Controlling Woody Weed Chinese Elm (Celtis sinensis Pers.) with Stem-Implanted Herbicide Capsules.

Ciara Jade O’Brien,Victor Joseph Galea,Vincent Mellor

doi:10.3390/plants11030444

Ciara Jade O’Brien, Victor Joseph Galea + Show 1 more

Open Access

https://doi.org/10.3390/plants11030444

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Abstract

Chinese elm [Celtis sinensis Pers.] is an emerging environmental weed naturalised throughout the coastal and riparian (creek-banks, river margins, and streams) regions of eastern Australia. Throughout this introduced range, its management is limited to the application of synthetic herbicides and mechanical clearing operations (terrain and soil type permitting). The current mechanisms of chemical control (basal bark spraying, stem-injection, and cut-stump applications) often result in collateral damage to non-target native species (such as Eucalyptus spp. and Casuarina cunninghamiana Miq.) through herbicidal drift, runoff or leaching into adjacent habitats. This has raised concerns regarding the suitability of synthetic herbicides in ecologically sensitive (e.g., riparian zones, rainforest margins, and woodlands) or low-value habitats, thereby promoting significant developments in the fields of integrated weed management. This study investigated the effectiveness of a novel stem-implantation system for controlling woody weed species in the context of a conserved habitat. A replicated trial (n = 315) was established among a naturally occurring population of C. sinensis. This trial involved the mapping, measurement, and treatment of this invasive species with five encapsulated synthetic herbicides, as well as an untreated control and benchmark treatment (diesel + AccessTM). A significant effect (p < 0.05) on plant vigour and functional canopy was discerned for each assessment period following trial establishment. The highest incidence of mortality was observed among the individuals treated with glyphosate (245 mg/capsule), aminopyralid and metsulfuron-methyl (58.1 and 37.5 mg/capsule) and picloram (10 mg/capsule), achieving a similar response to the basal bark application of diesel and AccessTM (240 g/L triclopyr, 120 g/L picloram, and 389 g/L liquid hydrocarbon). This was also evidenced by a rapid reduction in functional canopy (i.e., no or little living leaf tissue) from three weeks after treatment. Unlike their industry counterparts, these encapsulated herbicides are immediately sealed into the vascular system of the target species by a plug. This significantly minimises the possibility of environmental or operator exposure to synthetic compounds by providing a targeted, readily calibrated herbicide application.

Highlights

Chinese elm (Celtis sinensis Pers.) is a deciduous or semi-deciduous tree native to the slopes of eastern Asia, most notably China, Korea, Taiwan and Japan [1,2]
Rat-Kangaroo Aepyprymnus rufescens, and Black Wallaby Wallabia bicolor) by altering habitat conditions or resource availability [1,4,5,6]. It has formed dense infestations in disturbed sites such as urbanised bushlands, parklands and roadsides [1,3]. Given this evidence of invasiveness, C. sinensis is ranked in the ten highest invasive species in south-east Queensland alongside other notable woody weeds such as Lantana (Lantana camara var. camara), Camphor Laurel (Cinnamomum camphora) and Broad-Leaf Pepper Tree (Schinus terebinthifolius) [7]
This study investigated the effectiveness of BioHerbicides Australia’s proprietary stem-implantation system (InJecta 800®) and Di-Bak® range of synthetic herbicides for controlling C. sinensis in the context of a conserved habitat

Summary

Introduction

Chinese elm (Celtis sinensis Pers.) is a deciduous or semi-deciduous tree native to the slopes of eastern Asia, most notably China, Korea, Taiwan and Japan [1,2] This species has spread from its endemic habitat to the coastal and sub-coastal regions of Australia, New Zealand and South Africa through its deliberate introduction as an ornamental plant [2]. Rat-Kangaroo Aepyprymnus rufescens, and Black Wallaby Wallabia bicolor) by altering habitat conditions or resource availability (foliage, seeds, nectar, or sap) [1,4,5,6] It has formed dense infestations in disturbed sites such as urbanised bushlands, parklands and roadsides [1,3]. Given this evidence of invasiveness, C. sinensis is ranked in the ten highest invasive species in south-east Queensland alongside other notable woody weeds such as Lantana (Lantana camara var. camara), Camphor Laurel (Cinnamomum camphora) and Broad-Leaf Pepper Tree (Schinus terebinthifolius) [7]

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