Biofumigation: environmental impacts on the biological activity of diverse pure and plant‐derived isothiocyanates

Abstract

Four pure isothiocyanates (methyl, 2-propenyl, benzyl and 2-phenylethyl isothiocyanate), hydrolysing tissue of two brassicas rich in either 2-propenyl or 2-phenylethyl isothiocyanate, and the methyl isothiocyanate-generating pesticide metam-sodium were tested in vapour exposure tests for biological activity against a model soil insect both in vitro and in the presence of three contrasting soils and under four temperatures from 5 to 20 degrees C. The purpose was to develop an understanding of the factors controlling isothiocyanate release and maintenance in soil in order to identify advantageous attributes to seek in utilising brassicas for isothiocyanate-based biofumigation. Methyl isothiocyanate, structurally the simplest and the most volatile, was the most biologically active isothiocyanate under all conditions. It was less affected by the presence of soil and by lower temperature than the longer-chain aliphatic 2-propenyl isothiocyanate. The activity of the less volatile aromatic isothiocyanates was reduced much more by soil, with a decline up to many thousand-fold in the presence of soil with high organic matter content at lower temperature. Metam-sodium closely reflected the methyl isothiocyanate results. The results indicate that brassicas rich in aliphatic isothiocyanates are more likely to have the potential to exert stronger isothiocyanate-based biofumigation effects than those similarly rich in aromatic isothiocyanates.

Defence mechanisms of Brassicaceae: implications for plant-insect interactions and potential for integrated pest management. A review

“…Isothiocyanates carry fumigant properties similar to metham-sodium Warton et al, 2003). Metham-sodium (sodium N-methyldithiocarbamate) is a compound that is used globally to control noxious soil-borne organisms in intensive cropping systems as it generates the wide-spectrum fumigant-like compound methyl isothiocyanate after coming into contact with the wet soil (Matthiessen and Shackleton, 2005). Methyl isothiocyanate (not present in brassicas) is the only isothiocyanate which is used as a pesticide on a commercial basis but other isothiocyanates have also become the subject of interest due to their biofumigation properties (Angus et al, 1994).…”

“…The phasing out of the ozone-depleting soil fumigant methyl bromide and a higher interest in developing safe and economically viable insect pest management strategies has led to the initiation of alternative approaches. One of these approaches was the process of biofumigation by using macerated Brassica tissues as biofumigant agents and as cover crops (Noble et al, 2002;Matthiessen and Shackleton, 2005;Montfort et al, 2007). The biofumigation process potentially fulfils the requirements of a safe and economical pest management strategy and is included as a non-chemical alternative to methyl bromide by the Methyl Bromide Technical Options Committee (MBTOC, 1997), as documented by Ploeg (2008).…”

“…was the most tolerant, while Aphanomyces, Gaeumannomyces, Phytophthora and Thielaviopsis were very sensitive to 2-phenylethyl isothiocyanate. Matthiessen and Shackleton (2005) tested four pure isothiocyanates (methyl, 2-propenyl, benzyl and 2-phenylethyl isothiocyanate), in vapour exposure tests for biological activity against the model soil insect whitefringed weevil both in vitro and in the presence of three contrasting soils and under four temperatures. The results indicated that brassicas rich in aliphatic isothiocyanates are more likely to have the potential to exert stronger isothiocyanatebased biofumigation effects than those similarly rich in aromatic isothiocyanates.…”

Solarização em microcosmo: efeito de materiais vegetais na sobrevivência de fitopatógenos de solo e na produção de voláteis

“…Há vários fatores apontados como responsáveis pela ação dessa associação: temperatura resultante da solarização (22); comunidade microbiana decompositora estimulada pela presença dos materiais vegetais incorporados ao solo (6, 7, 18); atmosfera anaeróbica (26); e compostos voláteis resultantes da decomposição dos materiais vegetais (19). Dentre esses, os compostos voláteis são apontados como o diferencial quanto à eficácia no controle de fitopatógenos habitantes de solo, sobretudo os oriundos de brássicas (3,11,12,21,22).…”

Biological and other soil parameters response to winter cover crops in a mediterranean irrigated system

“…The incorporation and decomposition of the radish (and other Brassicaceae) can generate a flush release of ITC compounds which can delay AMF colonization and the formation of arbuscules (Gavito and Miller, 1998), which may have been the case in the oats. Over time the ITC compounds disappear through volatilization and microbial decomposition of the ITC (Matthiessen and Shackleton, 2005), that way allowing the revival of the AMF inoculum, which may have happened for endive.…”