| Researcher(s) |
Linda Bailey |
|---|---|
| Year(s) | 2022 |
| Contributor | Northern Grower Alliance |
| Trial location(s) |
Felton, QLD
|
To evaluate residual control of common sowthistle in fallow
This trial was established to evaluate residual common sowthistle control in fallow. Treatments were applied in early January 2022 to a paddock cropped to wheat in 2021. The site had ~10-20 cm tall wheat stubble with ~100% ground cover. The site received a commercial fallow knockdown spray ~2 weeks prior to the residual herbicide application.
The site received ~21 mm at 7 days after application (7 DAA) and a total of ~520 mm over the duration of the trial. Weed counts were conducted at 19 DAA, 55 DAA and 91 DAA. Data from the 19 DAA assessment was ignored as there were a small number of 6-9 leaf common sowthistle. These weeds would have been emerged at the time of residual herbicide application but covered by the dense groundcover. A commercial fallow double knock was applied on 33 and 39 DAA to control weeds that had emerged prior to the residual herbicide application. In the two weeks following the double knock application ~230 mm of rainfall was recorded.
Residual control was assessed at 55 DAA with untreated common sowthistle populations of ~2.1/m2 at the cotyledon to 2 leaf stage. Residual control >90% was achieved from all treatments containing Valor, both rates of Voraxor, Tordon 75-D, Terbyne Xtreme and an experimental Group 14 herbicide despite ~290 mm of rainfall since application. Common sowthistle counts in the Balance, Dual Gold alone, Gesaprim and experimental Group 27 herbicide treatments were not significantly different to those in the untreated.
In the following five weeks, an additional 230 mm of rainfall was received. Assessment at 91 DAA found common sowthistle at three distinct growth stages. The largest were at stem elongation and expected to be primarily the seedlings assessed at 55 DAA. Similar treatment patterns were observed to the 55 DAA assessment.
Rosette staged common sowthistle at ~15-20 cm diameter were present at ~3.3/m2 in the untreated. These weeds are likely to have emerged from rain events between 50-59 DAA when a total of ~95 mm of rainfall was recorded. The most effective control (~80-90%) was obtained from all treatments containing Valor or the experimental Group 14 herbicide.
Seedling staged common sowthistle at 2-3 leaf were present at ~0.6/m2 in the untreated. These weeds are likely to have emerged from rain events between 75-82 DAA when a total of ~187 mm of rainfall was recorded. No treatment provided significant control, however the lowest weed counts were present where Valor or the experimental Group 14 herbicide were applied.
In this situation all treatments containing Valor (alone or in mixture), Voraxor, Tordon 75-D, Terbyne Xtreme and an experimental Group 14 herbicide all provided good levels of residual common sowthistle control (90-100%), up to ~55 days after application with ~290 mm of rainfall. Valor, and the experimental Group 14 herbicide provided longer residual control under the high rainfall conditions but did not effectively control an emergence that occurred ~80 days after application following >330 mm of rainfall. Balance and Dual Gold provided poor levels of weed suppression under the high rainfall conditions.
| Lead research organisation |
Northern Grower Alliance |
|---|---|
| Host research organisation | N/A |
| Trial funding source | GRDC NGA2009-002RTX |
| Related program | N/A |
| Acknowledgments | N/A |
| Other trial partners | Not specified |
| Crop type | None: No crop specified |
|---|---|
| Treatment type(s) |
|
| Trial type | Experimental |
| Trial design | Replicated |
| Sow date | Not specified |
|---|---|
| Harvest date | Not specified |
| Plot size | Not specified |
| Plot replication | Not specified |
SILO weather estimates sourced from https://www.longpaddock.qld.gov.au/silo/
Jeffrey, S.J., Carter, J.O., Moodie, K.B. and Beswick, A.R. (2001). Using spatial interpolation to construct a comprehensive archive of Australian climate data , Environmental Modelling and Software, Vol 16/4, pp 309-330. DOI: 10.1016/S1364-8152(01)00008-1.
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