Biocidal plant dried pellets for biofumigation

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The presence in all Brassicaceae plant organs of high amounts of glucosinolates, and of the enzyme myrosinase that catalyses their hydrolysis, linked to the high biocidal activity of some glucosinolate enzymatic hydrolysis derivative products (mainly isothiocyanates and nitriles) have suggested the practical possibility of amending soil with these natural biocidal compounds by the cultivation and green manure of selected species of this family. The application of this technique even at full field level has given, in recent years, interesting applicative results, with clear advantages for the following crop yield (e.g. strawberry), if compared with an untreated soil or a conventional green manure, evidencing that the glucosinolate–myrosinase system may provide a natural alternative for methyl bromide soil fumigation. In this paper, some preliminary results of a study on the possibility of drying some of these selections to produce biocidal pellets to be used as organic treatments in addition or in alternative to biocidal green manure are reported and discussed. The first target was to limit, during drying, glucosinolate leakage and myrosinase activity loss; in this way, in fact, dry plants should be able to produce in soil the biocidal compounds when watered by irrigation. Using a simple drying up lab technique, it was possible, for some selections, to lose <40% of starting glucosinolate and to preserve myrosinase activity at a sufficient level. These results could be further improved using industrial dehydration plant. The dried plants, after water addition, showed, in vitro, a good fungitoxic activity on Pythium ssp. and Rhizoctonia solani, confirming the results obtained in similar tests with pure glucosinolate and pure myrosinase. These results open interesting applicative perspectives for this new raw material probably even as a natural alternative to methyl bromide.