APVMA Approval Number: 53015/0700

Effect of Taskforce®, compared to that of Frenock®, on the survival of five plant species in the 93 days after sowing

Three flupropanate herbicides were applied to steam sterilized chernozem soil on 7 March 2000 and seeds of five plant species (Table 1) sown two hours later. The soil was in 28 x 32 x 4 cm flats lined with plastic to stop leaching of herbicides. Twenty seeds of serrated tussock, Sirosa phalaris, Currie cocksfoot, Aurora lucerne and Denmark subterranean clover were sown in rows in each flat 0.5 cm deep and covered with the soil present in the flat. The herbicides were: Frenock® with 74.5% flupropanate; Taskforce®1 with 58.5% a. i.; Taskforce®2 with 70% a. i.; and a nil control. The flats were placed in a glasshouse at 200C and hand watered. Emergence and survival of the plants was measured at approximately 15-day intervals for 93 days to record living and dead plants as well as plant health. There were three replications of each treatment arranged in randomised blocks with the species randomised within each flat.

Results

Seedlings of all species emerged from the soil but growth was restricted by the herbicides. Grass shoots only emerged 1 to 2 mm before symptoms of herbicide toxicity were evident but legumes produced cotyledons and the seedleaf before symptoms appeared. Most grass seedlings with severe symptoms died in the 93 days of the trial. Those with minor symptoms recovered. Legume seedlings exhibited the typical anamorphosis caused by flupropanate where leaves were folded or rolled into small balls. Legume seedlings remained affected until the end of the trial (Table 1).

   The survival of serrated tussock and phalaris seedlings after 93 days was lower (P<0.05) on all herbicide treatments than on the control; the survival of cocksfoot was lower (P<0.05) on all herbicide treatments, except one, than on the control (Table 1). For subterranean clover there was no difference between survival on the control and on the herbicide treatments and for lucerne survival on only one herbicide treatment was lower than the control (Table 1). The difference in survival of legumes between the control and the herbicide treatments was not as great as for the grasses, but by day 93, most legumes on the herbicide treatments were sick with the potential to die (Table 1).

   Survival of cocksfoot appeared higher on all herbicide treatments than that of serrated tussock and phalaris (Table 1). Survival of grasses declined with increasing rate of herbicide.

Table 1. Effect of three flupropanate herbicides on the survival and health of seedlings 93 days after sowing

Herbicide

Rate

Tuss

Phal

Cock

Lucerne

Sub clover

 

L/ha

kg a i /ha

% S

% S

% S

% S

% H

% S

% H

Frenock

0.5

0.372

32bA

38b

73ab

38ab

2

72a

8

 

1.0

0.745

15b

15cd

48c

32ab

0

63a

5

Taskforce 1

1.0

0.585

27b

18bcd

60bc

40ab

0

42a

0

Taskforce 2

0.5

0.350

35b

30bc

58bc

47a

5

62a

2

 

1.0

0.700

25b

20bcd

45c

40ab

2

63a

0

 

1.5

1.050

8b

3d

18d

28b

0

55a

0

Nil

0.0

0.0

77a

67a

85a

47a

100

68a

100

Tuss, Serrated tussock; Phal, Phalaris; Cock, Cocksfoot;

% S: Survival expressed as a percentage of the seed sown.

% H: % of plants healthy 93 days after sowing seed.

AValues in columns not followed by a common letter differ significantly at P<0.05.

There was no difference (P<0.05) between the effects of the three herbicides on survival of seedlings (Table 1).

Conclusions

At equivalent rates, the two new flupropanate preparations Taskforce® 1 and 2 had the same effects on the survival of seedlings of five plant species as Frenock®.