Effects of asulam spraying on non-target ferns

J. K. Rowntree, E. Sheffield

    Research output: Contribution to journalArticlepeer-review


    The systemic herbicide asulam is used extensively to control the weedy fern bracken (Pteridium aquilinum (L.) Kuhn). Other ferns were thought to be highly sensitive to asulam exposure, but there has been a dearth of experimental evidence. Eight fern species were exposed to asulam spray at three different application rates or a control of water. Asulam was applied at the recommended field application rate for bracken clearance, and at two further rates corresponding to 10 and 50 m downwind of an aerial spray event. Damage was assessed over two seasons. All ferns tested were severely damaged by exposure to the highest application rate, but sensitivity varied between species. Maximum damage occurred 1 year after spraying, and limited signs of recovery could be seen by the second season. The effects of adding the adjuvant Agral® to applications of asulam were tested on the threatened pteridophyte Pilularia globulifera L. No damage additional to that caused by exposure to asulam was observed. This work supports the view that 50 m buffer zones are sufficient to protect sensitive ferns from the effects of aerial spraying with asulam, provided that drift-reducing nozzles are used and the manufacturer's application guidelines are observed. © 2005 NRC.
    Original languageEnglish
    Pages (from-to)1622-1629
    Number of pages7
    JournalCanadian Journal of Botany
    Issue number12
    Publication statusPublished - Dec 2005


    • Adjuvant
    • Herbicide
    • Non-target
    • Nondestructive monitoring
    • Vegetation management


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