Action: Apply herbicide and remove plants to control grass
- One randomized, replicated, controlled, paired study in the USA found that areas sprayed with herbicide and weeded to control non-native grass cover had higher cover of native grasses and forbs than areas that were not sprayed or weeded, but not a higher number of native plant species. The same study found that spraying with herbicide and weeding reduced non-native grass cover.
Combining the application of herbicide with removal of grass may help to reduce the abundance of problematic grass species, and thus help shrubland plants to increase in size and cover.
Supporting evidence from individual studies
A randomized, replicated, controlled, paired study in 2005–2008 in creosote bush shrubland invaded by non-native grasses in California, USA (Steers & Allen 2010) found that spraying with herbicide, followed by weeding, decreased invasive grass cover, increased the cover of native grass and forb species, but did not increase the number of annual plant species. Areas that were sprayed with herbicide and were weeded had lower non-native grass cover (0–38%) than areas that were not sprayed or weeded (40–65%). Also, areas that were sprayed with herbicide and weeded had lower had higher cover of native grass and forb species (20–87%) than areas that were not sprayed or weeded (13–36%). However, the number of native annual plants was not significantly different in areas that had been sprayed with herbicide and weeded (4–18%) and unsprayed and unweeded areas (23–37%). In January 2006 and 2008 twelve 8 m x 8 m plots were sprayed with the grass specific herbicide Fusilade-II and then weeded by hand while twelve other plots were not sprayed with herbicide or weeded. Plant cover was recorded in March-April 2006 and 2008 in 0.5 m2 quadrats located in each plot.