Evaluating practical macrophyte control tools on small agricultural waterways in Canterbury, New Zealand

Document Type

Article

Publication Date

4-3-2019

Publication Title

New Zealand Journal of Marine and Freshwater Research

Volume

53

Issue

2

First Page

182

Keywords

agricultural drains, agricultural waterways, aquatic weeds, Erythranthe guttata, Macrophyte control, Nasturtium microphyllum, plant management

Last Page

200

Abstract

Excessive macrophytes can cause significant problems in agricultural waterways requiring active management. Conventional control techniques can have a range of adverse effects. We investigated several control tools in two experiments: firstly, we tested eight treatments at a small-scale (2 m × 2 m). We found intensive hand weeding, weed mat and herbicide spraying to be effective treatments, reducing macrophyte cover to <5%. Hand weeding and weed mat immediately reduced cover, while dieback from herbicide took two months. Weed mat was a novel and effective control mechanism along stream banks. Secondly, we tested the impact of shading on macrophyte growth. Macrophyte growth was enhanced under partially shaded conditions, but with 80% effective shading over the entire channel, cover was reduced to 17%. Once treatments ceased, macrophytes grew back within 3–5 months. Long-term, control methods will require combinations of tools but will need to include optimal shading for the target species.

DOI

10.1080/00288330.2018.1487454

ISSN

00288330

E-ISSN

11758805

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