Effect of Taskforceâ, compared to that of Frenockâ, 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: Frenockâ with 74.5% flupropanate; Taskforceâ1 with 58.5% a. i.; Taskforceâ2 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

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 Taskforceâ 1 and 2 had the same effects on the survival of seedlings of five plant species as Frenockâ.