Methyl Phosphorodithioate Research Articles

Effects of dimethoate ( O, O-dimethyl S-methyl carbamoyl methyl phosphorodithioate) and Ethanol in antioxidant status of liver and kidney of experimental mice

Organophosphorus insecticides and ethanol individually cause free radical production induced by oxidative stress and alter the antioxidants and scavengers of free radicals. The present study indicates the effect caused by dimethoate in combination with ethanol on antioxidant status in mice. Daily, dimethoate at a dose of 18 mg/kg body weight and ethanol at 1 g/kg body weight were orally administered concurrently in a subacute study for 14 days. After the experimental period, the liver and kidney homogenates were analysed for various antioxidant enzymes. The results compared with dimethoate alone treated control indicated an increase in hepatic cytochrome P450 and lipid peroxidation. Decrease in superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione- S-transferase, and glutathione in liver was observed. In kidney, decrease in CAT, SOD, GR, GST, and GSH was observed. Acetyl cholinesterase activity of RBC was increased. No significant change was observed in catalase in liver and glutathione peroxidase in kidney. The results of the study allow us to hypothesize that dimethoate along with ethanol disturbs the antioxidant status.

Effect of Tillage System, Phorate, and Cultivar on Tomato Spotted Wilt of Peanut

Tomato spotted wilt (TSW) has become a limiting factor to peanut (Arachis hypogaea L.) production in the southeast United States over the past 6 yr. Cultivars are now selected based on their resistance to TSW and planted during time periods to reduce the incidence of TSW. Three peanut cultivars with different resistance to TSW were used (‘Georgia Green’, ‘MDR98’ and ‘SunOleic 97R’). Conventional‐ or strip‐tilled plots were established after winter wheat (Triticum aestivum L.) in 2000 and 2001 in Marianna, FL. Stand count, severity of TSW, and yield were recorded. Plots were irrigated as needed. Stand count was 10% less in the strip‐tilled plots in both 2000 and 2001. Stand count was affected by cultivar used, with Georgia Green and SunOleic 97R having 20% higher populations than MDR98. Phorate [O, O‐diethyl,S‐(ethylthio)methyl phosphorodithioate] treatment had 7% less stand count in 2001 but not in 2000. Tomato spotted wilt severity was 50% less in strip‐tilled plots in 2000, but there was no difference in 2001. Cultivar affected severity of TSW every year but not consistently. Application of phorate did not affect TSW. In 2000 (a droughty year), the strip‐tilled plots had greater yield (2510 vs. 1900 kg ha−1) averaged across cultivars. MDR98 had the highest yield across treatments in 2000, but yield was not different among cultivars in 2001. Application of phorate did not affect yield in either year. In the strip‐tilled plots, soil moisture was 30% greater and plant canopy 3 to 5°C cooler during 2000 when plants were visibly drought stressed. Use of phorate had no effect on TSW or yield and its use for TSW control is not recommended. Cultivar selection did influence TSW severity and should be considered as part of a TSW control program. Strip tillage resulted in greater yields than conventional tillage in an abnormally dry year.

Effect of Tillage System, Phorate, and Cultivar on Tomato Spotted Wilt of Peanut

Tomato spotted wilt (TSW) has become a limiting factor to peanut (Arachis hypogaea L.) production in the southeast United States over the past 6 yr. Cultivars are now selected based on their resistance to TSW and planted during time periods to reduce the incidence of TSW. Three peanut cultivars with different resistance to TSW were used (‘Georgia Green’, ‘MDR98’ and ‘SunOleic 97R’). Conventional- or strip-tilled plots were established after winter wheat (Triticum aestivum L.) in 2000 and 2001 in Marianna, FL. Stand count, severity of TSW, and yield were recorded. Plots were irrigated as needed. Stand count was 10% less in the strip-tilled plots in both 2000 and 2001. Stand count was affected by cultivar used, with Georgia Green and SunOleic 97R having 20% higher populations than MDR98. Phorate [O, O-diethyl,S-(ethylthio)methyl phosphorodithioate] treatment had 7% less stand count in 2001 but not in 2000. Tomato spotted wilt severity was 50% less in strip-tilled plots in 2000, but there was no difference in 2001. Cultivar affected severity of TSW every year but not consistently. Application of phorate did not affect TSW. In 2000 (a droughty year), the strip-tilled plots had greater yield (2510 vs. 1900 kg ha−1) averaged across cultivars. MDR98 had the highest yield across treatments in 2000, but yield was not different among cultivars in 2001. Application of phorate did not affect yield in either year. In the strip-tilled plots, soil moisture was 30% greater and plant canopy 3 to 5°C cooler during 2000 when plants were visibly drought stressed. Use of phorate had no effect on TSW or yield and its use for TSW control is not recommended. Cultivar selection did influence TSW severity and should be considered as part of a TSW control program. Strip tillage resulted in greater yields than conventional tillage in an abnormally dry year.

Artifact formation in the GC/MS analysis of Zolone EC (phosalone) insecticide formulation

In an investigation of potential causes for three grape-harvester pesticide poisoning incidents, acetone extracts of Zolone EC [active ingredient, phosalone [O,O-diethyl S-(6-chloro-2-oxobenzoxazolin-3-yl)-methyl phosphorodithioate]] were analyzed by GC/MS for the presence of possible impurities. Initial findings suggested the presence of isophosalone [O,S-diethyl S-(6-chloro-2-oxobenzoxazolin-3-yl)methyl phosphorodithioate], a phosalone isomer containing S-ethyl and oxon functionalities, as a formulation impurity. High-resolution and tandem mass spectrometry experiments confirmed the structure of isophosalone. An additional solid probe tandem mass spectrometry study and investigations of the effects of injector temperature, column length, and on-column injection verified that isophosalone was produced as an artifact of gas chromatography and was not initially present in the Zolone EC formulation. The results demonstrate the utility of high-resolution and tandem mass spectrometry experiments for structural confirmation and illustrate that the potential exists for formation of isomer artifacts of phosphorodithioate insecticides during the gas chromatographic process.

A tissue culture derived pesticide tolerant line of chickpea (Cicer arietinum L.)

Chickpea seedlings (Cicer arietinum L.) were used to initiate callus on B5 medium supplemented with 2 mg/l 2,4-dichlorophenoxyacetic acid+0·5 mg/l NAA and kinetin. After a month's growth the healthy callus was transferred to a similar medium supplemented with different concentrations of the pesticide Rogor (O, O-dimethyl-S-methyl carbamoyl methyl phosphorodithioate). After one month in the pesticide medium most of the cells exposed to higher concentration died, but a few cells remained healthy. In a control medium the cells remained healthy over the same period. The pesticide treatment inhibited the protein content and the activity of the enzyme amylase, whereas an increase in the activity of peroxidase was observed. The surviving pockets of pesticide exposed cells were exercised and transferred to a medium that caused shoot initiation and later to a medium that caused root formation from the base of the shoot. Plants were taken through to maturity in soil. The resistant cell line contained high levels of proteins and peroxidases compared to control. Additional bands of peroxidase isozymes were observed in the resistant line.

Phosalone applied to cotton (Gossypium hirsutum L.): its deposition and persistence on foliages, soils and final residues in seeds.

Phosalone, O,O-diethyl-S-(6-chloro-1,3-benzoxazol-2(3H)-onyl)methyl phosphorodithioate, was field-applied by ground equipment to cotton (Gossypium hirsutum L.) at the rates of 1050 and 2100 g a.i./ha, respectively, to determine its dissipation on leaves and soils and the residues in seeds at harvest. The insecticide concentrations on cotton leaves and soils were measured periodically for 14 days following its application. It was found that the half lives of the insecticide on cotton leaves at the dosages of 1050 and 2100 g a.i./ha were 6.8 and 6.3 days, respectively. And the half lives on soils for the 2 dosages were 7 and 5.8 days, respectively. The residues remaining in soils at harvest time were 0.072 and 0.121 mg/kg 14 days post-application and the residues in cotton seeds were relatively low (less than 0.02-0.12 mg/kg).

Phorate and mexacarbate induced changes in enzymes of the snail,Lymnaea acuminata

The snailLymnaea acuminata, vector of the liver flukesFasciola hepatica andFasciola gigantica, was exposed to 40% and 80% LC50 doses of the pesticides 12/24 mg/L phorate (O,O-diethylS-(ethylthio) methyl phosphorodithioate) and 2.5/5.0 mg/L of mexacarbate (4-dimethylamino)-3,5-dimethylphenyl methyl carbamate) for 24 or 48 hr. These pesticides, although considered to be antiacetylcholinesterase agents, inhibited alkaline phosphatase and enhanced the activity of acid phosphatase in hepatopancreas, mantle, intestine, and foot of the snail. Trypsin activity in the alimentary canal of the snail was also inhibited. Discontinuation of pesticide treatment resulted in partial recovery in mexacarbate-treated animals while in phorate-treated animals the effect of the pesticide was largely irreversible.

Relative toxicities of phorate and some of its metabolites to Aphis fubae Scop

AbstractAn aqueous solution of bromine was used to oxidise 14C‐labelled phorate to its metabolites. A substantial amount of [14C]phorate sulphone (O,O‐diethyl S‐ethylsulphonyl[14C]methyl phosphorodithioate) with minute quantities of [14C]phorate sulphoxide (O,O‐diethyl S‐ethylsulphinyl[14C]methyl phosphorodithioate) and [14C]phoratoxon sulphoxide (O,O‐diethyl S‐ethylsulphinyl[14C]methyl phosphorothioate) were recovered using this method. Various concentrations of [14C]phorate and these toxic metabolites were individually incorporated in an artificial diet and fed to Aphis fabae Scop. Mortality was recorded after 48 h. The toxic fractions of the compounds were extracted from the diet and their radioactivity was measured to determine the dose unit. The aphids feeding on diet containing high concentrations of [14C]phorate sulphoxide and [14C]phoratoxon sulphoxide were seen wandering restlessly, which suggested that the acceptability of the diet had been changed by the presence of these metabolites. Phorate appeared to be the most toxic to the aphids, followed by phorate sulphone, phorate sulphoxide and phoratoxon sulphoxide in that order; the reasons for this are discussed.

Crystal and molecular structure of organophosphorus insecticides. 3. Azinphos-methyl

The crystal and molecular structure of azinphos-methyl (O,O-dimethyl S-(4-oxo-1,2,3-benzotriazin-3-yl)methyl phosphorodithioate), C/sub 10/H/sub 12/N/sub 3/O/sub 3/PS/sub 2/, has been determined by three-dimensional x-ray analysis. The compound crystallizes in the monoclinic space group P2/sub 1//c with a = 12.084 +- 0.007, b = 15.190 +- 0.008, c = 7.856 +- 0.003 A, and ..beta.. = 98.39 +- 0.03/sup 0/ with Z = 4. Graphite-monochromated Mo K..cap alpha.. radiation (lambda = 0.70954 A) was used for measurement of diffraction data at 10/sup 0/C. The structure was solved via direct methods and refined by a full-matrix least-squares procedure to a final discrepancy index of R = 0.080. The phosphorus-(carbonyl carbon) distance corresponding to the anionic-esteratic site separation of acetylcholinesterase is 4.83 (2) A for azinphos-methyl in the solid state. No appreciable intramolecular interactions which might limit the accommodation of a large range of anionic-esteratic separations were observed.

THE TOXICITY OF INSECTICIDES BY CONTACT AND SOIL TREATMENT TO TWO SPECIES OF GROUND BEETLES (COLEOPTERA: CARABIDAE)

AbstractAdults of predatory carabid beetles (Coleoptera: Carabidae) of the species Stenolophus comma Fabricius field-collected from light traps were bioassayed against several soil insecticides along with laboratory reared larvae of the predatory carabid Pterostichus melanarius Illiger. Adult S. comma beetles were exposed to serial dilutions of insecticides using a Potter spray tower; larvae of P. melanarius were exposed to insecticidally treated Plainfield sand. Fensulfothion, phorate, methomyl, carbofuran, and O,O-diethyl-S(tertbutylthio) methyl phosphorodithioate (Counter®) proved to be highly toxic to adult S. comma with a 0.01% solution causing mortalities > 65%. In the bioassay of P. melanarius larvae, Counter®, phorate, heptachlor, aldrin, and O-(2-chloro-1-(2,5-dichlorophenyl)vinyl) O-methyl ethylphosphonothioate (WL 24073) produced mortalities > 75% at 0.1 p.p.m. in Plainfield sand. The Pterostichus larvae which are probably important as predators of pest insects appear quite susceptible to several important soil insecticides. Chlorfenvinphos, leptophos, and p,p′-DDT were fairly innocuous to both adults and larvae.

Wireworms: Efficacy of Various Insecticides for Protection of Potatoes in Southern Alberta1

Granular fonofos, and granular AC 92100 [ O, O -diethyl S-( t -butylthio) methyl phosphorodithioate], each at 2 lb AI acre in-furrow, gave excellent protection of potatoes against wireworms in irrigated soils of southern Alberta. Fonofos was particularly effective over 2 consecutive years and provided better control than registered chlordane or carbofuran in-furrow broadcast. Chlordane and carbofuran were not significantly better than the checks in several tests, and HCS-3260 (alpha gamma chlordane) was no more consistent in its protection of potatoes than was chlordane. Fensulfothion, ( O, O -diethyl O-p -[(methylsulfinyl)phenyl] phosphorothioate), applied in-furrow or broadcast, gave variable tuber protection but appeared to be slightly better than chlordane or carbofuran. Fonofos, AC 92100, fensulfothion, and PP211 [ O, O -diethyl O -(2-diethyl-amino-4-methyl-6-pyrimidinyl) phosphorothioate] were as effective against the sugarbeet wireworm, Limonius californicus (Mannerheim), as against the prairie grain wireworm, Ctenicera aeripennis destructor (Brown).

Interaction of Prometryne and Phorate on Bean

The absorption by bean(Phaseolus vulgarisL. ‘Black Valentine’) of 2,4-bis-(isopropylamino)-6-(methylthio)-s-triazine (prometryne) at 1 μM concentration was increased in the presence of 10, 1, or 0.1 μMO,O-diethyl S-(ethylthio) methyl phosphorodithioate (phorate). An increase in absorption of 10 μM prometryne with addition of 1 μM phorate was recorded after 72 hr, but no increase was seen after 96 hr of absorption. Both prometryne and phorate inhibited state 3 respiration of mitochondria isolated from 6-day-old bean hypocotyls. Inhibition increased with increasing pesticide concentrations. When the pesticides were applied simultaneously, no interactions affecting state 3 respiration were observed. Neither prometryne nor phorate alone significantly affected phosphate accumulation by bean shoot mitochondria.

Relative Toxicity of Pesticides to Organophosphorus-Resistant Orchard Populations of Neoseiulus fallacis and Its Prey12

Two strains of the phytoseiid Neoseiulus (Typhlodromus) fallacis (Garman) from different North Carolina apple orchards showed a high to moderate degree of resistance to azinphosmethyl and parathion when compared to a strain that had not been exposed to these compounds. One of the resistant strains was further tested and results showed a moderate degree of cross resistance to Gardona,® (2-chloro-1-(2,4,5-trichlorophenyl) vinyl dimethyl phosphate), and Imidan,® ( O, O -dimethyl Sphthalimido methyl phosphorodithioate), and a minor degree of cross resistance to Omite, (2-( p - tert -butylphenoxy) cyclohexyl 2-propynyl sulfite). Plictran® (tricydohexyltin hydroxide) was shown to be more toxic to the organ phosphorus-resistant strain than the susceptible strain. The degree of organ phosphorus resistance in N. fallacis was the same or greater than in its prey, the European red mite, Panonychus ulmi (Koch), and the twos potted spider mite, Tetranychus urticae Koch, collected from treated orchards. The level of susceptibility of the 3 mite species to amite and Plictran was: European red mite> two spotted spider mite> N. fallacis .

Resistant Responses of the Tea Red Spider Mite, Tetranychus kanzawai KISHIDA, to Phenkapton, Estox, and Kelthane in the Tea Growing Areas in Japan

The author reported in the previous paper (OSAKABE, 1967) that in some of tea fields in Shizuoka prefecture, the tea red spider mite, Tetranychus kanzawai KISHIDA, was shown to gain the resistance to Phenkapton since 1961-62 and to Estox since 1964.This paper deals with the resistant responses of mites to Phenkapton, O, O-diethyl S-(2, 5-dichlorophenylthio)-methyl phosphorodithioate, Estox, O, O-dimethyl S-(1-methyl-2-ethylsulfinyl)-ethyl phosphorothibate, and Kelthane, 1, 1-bis-(P-chlorophenyl) 2, 2, 2-trichloroethanol, in many, districts of tea growing areas in Japan.As the results in 1965-'66, the mites were classified into the resistant and the susceptible groups. The LC50 values of the resistant and the susceptible mites to these chemicals were shown as follows Phenkapton ; resistant mites 166±34 ppm, susceptible mites 1.2±0.6 ppm, R/S ratio 138.3, Estox ; resistant mites 1182±510 ppm, susceptible mites 7.2±2.0 ppm, R/S ratio 164.2, Kelthane ; resistant mites 234 ppm, susceptible mites 3.8±1.9 ppm, R/S ratio 61.6. The mites were divided into three types owing to the resistibility to these chemicals.The first type is susceptible to Phenkapton, Estox, and Kelthane, the second type is resistant to Phenkapton and Estox, while susceptible to Kelthane, and the third type is resistant to above described three chemicals, respectively. The mites belonging to the first type were discovered in Kanto (Saitama), Shikoku (Kagawa, Tokushima, Kochi), and south Kyushu (Miyazaki, Kagoshima) districts, but the second type of mites widely distributed in Tokai-Kinki (Shizuoka, Aichi, Mie, Shiga, Nara) and north Kyushu (Fukuoka, Saga) districts. The third type of mites were very few, and it was discovered in Kyoto prefecture. From the correlation coefficients among the LC50, of three chemicals, it may be said that the cross-resistance could be noticed between Phenkapton and Estox, but not clearly between Kelthane and Phenkapton or Estox.

Spring and Fall Applications of Insecticides for Alfalfa Weevil Control—1963-641

Insecticide applications for control of the alfalfa weevil, Hypera postica (Gyllenhal), were made in the spring and fall using various materials in spray and granular formulations. None of the fall treatments (October) provided satisfactory control and neither heptachlor nor dieldrin were so effective against the weevil as they had been 2 years previously. Malathion and azinphosmethyl spray treatments applied in the spring (April) at 1.0 and 0.75 Ib per acre, respectively, provided the best protection against alfalfa weevil larvae. Several unregistered insecticides showed some promise for weevil control; these were: SD 4072 [2-chlor-l-(2,4-dichlorophenyl) vinyl diethyl phosphate]; SD 7438 (benzylidene methyl phosphorodithioate); American Cyanamid 47470 [2-(dicthoxyphosphinylimino)-4-methyl-1,3-dithiolane]; American Cyanamid 47772 [2-(dimethoxyphosphinylimino)-4 methyl-],3-dithiolane]; Imidan® ( O, O -dimethyl S -phthalimidometbyl phosphordithioate); and dimetilan.

Control of Certain Insects and Mites on Cotton with Three Systemic Organophosphorous Compounds1

The systemic organophosphorous insecticides phorate (O, O-diethyl S-(ethylthio )methyl phosphorodithioate), Di-Syston® (O, O-dicthyl S-[2-(ethylthio)ethyl] phosphorodithioate), and dimethoate (O, O-dimethyl S-(N-methylcarbamoylmethyl)phosphorodithioate) were evaluated for control of thrips populations (predominantly Thrips tabaci Lindeman); the cotton aphid, Aphis gossypii Glover; the leafminer Liriomyza pictella (Thomson); the strawberry spider mite, Tetranychus atlanticus Mc-Gregor; the two-spotted spider mite, T. telarius (Linnaeus); and the Pacific spider mite, T. pacificus McGregor. When applied at planting time, phorate as a carbon powder (44D)seed treatment at 0.5 to 2.5 lbs. per acre and phorate and Di-Syston as granular formulations placed in the soil at 1.2 to 6.9 lbs. per acre controlled the above pests. Sidedress applications of the above materials, and of dimethoate, to growing cotton gave variable results. Phorate at 1.3 to 3.5 lbs. and dimethoate at 1.1 to 1.5 lbs. per acre controlled the 3 species of spider mites in some locations, hut failed in others. Di-Syston side dressed at 1.4 to 3.8 lbs. per acre was not effective. An infestation of L. pictella in one location was controlled with the phorate side dress at 1.7 lbs. per acre. Failures of phorate and dimethoate to control spider mites in some locations appeared to relate to soil types. Spider mites in all of the locations were resistant to foliar sprays of derueton (mixture of O, O-diethyl S (and O)-2-(ethylthio)ethyl phosphorothioates) and related compounds.

The Metabolism of Phorate, an Organophosphorus Insecticide, in Three Insect Species

The oxidative metabolic pathway of phorate (formerly known as Thimet) (O,O-diethyl S-(ethylthio)methyl phosphorodithioate) was studied in three insect species in vivo. Metabolites were separated by paper chromatography with β-methoxypropionitrile as stationary phase and cyclohexane as moving phase and detected by use of 2,6-dibromo-N-chloro-p-qninoneimine which gives yellow to red colors. The sensitivity is 1 to 5 µg. of phorate or its metabolites. The chief product from phorate applied to the German cockroach (Blattella germanica (L.)), large milkweed bug (Oncopeltus fasciatus (Dallas)), and the bug (Rhodnius prolixus Stahl) is the sulfoxide and/or sulfone of phorate. No evidence was obtained indicating importance of a possible secondary pathway involving formation of the oxygen analog of phorate and its two oxidized derivatives in vivo. The latter two compounds are not readily identified on paper chromatograms. The oxygen analog of phorate was very rapidly degraded in vivo.

Effect of Insecticides on Emergence of Sugar-Beet Seedlings and on Control of the Sugar-Beet Root Maggot

Both heptachlor-impregnated triple superphosphate (0-43-0) and heptaehlor-impregnated ammonium phosphate (11-48-0) at 1 lb. of toxicant per acre significantly reduced damage by the sugar-beet root maggot, Teta/wps myopaeformis (RÖder). Ethion (Niagara Brand Spray Company Limited) at ] lb. per acre, Trithion ® ( O,O -diethyl S(p-ehlorophenylthio)methyl phosphorodithioate (Stauffer Chemical Company, Portland, Oregon)) at lib. per acre and seed treatments with heptachlor at both] and 2 oz. per acre also reduced maggot damage. The heptachlor-impregnated ammonium phosphate at 1 lb. of toxicant per acre a seed treatment with heptachlor at 4 oz. per acre, and Bayer 29493 ( O,O -dimethyl O -[4-(methylthio)-m-tolyl] phosphorothioate (Chemagro Corporation, Kansas City, Mo.)) at 1 Ib. per acre significantly reduced emergence of seedlings, and the latter treatment gave little control of the maggot. The sugarbeet root maggot was most effectively controlled in southern Alberta with 1 lb. of heptachlor per acre placed in the drill row with the seed or 3 Ib. per acre of heptachlor placed in a 5-inch hand over the row. These two treatments, however, left residues of heptachlor and heptachlor epoxide in the sugar-beet roots at harvest.

Field Experiments on Insecticidal Control of Insect Pests of Cabbage and Broccoli1

Weekly applications of Thiodan® (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-ructhano-2,4,3-benzodioxathiepin-3-oxide) or Dibrom® (1,2-dibromo-2,2-dichloroethyl dimcthyl phosphate) gave better control of cabbage looper, Trichoplusia ni (Hbn.), and imported cabbage worm, Pieris rapae (L.), based on percentage of undamaged cabbage heads harvested than Methyl Trithion® ( O,O -dimethyl S -( p -chlorophenylthio) methyl phosphorodithioate), phosphamidon, Kepone® (decachlorooctahydro-1,3,4-metheno-2 H -cyclobuta[ed] pentalen-2-one) or methoxychlor. Against cabbage looper on broccoli, dimethoate, Dibrom, or Thiodan followed by combinations of Dibrom and Perthane® (1,1-dichloro-2,2-bis ( p -ethylphenyl)ethane), and malathion and Perthane, gave higher reduction of cabbage looper in the heads at harvest than Methyl Trithion, phosphamidon, Thiodan (at one-half recommended dosage) or Am. Cyanamid 24055 (1,1-dimethyl-3-( p -acetamidophenyl) triazene). The latter, an antifeeding compound, significantly reduced feeding injury over untreated plots. Dimethoate is a particularly promising insecticide for control of cole crop insects.

Preliminary Evaluation of Animal Systemic Insecticides

When 17 compounds were found to be active as systemic insecticides in preliminary laboratory tests with guinea pigs, tests were conducted by treating small numbers of cattle with these compounds and Bayer 23129 ( O,O -dimethyl S -2(ethylthio) ethyl phosphorodithioate) to determine their systemic effect against cattle grubs ( Hypoderma spp.). Bayer 29493, Dowco 105, and Stauffer R-2371 gave 95% to 100% control of grubs at dosages tolerated by the cattle. The rest were ineffective or inconsistently effective or effective at dosages toxic to cattle. The chemical names of the effective compounds are Bayer 29493 ( O,O -dimcthyl O -(4-methylthio- m -tolyl) phosphorothioate), Dowco 105 ( O -(4- tert -butyl-2-dllorophenyl) O -methyl ethylphosphoramidothioate), and Stauffer R-2371 ( O,O -diethyl bis-(4-chlorophenyl) methyl phosphorodithioate).