Effects of spring spot dose response herbicide applications for the control of cane needle grass ('Nassella hyalina') patches in non-arable situations on the Victorian volcanic plain

Cane needle grass (Nassella hyalina (Nees) Barkworth) is an exotic, perennial, unpalatable, weedy grass from South America threatening critically endangered indigenous grasslands within the Victorian Volcanic plain. This trial examined dose response applications of spot herbicide treatments (glyphosate, flupropanate, flupropanate granules and fluazifop-p) applied individually onto patches of cane needle grass at a field site near Werribee during spring 2014. Cane needle grass survival and damage assessments were made at 1 week, 1 month, 3 months, 6 months and 13 months after treatment. Fluazifop-p and glyphosate induced the most rapid foliage damage with higher rates producing apparent control after 3 months. Glyphosate rates above 7 mL L-1 resulted in more than 30% cane needle grass mortality while fluazifop-p at the highest rate of 20 mL L-1 resulted in 48% mortality. Both these post-emergent, foliar-absorbed, translocated, broad-spectrum herbicides performed better when applied in spring than compared to a previous equivalent trial where herbicide was applied in autumn. All rates of the liquid flupropanate formulation caused more than 80% severe damage/death, but more than 25% of plants were still surviving 13 months after treatment. It is believed that the lower rainfall experienced during 2014-15 and cool winter temperatures have yet to fully activate this herbicide. The granulated formulation of flupropanate was less effective than the liquid formulation under these conditions suggesting that the granular formulation may be more reliant on weather conditions for activation than the liquid formulation.