Seed Head Suppression Trials

Bahia grass (Paspalum notatum) poses a significant challenge for vegetation managers throughout South East Queensland. To explore the best ways in which to suppress the seed-head production of this problem weed, the Integrated Vegetation Management Project (IVMP) is conducting a 12 week trial. At the beginning of this trial, a single application of various herbicides and plant growth regulators was applied to duplicated trial plots. Untreated plots and monthly mown plots were also set up for comparison. After 6 weeks, the interim results already show some promising management options.

Overall, most of the treatments are still performing well 6 weeks after application. All 12 of the chemical treatments equalled or outperformed the mown treatment in reducing the number and height of seed-heads produced. This result is surprising considering the chemical treatments had not been mown for about 6 weeks, while the mown treatment had been mown less than two weeks ago!

Treatment plots

No seed-heads have yet been produced in the plots for the best performing treatments, i.e. 100% seed-head reduction at this stage. Most treatments trialled have provided ¡Ý 90% reduction in seed-heads thus far.

As one might expect, the effects of the treatments on seed-head height are very similar. Average seed-head height in the control plots was 43cm while the height was already up to 37cm in the recently mown plots. The worst-performing treatments had an average seed-head height of 29.5cm, while the few seed-heads produced in the most promising plots had an average height of only 7cm.

Promising results

The effect of the treatments on sward height was also relatively similar. Average sward height in the control was about 11cm, while it was 8.5cm in the recently mown plots. The best performing plots had sward heights of 6-7cm, with most other treatments having sward heights of 7-8cm.

These results are suggesting that, in order to keep Bahia grass green and suppress its seed-head production, a number of the treatments being trialled are effective. It is also clear that a number of the treatments will be effective should your aim be to transition out the Bahia grass in an area under management.

Read the 9 week results here.

Back to news