The Imtrader Ed.10 – Herbicide Efficacy on Pasture

In Corrigin, WA, a field trial was conducted between March and June 2017 to investigate the efficacy of post emergent herbicides on target weeds in a self-sown Serradella pasture.
The pest species present at the trial site were Mintweed (Salvia reflexa), Capeweed (Arctotheca calendula) and Wild turnip (Brassica tournefortii). The trial commenced in a self-sown Serradella paddock where a high weed burden was present, accounting for 90% ground coverage.
The trial was conducted in accordance with the principles of ANOVA, incorporating a Randomised Complete Block Design (RCBD) with 13 treatments and 3 replications, totalling 39 plots.
Treated plot size was 10 meters long by 2 meters wide, 0.5m buffers were utilised between plots.

The following treatments were evaluated:

Tmt Treatment description Formulation active Rate (/ha)
1 Untreated 0
2 Imtrade Amaze 700 Imazethapyr 70g
3 Imtrade Amaze 700 Imazethapyr 140g
4 Imtrade Edge 900 Propyzamide 550g
5 Imtrade Edge 900 Propyzamide 1100g
6 Imtrade Flumetsulam 800 Flumetsulam 25g
7 Imtrade Bromox 200 Bromoxynil 750mL
8 Imtrade Bromox 200 Bromoxynil 1500mL
9 Imtrade Cougar Bromoxynil / Diflufenican 500mL
10 Imtrade Cougar Bromoxynil / Diflufenican 1000mL
11 Buttress 2,4-DB 1000mL
12 Buttress 2,4-DB 3000mL
13 Imtrade Imazamox Imazamox 50g

RESULTS

Table 1; Comparison of treatment means. Mean phytotoxicity of Serradella (%)

No. Treatment Application rate 14 DAT 27 DAT
 (/ha) 6/04/2017 19/04/2017
1 Untreated 0 0         e 0 a
2 Imtrade Amaze 700 70g 5   bcde 0 a
3 Imtrade Amaze 700 140g 1.7       de 0 a
4 Imtrade Edge 900 550g 3.3     cde 0 a
5 Imtrade Edge 900 1100g 3.3     cde 0 a
6 Imtrade Flumetsulam 800 25g 3.3     cde 0 a
7 Imtrade Bromox 200 750mL 5   bcde 1.7 ab
8 Imtrade Bromox 200 1500mL 5   bcde 0 a
9 Imtrade Cougar 500mL 8.3   bcd 10     c
10 Imtrade Cougar 1000mL 16.7 a 16.7       d
11 Buttress 1000mL 10 abc 3.3 ab
12 Buttress 3000mL 8.3   bcd 6.7   bc
13 Imtrade Imazamox 50g 11.7 ab 1.7 ab
P value 0.006 <0.001
LSD 7.37 6.49

Means within the same cell with a letter in common are not significantly different (P>0.05)

All treatments caused some level of phytotoxicity to Serradella post application 14 DAT compared to the untreated control. All rates of Imtrade Cougar, Buttress and Imtrade Imazamox caused statistically more damage than the untreated control at 14 DAT. By 27 DAT, most treatments effects to the Serradella had reversed, with only Imtrade Cougar and the 3000mL/ha rate of Buttress exhibiting significant levels of damage.

WEED EFFICACY

Table 2; Comparison of treatment means. Mean brownout percent (%) of Mintweed

No. Treatment Application rate 14 DAT 27 DAT
 (g/ha) 6/04/2017 19/04/2017
1 Untreated 0 0           f 0           f
2 Imtrade Amaze 700 70 8.3     cdef 5         ef
3 Imtrade Amaze 700 140 6.7       def 6.7         ef
4 Imtrade Edge 900 550 3.3        ef 3.3         ef
5 Imtrade Edge 900 1100 3.3        ef 1.7         ef
6 Imtrade Flumetsulam 800 25 5        ef 0           f
7 Imtrade Bromox 200 750 20 abcde 20       d
8 Imtrade Bromox 200 1500 33.3 a 40     c
9 Imtrade Cougar 500 26.7 ab 43.3     c
10 Imtrade Cougar 1000 30 ab 56.7 ab
11 Buttress 1000 15   bcdef 46.7   bc
12 Buttress 3000 23.3 abcd 66.7 a
13 Imtrade Imazamox 50 25 abc 11.7       de
P value 0.005 <0.001
LSD 18.26 11.11

Means within the same cell with a letter in common are not significantly different (P>0.05)

Table 3; Comparison of treatment means. Mean brownout percent (%) of Capeweed

No. Treatment Application rate 14 DAT 27 DAT
 (g/ha) 6/04/2017 19/04/2017
1 Untreated 0 0         e 0                i
2 Imtrade Amaze 700 70 6.7     cde 5           fghi
3 Imtrade Amaze 700 140 5       de 3.3            ghi
4 Imtrade Edge 900 550 0         e 1.7              hi
5 Imtrade Edge 900 1100 0         e 1.7              hi
6 Imtrade Flumetsulam 800 25 5       de 6.7         efgh
7 Imtrade Bromox 200 750 10     cd 11.7     cde
8 Imtrade Bromox 200 1500 11.7     cd 13.3   bcd
9 Imtrade Cougar 500 23.3 ab 18.3 ab
10 Imtrade Cougar 1000 28.3 a 20 a
11 Buttress 1000 3.3       de 10      def
12 Buttress 3000 11.7     cd 16.7 abc
13 Imtrade Imazamox 50 15   bc 8.3      defg
P value <0.001 <0.001
LSD 8.64 5.34

Means within the same cell with a letter in common are not significantly different (P>0.05)

Table 4; Comparison of treatment means; Mean brownout percent (%) of Wild Turnip.

No. Treatment Application rate 14 DAT 27 DAT
 (g/ha) 6/04/2017 19/04/2017
1 Untreated 0 0       d 0           f
2 Imtrade Amaze 700 70 13.3     cd 18.3       de
3 Imtrade Amaze 700 140 16.7   bcd 26.7   bcde
4 Imtrade Edge 900 550 6.7     cd 20     cde
5 Imtrade Edge 900 1100 8.3     cd 13.3         ef
6 Imtrade Flumetsulam 800 25 13.3     cd 30   bcd
7 Imtrade Bromox 200 750 15   bcd 20     cde
8 Imtrade Bromox 200 1500 10     cd 20     cde
9 Imtrade Cougar 500 33.3   b 33.3   bc
10 Imtrade Cougar 1000 56.7 a 26.7   bcde
11 Buttress 1000 21.7   bc 38.3   b
12 Buttress 3000 60 a 60 a
13 Imtrade Imazamox 50 18.3   bcd 30   bcd
P value <0.001 <0.001
LSD 19.37 13.47

Means within the same cell with a letter in common are not significantly different (P>0.05)

Imtrade Bromox 200, Imtrade Cougar, Buttress and Imtrade Imazamox caused the most damage to target weeds. Wild Turnip was the most susceptible weed, being effected by most treatments during the trial. Overall, weed control was poor, with no treatment providing satisfactory control of the weed burden present. Imtrade Cougar and Buttress provided the best control out of the treatments tested, but also caused the most damage to the Serradella.

It is suspected that the environmental conditions experienced over the experimental period were responsible for the poor weed control experienced in this trial. The weeds self-sown Serradella had germinated on the back of a large rainfall event in February, following which they were exposed to the typical conditions normally experienced during summer, which are not generally conducive to weed growth. The weeds were tending towards the larger side of the possible control size with the chemistries applied, which in combination to the stressed nature of the plants may have contributed the poor result obtained in this situation. The trial is being replicated at a more typical application timing to see if the efficacy on target weeds improves under more favourable conditions.

  • Imtrade Cougar and Buttress can be damaging to self-sown Serradella when applied at the 6-8 leaf stage.
  • Weed control is poor with the post-emergent options available for use with Serradella under taxing summer conditions.

This trial indicates that it is probably not viable to salvage summer germinating self-sown Serradella for seed production when high weed burden is present.