Effect of in Planta Treatment of 'Cavendish' Banana with Herbicides and Fungicides on the Colonisation and Sporulation by f.sp. Subtropical Race 4.

Fusarium wilt caused by the soil-borne fungus f.sp. () is a significant constraint to banana production worldwide, with the recent expansion of banana growing regions impacted by Tropical Race 4 (TR4). The lack of commercially acceptable Cavendish cultivars with resistance means the only current means of effective control is through strict quarantine and inoculum management. One method of control that is currently advocated includes the removal of infected plants which have been killed using herbicide injections. The aim of this work was to examine the effect of herbicide and fungicide treatments on sporulation of the fungus. In glasshouse studies using a green fluorescent transformed Subtropical Race 4 isolate, we found treatments with herbicide hastened colonisation of the banana tissue and the production of micro- and macroconidia. The use of a fungicide did not prevent sporulation of the fungus in such tissue. This study demonstrates that herbicide treated plants are a source of potential inoculum for infection of nearby plants.