CGA-43089 [α-(cyanomethoximino)-benzacetonitrile], CGA-92194 {α-[(1,3-dioxolan-2-yl-methyl)imino] benzeneacetonitrile}, and MON-4606 [5-thiazolecarboxylic acid, benzyl ester, 2-chloro-4-(trifluoromethyl)], applied as seed treatments at 1.25 g/kg seed, prevented yield losses in grain sorghum [Sorghum bicolor (L.) Moench.] in the field due to metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], alachlor [2-chloro-2′, 6′-diethyl-N-(methoxymethyl)acetanilide] or acetochlor [2-chloro-N-(ethoxymethyl)-6′-ethyl-o-acetotoluidide] applied at 1.7, 2.2 and 1.7 kg/ha, respectively. CGA-92194, applied at 0.8 g/kg seed, prevented yield reduction from metolachlor applied at 4.5 kg/ha. MON-4606 was more effective in protecting grain sorghum when applied as a seed treatment than when applied in the furrow with a clay or sand granule as carrier.

CGA-43089 [α-(cyanomethoximino)-benzacetonitrile] seed treatment was evaluated at three Nebraska locations during 1979 and 1980 for grain sorghum [Sorghum bicolor (L.) Moench] protection from injury by metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], four other chloroacetanilide herbicides, and three metolachlor + s-triazine combinations. Acetochlor [2-chloro-N-(ethoxymethyl)-6′-ethyl-o-acetotoluidide] caused the most frequent and severest injury to unprotected and protected sorghum. Soilincorporated metolachlor produced more consistent injury than preemergence application to unprotected sorghum, but placement did not affect CGA-43089 protection. Sorghum-stand reduction was the type of injury most frequently encountered, but crop yield was least affected. CGA-43089 always protected the grain sorghum from yield reduction with these herbicides.

A herbicide safener, CGA-43089 [α-(cyanomethoximino)-benzacetonitrile], has been discovered which will allow the safe use of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethylacetamide] in grain sorghum [Sorghum bicolor (L.) Moench]. Experiments revealed that sorghum is protected from injury by metolachlor when it is applied at rates as high as 4 kg/ha. Better protection was achieved when sorghum seed were treated directly with the safener than when it was mixed with the herbicide. A CGA-43089 rate of 1.25 to 1.5 g per kg of sorghum seed was adequate for protection. Sorghum tolerance to metolachlor was maintained with CGA-43089 when metolachlor was combined with several s-triazine herbicides. Metolachlor effectively controlled several annual grasses with an increase in sorghum yield.

Field studies were conducted on a Taloka silt loam (Mollic Albaqualf) to determine the effects of residual levels of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] on rice (Oryza sativa L.). Yield reductions could be overcome by increasing rice seeding rate, by decreasing seeding depth, or by applying the safeners CGA-43089 [α-(cyanomethoxyimino)-benzacetonitrile] or CGA-92194 [α-(1,3-dioxolan-2-yl-methoximino)-benzacetonitrile] to the rice seed. Greenhouse studies with the safeners and reduced seeding depths indicated that CGA-92194 was better than CGA-43089 for protecting rice from metolachlor injury, but reduced seeding depths did not reduce metolachlor injury.

Sorghum [Sorghum bicolor (L.) Moench. ‘G-623 GBR’] bioassays indicated that shoot growth was more susceptible to metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] and more responsive to the antidote CGA-92194 {α-[(1,3-dioxolan-2-yl-methoxy)-imino] benzeneacetonitrile} than root growth. Seed treatment with CGA-92194 increased seedling shoot tolerance to metolachlor approximately tenfold. CGA-92194 seed treatment enhanced shoot absorption of 14C-metolachlor approximately twofold. Metolachlor was initially metabolized to the glutathione conjugate in untreated shoots and those treated with CGA-92194. However, CGA-92194 seed treatment caused accelerated metolachlor metabolism in the shoot, decreasing metolachlor content and increasing formation of the glutathione conjugate. Cyometrinil {(Z)-α[(cyanomethoxy)imino] benzeneacetonitrile}, flurazole [phenylmethyl 2-chloro-4-(trifluoromethyl)-5-thiazolecarboxylate], naphthalic anhydride (1H,3H-naphtho[1,8-cd]-pyran-1,3-dione), and dichlormid (2,2-dichloro-N,N-di-2-propenylacetamide) also protected sorghum from metolachlor injury and enhanced metolachlor absorption and metabolism. The degree of protection conferred by a particular antidote was correlated with its ability to enhance metabolism of metolachlor in shoot tissue. These results are consistent with the hypothesis that the above antidotes protect sorghum from metolachlor injury by inducing rapid detoxification of metolachlor through conjugation with glutathione.

Certain oximes, including cyometrinil [(Z)-α-(cyanomethoxy)iminobenzeneacetonitrile], CGA-92194 [N-(1,3-dioxolan-2-yl-methoxy)-iminobenzeneacetonitrile], 2-pyridinealdoxime-O-benzyl ether (PA-B), and 2-pyridinealdoxime-O-phenethyl ether (PA-PE), which are known to protect sorghum from chloroacetanilide herbicides, increased the toxicity of the insecticide propoxur (o-isopropoxyphenyl-methyl carbamate) to a resistant strain of housefly (Musca domestica L.). Flurazole [5-thiazolecarboxylic acid, benzyl ester, 2-chloro-4-(trifluoromethyl)], a nonoxime protectant for grain sorghum, had less effect on the toxicity of propoxur than did the oximes. Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], which can be used as a herbicide in sorghum [Sorghum bicolor (L.) Moench.] only if the seed have been treated with a protectant, also increased the toxicity of propoxur to houseflies. Commercially available insecticide synergists increase insecticide activity by inhibiting NADPH-dependent microsomal mixed-function oxidase activity. Sorghum coleoptiles possessed the enzyme system necessary to oxidize aldrin (1,2,3,4,10,10-hexachloro-1,4,4a,5,8,8a-hexahydro-1,4-endo-exo-5,8-dimethanonaphthalene) to dieldrin (1,2,3,4,10,10-hexachloro-6, 7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-1,4-endo-exo-5,8-dimethanonaphthalene), which is a standard test for oxidative metabolism in insects. Under the conditions of these tests, the aldrin epoxidase activity in sorghum coleoptiles was not affected by pretreatment with cyometrinil or flurazole.

Studies in growth chambers indicated that CGA-43089 {α-[(cyanomethoxy)imino] benzeneacetonitrile} applied at a rate of 1.25 g/kg of seed reduced the phytotoxicity of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], bensulide [o,o-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl) benzenesulfonamide], EPTC (S-ethyl dipropylthiocarbamate), UBI-S734 {2-[(1,2,5-dimethylphenyl)ethylsulfonyl] pyridine N-oxide} and MBR-18337 {N-[4-(ethylthio)-2-(trifluoromethyl)phenyl] methanesulfonamide} to grain sorghum [Sorghum bicolor (L.) Moench] during seed germination and seedling emergence. The protected sorghum tolerated metolachlor over a wider range of rates than it tolerated the other herbicides. CGA-43089 did not protect sorghum from the phytotoxicity of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). Of seven other oximes tested as seed treatments, dimethylglyoxime, benzophenone oxime, pyridine-2-aldoxime, benzoin-α-oxime, and methyl thioacetohydroxamate showed promise for increasing the tolerance of grain sorghum to metolachlor. In general, higher rates of these oximes than the rate of CGA-43089 were required for equivalent protection of sorghum.

R-25788 (N,N-diallyl-2,2-dichloroacetamide) and H-31866 [N-allyl-N-(3,3-dichloroallyl)dichloroacetamide] were more effective than CDAA (N,N-diallyl-2-chloroacetamide) in preventing yield reductions to corn (Zea mays L. ‘NB-611’) from alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] or metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] in the greenhouse. A CGA-43089 [α-(cyanomethoximino)-benzacetonitrile] seed treatment (1.25 g/kg) was more effective than a R-25788 tank mix in preventing yield reductions to grain sorghum [Sorghum bicolor (L.) Moench ‘G-623 GBR’] from alachlor or metolachlor in the greenhouse. Absorption of 14C-alachlor by sorghum seedlings grown in petri dishes, and absorption, translocation, and metabolism of 14C-metolachlor by sorghum seedlings grown in soil, were not affected by CGA-43089 seed treatment. Forage sorghum [Sorghum bicolor (L.) Moench ‘Rox Orange’] was used to simulate shatter cane [Sorghum bicolor (L.) Moench] in field plots. In the absence of Rox Orange, alachlor and metolachlor reduced sorghum grain yields. This yield reduction was prevented by a CGA-43089 seed treatment, but not by a R-25788 tank mix with herbicides. In plots seeded with 10,000 Rox Orange seed/57 m2, grain yields of sorghum increased as alachlor or metolachlor plus CGA-43089 rates increased. There was no grain yield response to any herbicide treatment in plots seeded with 50,000 Rox Orange seed/57 m2.

Greenhouse studies were initiated to determine the efficacy of four herbicide antidotes as protectants of corn (Zea mays L., ‘DeKalb XL72AA’ and ‘DeKalb XL67′) against injury from preemergence or early postemergence applications of the herbicides chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide}, fluazifop-butyl {butyl-2-[4-[5-(trifluoromethyl-2-pyridinyl)oxy] phenoxy] propanoate}, or BAS 9052 OH {2-[1-(ethoxyimino)-butyl]-5-[2-(ethylthio)-propyl]-3-hydroxy-2-cyclohexene-1-one}. NA (1,8-naphthalic anhydride) was the most effective of the four antidotes in protecting corn against injury from preemergence applications of chlorsulfuron. CGA-43089 [α-(cyanomethoxy)-imino-benzeneacetonitrile] and CGA-92194 [α-(1,3-dioxolan-2-yl-methoxy)-imino-benzeneacetonitrile] partially protected corn from chlorsulfuron injury, whereas R-25788 (N,N-diallyl-2,2-dichloroacetamide] was the least effective. R-25788 offered partial to good protection to corn against injury from preemergence applications of fluazifop-butyl and BAS 9052 OH. NA, or CGA-43089, and CGA-92194 partially protected corn from fluazifop-butyl injury but their efficacy against BAS 9052 OH injury to corn was limited. In general, all four antidotes offered better protection to the thiocarbamate-tolerant ‘XL72AA’ hybrid than to the thiocarbamate-susceptible ‘XL67’ hybrid. With the exception of NA, which partially protected corn from postemergence-applied chlorsulfuron, none of the four herbicide antidotes was effective in protecting corn against injury from postemergence applications of any of the three herbicides.