Pre-emergence control of threespike goosegrass is the best approach. Since goosegrass can emerge from April through August, a long persisting pre-emergence herbicide is needed. Alion is a new herbicide with more persistent weed control, which we are currently testing for April through August threespike goosegrass control. Alion can only be used after an almond orchard is a minimum of one year old.
As can be seen in the following table, even high rates of glyphosate poorly controlled threespike goosegrass. The addition of Sylgard 309 improved the control with glyphosate.
Poast at 40 oz/A plus WeatherMax at 44 oz/A controlled threespike goosegrass very well. Poast is an expensive treatment, but may only be needed as a spot treatment if pre-emergence herbicides are used effectively.
All treatments were applied October 2, 2009 to four replications and two inches of rain occurred 11 days later. Be sure to notice the control treatment included WeatherMax at 44 oz/A.
There were three Rely and three Poast (24 oz/A) treatments because sequential treatments were planned, but there wasn’t enough regrowth of the warm season perennial weed to allow for sequential treatments. This gives an unusual opportunity to see how much variability occurs with four replications at one location. The most accurate ratings are the ones at the bottom of the table where all identical or similar treatments are averaged together. Another trial was done in 2011 using these herbicides on threespike goosegrass with similar results.
| Threespike Goosegrass (0 to 10, for 0 to 100 % control) |
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| Herbicide Treatment | 3-Nov | 30-Nov | 1-Mar | 30-Mar | 21-May |
| Rely--115 oz/A* | 10.0 | 10.0 | 10.0 | 9.4 | 8.8 |
| Rely--115 oz/A* | 9.8 | 10.0 | 9.8 | 9.1 | 7.5 |
| Rely--115 oz/A* | 9.5 | 9.8 | 9.8 | 9.3 | 8.3 |
| Poast--24 oz/A + MSO--24 oz/A* | 8.0 | 9.8 | 9.5 | 9.0 | 9.0 |
| Poast--24 oz/A + MSO--24 oz/A* | 9.5 | 10.0 | 9.8 | 10.0 | 9.3 |
| Poast--24 oz/A + MSO--24 oz/A* | 9.8 | 9.8 | 9.8 | 9.5 | 9.3 |
| Poast--40 oz/A + MSO--32 oz/A + Trifol--1 pt/100 gal + Cayuse Plus--64 oz/A* | 10.0 | 10.0 | 10.0 | 10.0 | 9.8 |
| WeatherMax--66 oz/A* | 7.8 | 8.8 | 9.0 | 6.0 | 4.3 |
| WeatherMax--66 oz/A + Sylgard 309--16 oz/100 gal* | 9.3 | 9.8 | 9.3 | 8.0 | 6.8 |
| Control (WeatherMax--44 oz/A)* | 2.8 | 0.0 | 10.0 | 8.0 | 4.5 |
| All Rely | 9.8 | 9.9 | 9.8 | 9.3 | 8.2 |
| All Poast | 9.3 | 9.9 | 9.8 | 9.6 | 9.3 |
| All WeatherMax | 6.6 | 6.2 | 9.4 | 7.3 | 5.2 |
*All Rely and Poast treatments included WeatherMax at 44 oz/A and all treatments also included Prowl at 128 oz/A plus Goal at 10 oz/A