Estimated herbicide use in the commercial forest sector in South Africa

ABSTRACT

This paper examines herbicide use in South African commercial plantations in 2017/18 across three climate zones (cool temperate − CT, warm temperate − WT and subtropical − ST) for three genera (eucalypts, pines and acacias) grown for two end-products (sawn timber and pulpwood). Herbicide information was obtained from 46 timber plantations owned by six forestry companies, comprising 343 872 ha surveyed. The herbicide survey was divided into three climate zones due to increased vegetation growth (and hence more herbicide use) on more productive ST sites compared to moderately productive WT sites, with the lowest vegetation growth on CT sites (lower productivity). The survey was further divided into three distinct vegetation management phases associated with plantation forestry (pre-establishment, re-establishment and post-establishment) to compare herbicide use bet ween genera grown on an annual basis. A total of 188 288 kg (or 0.55 kg ha⁻¹) of herbicide active ingredient (a.i.) was applied in the area surveyed. Glyphosate-based products accounted for 97% of all the herbicides applied, and metazachlor and triclopyr butoxy ethyl ester accounted for 2%. Overall, herbicide use per hectare on an annual basis was highest in the ST zone, followed by the WT and CT zones. For both the CT and WT zones, the general trend was that the pre-establishment phase received noticeably more herbicides, followed by the re- and post-establishment phases (pre$>$re$>$post). This trend remained similar for the genera grown (pre$>$re$>$post), with hardwoods receiving more herbicides than softwoods. In contrast, there was little difference in herbicide use between the re- and pre-establishment phases for the ST zone, with the post-establishment phase being noticeably less. Besides providing benchmark data related to herbicide use in South African plantations, future research should investigate the potential for a reduction in herbicide use in those regions, vegetation management phases and management regimes where it is highest.

KEYWORDS:

• vegetation management
• glyphosate
• timber plantations
• herbicide survey

Acknowledgements

The authors express their appreciation to the sponsors of this research (Forestry South Africa and Nelson Mandela University) and the forestry industry, which provided valuable information on their herbicide use. We thank two anonymous reviewers for their valuable comments on earlier drafts, which helped improve the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Forestry South Africa; Nelson Mandela University (Postgraduate Research Scholarship).