Pirimicarb and its metabolite residues in lettuce. Influence of cultural environment

Abstract

The fate of Primicarb (I) residue on field and greenhouse lettuce was studied. The parent compound was quickly transformed into its N-methyl-N-formyl (11) and N-demethyl (111) analogues. Five days after treatment, another metabolite, N-demethylphenol (VI), was determined, though in low amounts. These metabolites were rapidly degraded, and 10 days after application of Pirimicarb, only I11 was detected, showing a very low residue. The very rapid decay rate of Pirimicarb into its metabolites should indicate that volatilization does not represent the primary means of loss of I in plants and that the aphicide action could also be ascribed to its metabolic products. Though the microclimatic conditions were different in the two experiments, the degradative kinetics were similar in both cases, because in the field relative humidity and wind speed, compensating for each other, determined a tendency to evaporation analogous to that occurring in the greenhouse.Aphids are among the most important pests in the cultivation of lettuce. Of the numerous insecticides on sale, Pirimicarb, 2-(dimethylamino)-5,6-dimethylpyrimidin-4yl dimethylcarbamate (I) (Figure l ) , is one of the few to possess selective action against aphids but not against their natural predators.Pirimicarb is rapidly lost in plants after spraying, mainly by volatilization but also by photochemical and metabolic degradation. The major degradative products are the carbamate-containing metabolites I1 (2-[(methylformyl)amin0]-5,6-dimethylpyrimidin-4-y1 dimethylcarbamate) and I11 (2-methylamino-5,6-dimethylpyrimidin-

Residues, half-life times, dissipation, and safety evaluation of the acaricide fenpyroximate applied on grapes

“…Further, a number of environmental factors, particularly temperature, precipitation (and humidity), and air movement (Gennari et al 1985), affect pesticide persistence. Other factors depend on the properties of the plant and plant species, the nature of the harvested crop, structure of cuticle, stage and rate of growth, and the general condition of the plant, in addition to the relationship between treated surface and its weight and living state of the plant surface (Khay, Choi, and Abd El-Aty 2008;Tewary et al 2005;Cabras et al 1990;Malhat 2012;Malhat et al 2014).…”

Capillary electrochromatography-applicability to the analysis of pesticides and compounds of environmental concern and the theory of electroosmosis

“…The development of a method for the separation of the insecticide pirimicarb and related compounds (Figure 11) [41] was investigated using Exsil C18, the phase that had given the best performance for the separation of the phthalates. However in this instance increasing the aqueous content of mobile phase to give adequate Channel volume is per unit sphere volume.…”

Comparative study of the dissipation of triadimefon in greenhouse and field conditions

“…Degradation of pesticides on leaf surfaces have been found to follow first order [19,20] been simulated using a model which assumes an emission rate for the source that decays exponentially on time [21,22]. Thus, assuming that in the studied conditions the dissipation is due to degradation, which follow first order, and to volatilization, which flux decreases exponentially on time, we can writê where M o is the quantity of applied pesticide.…”