Using fire and herbicide to manage Campuloclinium macrocephalum (pompom weed)

Abstract

Campuloclinium macrocephalum (Less.) DC. is an invasive perennial herb native to South America, commonly known as pompom weed in South Africa. Anecdotal evidence suggests that fire reduces the seedbank of pompom weed without substantial impact on weed density, while herbicides primarily affect mature plants, suggesting the need for a more integrated control management approach. This study assessed the interactive effect of fire and herbicide for two growing seasons on pompom weed flowering, emerging seedlings, resprouting/regrowth of mature plants and density. During the initial growth period in 2020, fire alone substantially decreased the seedbank by more than 85%, without reducing the density of mature plants. Herbicide application in December 2020 following fire led to reduction of over 98% in mature plants during the same growing season. However, in the subsequent growing season of 2021, there was a 9% regrowth of mature plants in areas previously treated with fire and herbicide, necessitating an additional herbicide application. Vegetation structure was also found to significantly influence the growth of pompom weed, emphasising the importance of incorporating vegetation context into management planning. Integrating both fire and herbicide is recommended as an enhanced management strategy for controlling pompom weed.