Incompatibility of metam sodium with halogenated fumigants

Abstract

Metam sodium (metam) is a widely used soil fumigant. Combined application of metam and other available fumigants is intended to produce synergic pesticidal effects for a broad spectrum of pest control in soil fumigation. This study aimed to test the compatibility of metam with the halogenated fumigants 1,3-dichloropropene (1,3-D), chloropicrin, methyl bromide, methyl iodide and propargyl bromide. Halogenated fumigants and metam were spiked simultaneously into organic solvents, water and moist soils, and metam-induced degradation of these halogenated chemicals was evaluated. In all three media, the halogenated fumigants were incompatible with metam and degraded via rapid chemical reactions. The degradation rate varied with halogenated fumigant species and increased as the amount of metam present was increased. In moist soil, 15-95% of the halogenated fumigants were decomposed within 72 h by metam at a 1:1 molar ratio. Combined application of Telone C-35 (62.5% 1,3-D + 35% chloropicrin) at 265 mg kg(-1) and Vapam (42% metam) at 567 mg kg(-1) in soil resulted in complete disappearance of the applied chloropicrin and 20-38% of the 1,3-D within 8 h. The results suggest that simultaneous application of halogenated fumigants and metam at the same soil depth will not maximize pest control. In practice, sequential treatment of soil or application at different soil depths is recommended when these two types of fumigants are used in combination.

Effect of application timing and method on efficacy and phytotoxicity of 1,3‐D, chloropicrin and metam‐sodium combinations in squash plasticulture

“…Simultaneous application of metam‐sodium and halogenated fumigants (e.g. chloropicrin and 1,3‐D) was found to accelerate the degradation of the halogenated fumigants, reducing their availability in the soil 37, 38. The relatively high application rates in the present tests possibly masked this effect, or the transformation of chloropicrin and 1,3‐D occurs more rapidly in California than in Georgia soils.…”

Evaluation of the combination of 1,3‐dichloropropene and dazomet as an efficient alternative to methyl bromide for cucumber production in China

“…Previous studies have found that the simultaneous application of MNa and halogenated fumigants (e.g. Pic and 1,3‐D) was found to accelerate the degradation of the halogenated fumigants, reducing their availability in soil 36, 37. The present laboratory trials on the combined application of 1,3‐D + DZ did not indicate this type of degradation; however, the relatively high application rates in the present tests possibly masked the effect 4…”

Evaluation of the Combination of Dimethyl Disulfide and Dazomet as an Efficient Methyl Bromide Alternative for Cucumber Production in China

“…33,34 However, the combined application of DMDS plus DZ did not exhibit degradation according to the positive synergistic effects observed from the different rates tested in our laboratory. It has been reported that relatively high application rates may possibly mask degradation; 4 however, both high and low rates were tested in our laboratory studies.…”