Herbicides ametryne

Lopez A, Mascolo G, Tiravanti G, Passino R (1997) Degradation of herbicides (ametryn and isoproturon) during water disinfection by means of two oxidants (hypochlorite and chlorine dioxide). Water Sci Technol 35 129-136... 

Pesticides and herbicides ametryne, atrazme, benzyl benzoate,... 

A modified release system for the herbicide ametryn was developed by Grillo and co-workers [24] via encapsulation of the active substance in polymer P(3HB) and poly(3HB-co-3HV) microparticles in order to improve the herbicidal action and minimise environmental impact. Nearly 100% release of free ametryn was observed after 1.2 days compared with a significantly reduced herbicide release, 75 and 87% respectively, over the same period of time for P(3HB) and poly(3HB-CO-3HV) microparticles. A slower and more sustained release is a desirable feature in the use of herbicides as it diminishes the impact on the ecosystem, human health and environment. Prudnikova and co-workers [25] presented the first report of the use of PHA/ herbicide matrices to kill weeds. They reported that the herbicide Zellek Super, loaded into copolymer poly(3HB-co-3HV) carriers, was more effective than when it was applied traditionally as a spray onto plants during the tillering phase. However, the inhibitory effect on soil microorganisms was reduced by the encapsulation of the herbicide in the polymer matrix but its effectiveness against test plants was maintained. 

PHA can be used in the controlled release of insecticides, which can be integrated into the pellets and sown along with the farmer s crops. The insecticide would be released at a rate related to the level of pest activity since the bacteria breaking down the polymer would be affected by the same environmental conditions as that of the soil pests [5]. For example, micro- and nanoparticles of P(3HB) and P(31TB-co-3ITV) were used in the controlled release formulation of the herbicide ametryn [251]. 

Ureides (e.g., diuron, linuron) and triazines (e.g., atrazine, simazine, ametryne) all act as inhibitors of photosynthesis and are applied to soil (see Figure 14.1 for structures). They are toxic to seedling weeds, which they can absorb from the soil. Some of them (e.g., simazine) have very low water solubility and, consequently, are persistent and relatively immobile in soil (see Chapter 4, Section 4.3, which also mentions the question of depth selection when these soil-acting herbicides are used for selective weed control). 

Oxidation of triazine herbicides with chlorine and chlorine dioxide has been widely studied [105-108]. In the case of sulfur-containing triazines, oxidation occurs mainly via cleavage of the weakened R-S-CH3 bond rather than by addition of chlorine. Reactions of S-triazines with chlorine are faster than with chlorine dioxide, and form sulfoxide, sulfone, and a sulfone hydrolysis product. Chlorination with chlorine dioxide only produced sulfoxide [108]. Lopez et al. identified the formation of sulfonate esters during the chlorination of ametryn and terbutryn [106, 107]. Triazine DBFs identified by Brix et al. exhibited higher toxicities than the parent compounds [105]. Similar to triazines, clethodim, a cyclohexanedione herbicide, is oxidized by hypochlorite and chloramines to clethodim sulfoxide and then to sulfone [109]. 

Alkylthiotriazines. In our laboratory we have studied the metabolic fate of 2-(4-ethylamino-6-methylthio- -triazin-2-ylamino)-2-methylpropionitrile (cyanatryn, 1, Fig. 1). This compound is a member of a class of herbicidal -triazines which also includes ametryne, prometryne and terbutryne. We were interested to note ( ) that two of the major metabolites of cyanatryn were the mercapturic acids 2-[A-ethylamino-6-(N-acetylcysteinyl)- -triazin-2-ylamino]-2-methylpropionitrTle (2.1) and its N-de-ethyl derivative (2.2) (Fig. 2). This pathway had not hitherto been reported for this class of compound. 

Ametryn and other triazines herbicides in tap water NS MIP-based cartridge < 1 ug/L. However, low recovery (10-40%) Ferrer and Barcelo, 1999... 

Most producers concentrated their production on the major triazines (e.g., atrazine, simazine, terbuthylazine, ametryn, and terbutryn). The producers of triazine herbicides through the 1990s are presented in Table 3.1, and producers since 2000 are listed in Table 3.2. 

The triazine herbicides can be divided into four different structural classes chlorotriazines, methylthiotriazines, methoxytriazines, and atypical or asymmetrical triazines. The chlorotriazine group includes atrazine, simazine, pro-pazine, terbuthylazine, and cyanazine. The methylthiotriazine group includes ametryn, prometryn, and terbutryn. The methoxytriazine group will include prometon and secbumeton. Hexazinone and metribuzin were chosen to represent the atypical triazine group. The plant metabolism of the most researched member of each triazine group will be discussed in detail to cover all major biological and chemical transformations reported in the literature. 

Selective herbicides are relatively recent developments in the 5000-year history of sugarcane production. After 1945, when phenoxy herbicides were first sold, one person using 2,4-D in a backpack sprayer could accomplish the work of 15 others using hoes and with far more lasting results than simply severing weeds with a steel tool at the soil surface. While three herbicide families (triazines, phenoxys, and dinitroanilines) are of major importance in sugarcane production, the triazines, atrazine and ametryn clearly predominate. 

Furthermore, the triazine herbicides have freed operators from much of the laborious burden of weed control, enabling them to manage other resources to maximize returns of both agricultural and milling operations. Since atrazine and ametryn were introduced, the genetic potentials of sugarcane cultivars have been more fully realized because the soil tillage and water losses have been reduced. 

The sugarcane industry in the United States and worldwide is highly dependent on the continued availability of triazine herbicides. In the United States, growers use reduced quantities of atrazine by applying it as a band over the row. Ametryn is strategically important as a postemergence treatment. The loss of any of the most essential sugarcane... 

Numerous herbicides are available for the diversity of soils, climates, and environmental conditions, based on research by the South Africa Sugar Association Experiment Station. Major herbicides include ametryn, alachlor, atrazine, hexazinone, and metribuzin. 

Ametryn, another triazine herbicide, was previously used for weed control in citrus. This herbicide first appeared in recommendations in 1979 for control of broadleaf weeds, annual grasses, and some perennial grasses. Ametryn was recommended at use rates of 3.6-7.2kg a.i./ha, with a maximum of 5.4kg a.i./ha for both shallow, poorly drained flatwood soils (soils having more organic matter and clay) and bedded groves (trees planted on raised beds). It was recommended that ametryn should not be applied to trees less than 2 years old. Between 1984 and 1988 the application rates were increased to 7.2-10.8kg a.i./ha, with the annual rate not to exceed 13.6kg a.i./ha, and with lower rates... 

Beginning in the 1950s, when triazines such as simazine, atrazine, prometryn, and ametryn were first synthesized and tested as selective herbicides in the Geigy laboratories in Basel, Switzerland (Gast et al 1955), massive research efforts have focused on the transformation and use of these compounds in the environment. The -triazines represent one of the most widely used and probably the most extensively studied family of herbicides. One of the driving forces for this research was the outstanding performance of triazines with respect to their selective herbicidal effects and crop tolerance. 

Substitution of the chlorine atom on ring C 2 of atrazine with a methylthio group impaired the ability of Pseudomonas strain ADP (Mandelbaum et al., 1995) or Pseudomonas strain YAYA6 (Yanze-Kontchou and Gschwind, 1995) to mineralize herbicides such as ametryn. 

McMartin, D.W., J.V.Headley, B.P. Wood, and J. Gilles (2003). Photolysis of atrazine and ametryne herbicides in Barbados sugarcane plantation soils and water. J. Environ. Sci. Health. B, 38 293-303. 

---