Could herbicide used to control alien weeds be harming threatened New Zealand spiders?

The endangered spider Latrodectus katipo Powell, 1871 (Theridiidae) is restricted to coastal habitats around New Zealand, which are being invaded by lupins Lupinus aboreus Sims. We tested the effect of twoherbicides used to control lupins, Grazon (R) (triclopyr) and Versatill (R) (clopyralid) and the surfactant Boost (R) (dimethicone copolyol) on the survival of an exotic surrogate spider species Steotoda capensis (Theridiidae). The herbicides were tested at half and full application rates and caused no significant increase in mortality 7 days after treatment under laboratory conditions. However, the surfactant resulted in significantly higher spider mortality (c. 35%) compared with the other treatments. Recommendations were made to limit the use of surfactant when applying herbicide in situations where threatened invertebrate species may be present.