Full Length Research Paper

The efficacy and safety of bromacil based herbicide for the control of the invasive bush species in South African rangelands

S. Dube¹*, M. S. Lesoli¹ and A. O. Fatunbi²

¹Livestock and Pasture Science Department, University of Fort Hare, PB x 1314, Alice 5700, EC, South Africa.

²Agricultural and Rural Development Research Institute (ARDRI), University of Fort Hare, PB x 1314, Alice 5700, EC, South Africa.

*Corresponding author. E-mail: sdube@ufh.ac.za.

Accepted 3 February, 2009

The use of bromacil based herbicides in agriculture and environmental management is a growing practice with economic importance. Bromacil possesses broad toxicity to many plant species, although, different formulations exist that are used for different purposes in farming systems. There is increasing concern about its use for the control of invasive woody species on South African rangelands; especially its effects on non-target grasses, broad leaved plants and other biotic components of the rangeland ecosystem. This review outlines the importance of bromacil use, its nature and activities as an ingredient in herbicide formulation and the effects of its use on biotic and non-biotic components of rangeland ecosystems. The current use of bromacil based herbicides for the control of bush encroachment seems necessary to derive good productivity from encroached rangelands and reduce cost and drudgery associated with other methods of bush control. Bromacil is absorbed through the plant’s root system and translocated upwards via the xylem vessels to the leaves, where it interferes with light harvesting complexes and disrupt the photosynthetic pathways of the plant. This kills the plant slowly; sometimes, it spans over two years. Bromacil could be persistent in the environment for the same length of time, depending on the application method, the target species and the soil properties at the application site. Bromacil has a very low mammalian toxicity, but is considered to be slightly toxic to fishes and amphibians. The effect of Bromacil on soil microbial population depends on the exact formulation, concentration and microbial species in question. Yet, bromacil is degraded by microorganisms in the soil and water, portions that escape into open water bodies are also degraded by photo-oxidation reaction. While bromacil provides for sustained weed control, its persistence in the environment and low degradation rates, is a cause for concern.

Key words: Bromacil, invasive species, rangeland encroachment.