Dicotyledonous weed

Ametryn is used for preemergence and postemergence control of both monocotyledonous and dicotyledonous weeds in corn, sugarcane, banana, pineapple, and noncrop areas. The metabolism of ametryn in com (Detra and Chib, 1990a), sugarcane (Detra and Chib, 1990b), and banana (Thalaker and Ash, 1996) has recently been studied, and the major findings will be summarized by individual crop. 

Blum U., King, L.D., Gerig, T.M., Lehman, M.E., Worsham, A.D. Effects of clover and small grain cover crops and tillage techniques on seedling emergence of some dicotyledonous weed species. Amer J Altern Agricul 1997 4 146-161. 

Blum, U., King, L.D., Brownie, C. Effects of wheat residues on dicotyledonous weed emergence in a simulated no-till system. Allelopathy J 2002 9 159-176. 

Tentoxin. AUernarla alternata produces tentoxin [61], a cyclic tetrapeptide. This phytotoxin causes Injury to many monocotyledonous and dicotyledonous weed species, but does not Injure maize (Zea mavs L.) or soybean (GTvcIne L. Nerr.) (29). Tentoxin has been synthesized In the lab (212) Sites of action of this toxin are disruption of energy transfer by Inhibition of CFi ATPase (211) and alteration of nuclear-coded protein uptake (2341. 

Introduced in 1982 by DuPont, this group has made a major impact on weed control technology. They are remarkable active compounds, selectively controlling many dicotyledonous weeds in cereals at very low dose rates, and they have very low mammalian toxicity. 

Ferrosulfate heptahydrate (FeSO 7HjO) is another compound with weak herbicidal action. Applied as an aqueous solution at rates of 6-12 kg/ha, it has been used for the postemergence control of dicotyledonous weeds in cereals. At rates of 100 kg/ha (in the form of a 10% aqueous solution) it can be used for the control of moss in turf. 

The uptake and translocation of dalapon is similar in sensitive and tolerant plants, so the toxicity of the compound to weeds must have another basis. Despite rapid absorption the phytotoxic action is manifested slowly. The leaves of sensitive plants curl and, starting from the margins, become yellow. The development of the plants stops, buds and roots cease to grow, and finally, the plants wither in 3-4 weeks. Se germination of dicotyledonous weeds is barely inhibited by dalapon, and even that of monocotyledons only at a high concentration. 

The salts and esters of 2,4-D are systemic foliage herbicides, with moderate soil herbicidal action. They are applied postemergence mainly in cereals, maize, rice, sugar cane and on pastures at a rate of 0.280-2.3 kg/ha active ingredient for the selective control of dicotyledonous weeds. At an application rate of 2.3 kg/ha, it is decomposed in about a month in the soil. 

Its held of application is similar to that of 2,4-D. It is used as a postemergence foliage herbicide in cereals, flax and on pasture land at a rate of280 g-2.25 kg active ingredient/ha. It is effective mainly for the control of dicotyledonous weeds, killing both annual and perennial weeds. Its herbicidal spectrum differs somewhat from that of 2,4-D. Cereals are more resistant to MCPA than to 2,4-D, while the reverse is true for maize. 

In maize, potato and peanut it is a selective herbicide eifective for the control of mono- and dicotyledonous weeds in the seedling stages. It is hydrolysed by moisture in the soil to 2,4-dichlorophenoxyethanol. 

The 1 1 mixture of 2-(2,4,5-trichlorophenoxy)ethanol (TCPE, 24) and atrazine (Buvinol ) is a selective pre- and postemergence herbicide with a broad range of herbicidal action. Many species of mono- and dicotyledonous weeds are sensitive to it in their various stages of development. Postemergence treatment is recommended in soils with extremely low humus content (below 1 %) because of the hazard of phytotoxicity, and in soils with extremely high humus content because of strong adsorption. 

Blackburn and Weldon (1964) described chloranocryl, the herbicidal properties of a compound closely related to propanil, N-(3,4-dichlorophenyl)methacrylamide (Dicryl ). This postemergence contact herbicide is selective in cotton against mono-and dicotyledonous weeds. It has now lost its commercial importance. 

The main field of application of dinitroaniline herbicides is the control of annual grass weeds. Some annual dicotyledonous weeds are also sensitive to dinitroaniline herbicides in the initial growth stage. All members of the group are fairly volatile, and are hence sprayed before sowing to the soil surface and immediately incorporated to a soil depth of 6-8 cm. Owing to their poor water solubility, they are not absorbed from dry soil in adequate quantity by the plant, so under dry conditions their action is unsatisfactory. 

Experiments of Centner (1966) with mono- and dicotyledonous weeds and crop plants showed that the biological activity of 2,6-dinitro-N,N-dialkylanilines substituted in position 4 with a CH, or a CFj group decreases if the total carbon atom number of the alkyl chains substituted at the amino nitrogen is more than six. 

Applied preemergence, dichlormate selectively controls mono- and dicotyledonous weeds in cotton, soybean, peanut, potato, garlic and ornamental plants. It can be used postemergence in rice for the control of barnyard grass (Echinochloa crus gain) and other annual grass weeds and broad-leaved weeds. 

CEPC is a preemergence selective soil herbicide for the control of mono- and dicotyledonous weeds. 

It can be used for the selective control of mono- and dicotyledonous weeds in onion, sugar beet, flower gardens and nurseries. It is used in combination with cycluron and pyramin (Fischer, 1960). 

Some of the problem dicotyledonous weeds, such as common lambsquarters (Chenopodium album), pigweed (Amaranthus retroflexus) and Russian thistle (Salsola kali), are resistant to asulam. On the other hand, as a postemergence herbicide asulam is effective against Rumex spp., Averui fatua and Pteridium aquilinum. 

It is effective against mono- and dicotyledonous weeds, particularly against black grass (Alpecurus myosuroides) in cereals. On winter cereals it is used at a rate of... 

Buturon (29) was developed by the BASF and introduced in 1966 (Fischer, 1964). In the soil, a dose of 1-2 kg/ha is microbially decomposed in 12 weeks. Buturon is effective as a pre- or postemergence herbicide against annual, shallow-root mono-and dicotyledonous weeds. An application rate of 1 kg/ha active ingredient is recommended in cereals, and 5 kg/ha on berry fruits and vine. The acute oral ld,(, for rats is 3000 mg/kg. It has no skin-irritating effect. 

Azido-4-ethylamino-6-t-butylamino-s-triazine (WL 9385,35) is efficient for the selective control of dicotyledonous weeds in grain, maize and potato. 2-Azido-4-isopropylamino-6-methylthio-i-triazine (aziprotryne, 36) is a selective herbicide efficient in the control of certain dicotyledonous weeds in cabbage, bean, sunflower, onion and maize, as is 2-azido-4-jec-butylamino 6-methylthio-j-triazine (C 8250, 37) in soybean and cotton. 

Both herbicides are absorbed mainly through the roots and kill monocotyledon-ous and dicotyledonous weeds efficiently. Owing to their lack of selectivity, they are primarily used on industrial and non-crop lands at a rate of 10 kg active ingredient/ha. 

Hydantocidin. A metabolite isolated from culture broths of Streptomyces hygroscopicus (SANK 63584) with a potent, non-selective herbicidal activity against annual and perennial monocotyledonous and dicotyledonous weeds. 

In the ALS of a Lactuca serriola biotype, highly resistant to SUs and moderately resistant to IMIs, Prol97 was substituted by His. The pyruvate binding domain on the ALS enzyme was not found to be altered by the mutation [57]. From Ko-chia scoparia it was reported that several substitutions of Prol97 by another amino acid (Thr, Arg, Leu, Gin, Ser, Ala) will confer resistance to sulfonylureas [58]. In the same spedes, it was found later that a substitution of Trp574 by Leu will also cause resistance to sulfonylureas and in addition cross-resistance to imidazoh-nones [59]. The latter substitution was also detected in resistant biotypes of several other dicotyledonous weed species. 

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