Experiments on diffusion of phosphine in cut flower boxes

Abstract

One of the most effective fumigants for disinfestation of cut flowers is currently methyl bromide, soon to be restricted. Toxicity of a potential alternative fiimigant, phosphine (2% PH3 + 98% N2), was tested earlier on insect pests of cut flowers. Effective concentrations and durations of fumigation by phosphine have been ascertained in vitro, but the efficacy of phosphine under commercial situations needs to be examined. Numerical modelling indicates that in still conditions it may take over 700 min for phosphine to equilibrate at the center of an empty fibreboard box 1.0 m × 0.3 m × 0.21 m. For flowers such as proteas with large, tight bracts covering the flower, the time for these fumiga..