Extending flupropanate use - spot application on perennial mission and gamba grass

Abstract

Perennial mission grass (Cenchrus polystachios) and gamba grass (Andropogon gayanus) are two highly invasive grasses present in north Queensland. Currently, herbicide control options for these species are limited to non-selective herbicides such as glyphosate that result in significant off-target damage. In this study, field trials were conducted to investigate the efficacy of spot applications of flupropanate (liquid and granular) into the tussock as a selective herbicide option for these grasses. Australian Pesticides and Veterinary Medicines Authority (APVMA) approval will be sought for the use of: 4.5 g/tussock of GP Flupropanate and 0.6 ml/tussock of Tussock™ for perennial mission grass control; and 9 g/tussock of GP Flupropanate and 1.2 ml/tussock of Tussock™ for gamba grass control. These rates were selected as the most efficacious, although efficacy was not significantly higher than lower rates, it is expected that these rates will be more effective under marginal conditions. In summary, spot application of flupropanate is an effective and practical method for controlling these invasive grasses with particular application in areas such as revegetation sites, sites in the early stages of invasion with limited or scattered infestations and sites where the northern wet season can limit access for high-volume herbicide application.