. Double Eagle Golf and Industrial Sales Garfield Williamson, Inc. Green Hill Turf Supply Harvest Publishing Co. Hummer Turfgrass Systems Lawn-A Mat - Mountainside Leon’s Sod Farm Limestone Products Corporation Lofts Pedigreed Seed, Inc. Mercer Sod, Inc. Metro Milorganite, Inc. Pine Island Turf Nursery Playboy Resort & Country Club Rockland Chemical Co. Seacoast Laboratories Storr Tractor Co. Techniturf, Inc. The Terre Company Vaughan-Jacklin Corp. Wide Sky Farm, Inc. used will have all the advantages and disadvantages that were previously dis­ cussed. However, it has some addition­ al pros and cons which are worthy of discussion. The primary advantage of fertiga- tion is in labor saving. Large areas can be fertilized with little additional labor beyond that needed for normal irriga­ tion. The major problem encountered with fertigation is poor distribution. The uniformity of fertilizer distribution will be no better than the uniformity of irrigation. Overlaps and misses in the irrigation system will be accentuated with fertigation. In the Central Plains high winds often distort irrigation pat­ terns. Distribution patterns can be eva­ luated by placing cans at various dis- Can’t Beat Dandelions? Then Eat ’em (Or Drink ’em) As a lawn care businessman, you may spend certain times of the year doing nothing but worrying about get­ ting rid of your customers’ dandelions, but in Vineland, N.J., the first harvest of the lowly yellow weed is a cause for celebration. “If you can’t beat ’em, eat ’em — and if you can’t can’t eat ’em, drink ’em,” said Mayor Patrick Fiorilli. More than 400 townsfolk in the rural south Jersey town paid homage to the dandelions with unabashed fanfare. They jammed a grammar school gymnasium at $12 each to feast on crisp dandelion salad, murky dande­ lion soup, fresh dandelion ravioli, tender veal tips with dandelion, dande­ lion gelatin and dandelion wine — lots of dandelion wine. Dandelions are a serious spring crop in the area, where 16 farmers plant the weed’s seeds in August and harvest dandelions as the ground thaws in March. Dandelions for salad greens are worth $40,000 a year to local farmers. — Lawn Care Industry tances from each head and noting the quantity of water per can. If an area consistently receives twice as much water compared to another site, then it will also receive twice as many nutri­ ents with fertigation. Irrigation systems that are not flexi­ ble present problems with proper ferti­ lization. Roughs, fairways, tees, aprons, approaches and greens may all require different fertilization regimens. With fertigation this can only be done if the system has much flexibility. Other drawbacks of fertigation systems include corrosion of equip­ ment and fertilizer precipitation. These can be corrected with proper equip­ ment and maintenance. POWDERED FORMULATIONS Features KENTUCKY BLUEGRASSES: TURF TYPE PERENNIAL RYEGRASSES: ( 3 bluegrasses perfectly blended) Pedigreed Seed, Inc. • Baron* • Touchdown • Majestic • Tri-Plex Blue • Yorktown" • Yorktown II • Diplomat • Tri-Plex Rye • Jamestown • and Custom Blends (3 ryegrasses perfectly blended) Chewings Fescue Write or call for further information and current price* LOFTS Lofts Pediareed Seed. Inc. Bound Brook. NJ OttOS / (201) 35«*l700 "US Plant Patent #3186. Dwarf Variety ' "Protection applied for under the US Plant Variety Protection Act burn, does not leach, and has a longer residual than water-soluble carriers, whether applied as a granular or liquid material. Very little research data is available on powdered UF. However, much research has been conducted on granular UF. Since the powdered UF has a much greater surface area, it would not be expected to have as long a soil residual as granular UF. Thus, turf response to the granular and pow­ dered formulations may not be identi­ cal. Normally powdered UF is applied at 1 to 2 lb. N in 5 gal. H2O/IOOO ft. At this rate of water application, clip­ pings must be returned since apprecia­ ble nitrogen will collect on leaves, especially in hot, dry weather. There is no one ideal fertilizer for all turfgrasses and situations. One consi­ deration when selecting a fertilizer is the correct physical formulation. This requires knowledge of the growth pat­ tern of the grass, equipment and labor capabilities, and a basic understanding of the characteristics of each type of fertilizer carrier. In recent years ureaformaldehyde (UF) has been available in a powdered formulation which can be applied through a spray system. The lawn care industry has been very much interested in this material since it has low foliar Our forefathers went out and built empires; today you must have a permit to add a room to your home. — Hudson Valley Foreground ABSTRACT Influence of the Chemical Form of Mercury on Its Adsorption and Ability to Leach Through Soils, by T. J. Hogg, J. B. W. Stewart and J. R. Bettany. J. Environ. Quality 7: 440-445. 1978. The adsorption of Hg by two soils, differing in chemical and physical characteristics, indicated that both or­ ganic Hg compounds (methyl mercuric chloride [MMC] and phenyl mercuric acetate [PMA]) and inorganic com­ pounds (mercuric chloride [HgCh]) followed the linear form of the Lang­ muir adsorption isotherm. The highest adsorption maxima for all Hg com­ pounds were found for the soils which had the higher organic matter content and clay content. Adsorption maxima increased in the order MMC