Effects of Taskforceâ and Frenockâ on serrated tussock

Taskforceâ and Frenockâ) were applied to mature serrated tussock growing on soil derived from shale 10 km north of Tuena in the southern tablelands of NSW in summer/autumn 2000. Taskforceâ1 and Frenockâ were applied on 11 February 2000 and Taskforceâ2 and Frenockâ were applied on 10 March 2000. The difference between Taskforce 1 and 2 was that Taskforce 1 had 58.5% flupropanate and Taskforce 2 had 70%. Various rates of each herbicide were applied (Table 1) to compare their respective effectiveness. There were three replications of each treatment arranged in randomised blocks.

 

Table 1. Effect of herbicides on % brown out of serrated tussock measured on 23 May 2000 and % kill measured on 27 April 2001

 

Time of spraying in 2000	Herbicide	L/ha	kg a. i. /ha	Brown out                   (%)	Kill     (%)
11 February	Frenock	1.0	0.745	50	99.7
	(74.5% a. i.)	1.5	1.117	53	100
	Taskforce 1	1.0	0.585	47	100
	(58.5% a. i.)	1.25	0.731	53	100
		1.5	0.877	63	99.7
		1.75	1.024	57	100
		2.0	1.170	60	100
10 March	Frenock	1.0	0.745	57	100
	(74.5% a.i.)	1.5	1.117	53	100
	Taskforce	1.25	0.875	47	100
	(70% a. i.)	1.5	1.050	47	99.7
		1.75	1.225	53	100
		2.0	1.400	47	100
		3.0	2.100	60	100
	Nil	0.0	0.0	10	0

 

Observations

There was no difference between the various herbicide treatments as at 23 May 2000 and 27 April 2001. The brown out 3 and 4 months after the sprayings was quite advanced because it generally takes 3 months for the effects of flupropanate herbicides to be readily observable. This was because rainfall had been plentiful after the sprayings. Rainfall (mm/month) in the seven months after spraying on 11 February 2000 was 23, 92, 38, 29, 36, 18 and 35 mm; the respective rainfall after spraying on 10 March 2000 was 93, 44, 50, 70, 56, 112 and 24 mm.

 

All treatments had a high percentage kill of serrated tussock, the only living tussocks were near the edge of the plots which could have resulted from inaccurate spraying. The most remarkable feature of the kill was the high percentage at the low rates of 0.78, 0.98, 1.0, 1.17, 1.18 and 1.37 L/ha.