Characterizing a contentious management tool: The effects of a grass-specific herbicide on the silvery blue butterfly

Published source details Glaeser R.M. & Schultz C.B. (2014) Characterizing a contentious management tool: The effects of a grass-specific herbicide on the silvery blue butterfly. Journal of Insect Conservation, 18, 1047-1058.
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This study is summarised as evidence for the following.

	Action	Category
	Remove or control non-native or problematic plants Action Link

Remove or control non-native or problematic plants

A replicated, randomized, paired, controlled study in 2013 in an upland prairie in Oregon, USA (Glaeser & Schultz 2014) found that applying herbicide to control invasive grasses in the early spring did not increase use of the habitat by Columbia silvery blue butterflies Glaucopsyche lygdamus columbia, or the number or survival of eggs or caterpillars. In sprayed plots, the number of butterfly visits (12 individuals/plot), the time spent in the plot (34–154 seconds/visit), and the proportion of butterflies which landed (18–73%) did not differ significantly from unsprayed plots (visits: 10 individuals/plot; time: 40–98 seconds/visit; landed: 16–67%). Similarly, in sprayed plots, the number of eggs (3.9/subplot), caterpillars (1.3/subplot) and survival of eggs to large caterpillars (15%) did not differ significantly from unsprayed plots (eggs: 4.1/subplot; caterpillars: 1.3/subplot; survival: 14%). In March 2013, thirty-two plots (20 × 20 m) were paired based on equal host plant (Kincaid’s lupine Lupinus oreganus) cover (>15 m²/plot). In each pair, one plot was randomly assigned to the herbicide treatment (sprayed in March with 326 g/ha Fusilade DX® grass-specific herbicide and 425 g/ha Nufilm®) and the other was left unsprayed. In May 2013, the time spent in each plot by adult butterflies, and whether or not they landed, was recorded during 15-minute observations in 30 plots. From late April 2013, hatched and unhatched eggs were counted five times, and the number and size of caterpillars was counted eight times, at 4–5 day intervals in each of three 60 × 60 cm subplots/plot, centred on randomly selected flowering lupines.

(Summarised by: Andrew Bladon)