Wednesday, November 15, 2006 - 2:55 PM

Controlling Soil-Borne Plant Pests Using Members of the Brassicaceae.

Matthew Morra, Univ of Idaho, Division of Soil & Land Resources, Univ. of Idaho, Moscow, ID 83844-2339

Canola and other members of the Brassicaceae contain compounds called glucosinolates that when enzymatically hydrolyzed form a variety of biologically active chemicals of potential value in controlling soil-borne plant pests in a process termed biofumigation.  Although we can predict pesticidal activity of Brassicaceae tissues by measuring glucosinolate concentrations, actual pest control efficacy frequently deviates from expectations.  It is imperative that we fully understand the chemical and physical processes controlling glucosinolate hydrolysis, pesticidal release from the tissues, and biological activity of the products in the soil environment to optimize the use of canola and other Brassicaceae species in pest control strategies.  Initial consideration must be given to selecting plant varieties high in concentrations of specific glucosinolates proven to be biologically active in laboratory bioassays.  Purified compounds, tissues, or quantitative structure-activity relationships can be used to identify the most biologically active hydrolysis products against the targeted plant pest.  Multiple compounds may be involved in pest inhibition and at least some of these compounds may not be produced from glucosinolates.  The next step is to maximize glucosinolate hydrolysis and release of the toxic compounds by extensively macerating the tissues and providing sufficient water to promote hydrolysis. Once in soil, the fate of glucosinolate hydrolysis products within the three-phase system must be predicted using the same techniques as those for synthetic pesticides. In contrast to commercial pesticides however, tissues contain other potential allelochemicals and contribute large amounts of organic carbon that may positively or negatively influence pest control efficacy.  Controlling soil-borne plant pests with glucosinolate hydrolysis products is highly likely if we can adequately address complex relationships that occur when using plants tissues as a source of pesticidal compounds.