Comparison of the effects of the herbicides Taskforce® and Frenock® on mature serrated tussock growing in the field

Effects of Taskforceт and Frenockт on serrated tussock

Taskforceт and Frenockт) 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. Taskforceт1 and Frenockт were applied on 11 February 2000 and Taskforceт2 and Frenockт 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	аа L/ha	kg a. i. /ha	Brown outаааааааааааааааааа (%)ааа	ааа Kill ааа (%)
11 February	Frenock	аа 1.0	аа 0.745	аа 50	аааа 99.7
	(74.5% a. i.)	аа 1.5	аа 1.117аа	аа 53	аа 100
				аа
	Taskforce 1	аа 1.0	аа 0.585	аа 47	аа 100
	(58.5% a. i.)	аа 1.25	аа 0.731	аа 53	аа 100
		аа 1.5	аа 0.877	аа 63	аааа 99.7
		аа 1.75	аа 1.024	аа 57	аа 100
		аа 2.0	аа 1.170	аа 60	аа 100

10 March	Frenock	аа 1.0	аа 0.745	аа 57	аа 100
	(74.5% a.i.)	аа 1.5	аа 1.117	аа 53	аа 100
			а
	Taskforce	аа 1.25	аа 0.875	аа 47	аа 100
	(70% a. i.)	аа 1.5	аа 1.050	аа 47	аааа 99.7
		аа 1.75	аа 1.225	аа 53	аа 100
		аа 2.0	аа 1.400	аа 47	аа 100
		аа 3.0	аа 2.100	аа 60	аа 100

	Nil	аа 0.0	аа 0.0	аа 10	аааааа 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.