Trialling tools using hand-weeding, weed mat and artificial shading to control nuisance macrophyte growth at multiple scales in small agricultural waterways

Document Type

Article

Publication Date

7-2-2020

Publication Title

New Zealand Journal of Marine and Freshwater Research

Volume

54

Issue

3

First Page

512

Keywords

agricultural waterways, aquatic weeds, Erythranthe guttata, Macrophyte control, Nasturtium microphyllum, restoration tools

Last Page

526

Abstract

Introduced aquatic macrophytes can dominate small agricultural waterways in summer and autumn becoming a significant management problem. Excessive growth can clog waterways, causing drainage issues and reducing agricultural productivity while in-stream velocities are reduced and sedimentation increased. Consequently, water managers remove them by mechanical clearance, chemical spray and cutting which can be costly and have negative impacts on in-stream habitat and ecological health. We trialled three tools to reduce macrophytes: hand-weeding, weed mat and artificial shading, at a reach-scale (50 m) and larger-scale (200–400 m). Hand-weeding reduced cover in the short-term, however macrophytes recovered to pre-treatment levels within one season. Weed mat along the banks was effective at reducing emergent macrophytes, particularly Erythranthe guttata (monkey musk) and Nasturtium microphyllum (watercress). Weed mat lasted for several growing seasons and continued to be effective. Shading over the waterway using polythene markedly reduced submerged macrophytes indicating that heavy shading by riparian plantings could reduce submerged macrophytes in the longer-term. These results indicate that in the short-term, weed mat could be used to limit sprawling emergent macrophytes. In the longer-term, weed mat used in conjunction with riparian planting could provide shading so that macrophyte cover in these small waterways could be reduced and controlled.

DOI

10.1080/00288330.2020.1722185

ISSN

00288330

E-ISSN

11758805

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