Non-target effects of grass-specific herbicides differ among species, chemicals and host plants in Euphydryas butterflies

Published source details Schultz C.B., Zemaitis J.L., Thomas C.C., Bowers M.D. & Crone E.E. (2016) Non-target effects of grass-specific herbicides differ among species, chemicals and host plants in Euphydryas butterflies. Journal of Insect Conservation, 20, 867-877.
Share Tweet Email

Actions

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, controlled study in 2013–2014 in a greenhouse in Washington, USA (Schultz et al. 2016) found that one of three herbicides commonly used to control invasive grasses reduced the survival of snowberry checkerspot Euphydryas colon caterpillars, but not Edith’s checkerspot Euphydryas editha colonia or Baltimore checkerspot Euphydryas phaeton caterpillars. The survival of snowberry checkerspot caterpillars sprayed with sethoxydom and NuFilm (78%) was lower than caterpillars sprayed with water (98%), but the survival of caterpillars sprayed with clethodim and NuFilm (85%), fluazifop-p-butyl and NuFilm (88%) or NuFilm alone (93%) was not significantly different from those sprayed with water. The survival of caterpillars sprayed with fluazifop-p-butyl and NuFilm (snowberry checkerspot: 51–89%; Edith’s checkerspot: 87–88%; Baltimore checkerspot: 91–95%) was not significantly lower than unsprayed caterpillars (snowberry: 55–92%; Edith’s: 84–92%; Baltimore: 96–98%). Eggs were collected from wild-caught females (snowberry and Edith’s checkerspot) or wild-laid egg clusters (Baltimore checkerspot), and caterpillars were reared on ribwort plantain Plantago lanceolata. In August 2014, forty snowberry checkerspot caterpillars were exposed to each of five treatments: one of three herbicides used regularly for prairie restoration (fluazifop-p-butyl, sethoxydim and clethodim) applied using their most common formulations (Fusilade DX^®, Poast^® and Envoy Plus^®, respectively) in combination with a “sticker-spreader” (adjuvant NuFilm IR^®); the NuFilm alone; or a water treatment (see paper for details). Caterpillars were kept in containers and fed fresh plantain exposed to the same treatment. In August–September 2013, caterpillars of three species were randomly assigned to two treatments, sprayed with Fusilade and NuFilm or unsprayed, and placed in groups of 20 in 5–6 host plant microcosms/treatment/species. In both experiments, survival to overwintering was recorded.

(Summarised by: Andrew Bladon)