consumption on a small scale . Species that fall into this category , are usually considered ‘ industry species ’, which have both positive and negative consequences for the economy , however , there are inevitable conflicts of interest that arise between those wanting to control or eradicate the plants due to their negative environmental impacts and those wanting to maintain and develop them for commercial gain .
In South Africa the preferred method of controlling invasive trees that are potential conflict species , is by using biocontrol agents that reduce the reproductive output of the host plants . Agents that target the buds , flowers and / or seeds are often the focus for research endeavours to manage the spread of such species . By utilising these methods of control , annual seed production can be
Damage by stem boring weevil – Sesbania
limited , thus reducing both numbers of seed for spread and further accumulation of seed in the soil , but at the same time , adult trees remain in the system and can continue to be utilised for their commercial and social benefits . Notably , South Africa was the first country globally , to initiate a biocontrol programme against an invasive tree , using a seed-feeding insect , when a seed weevil was released against Hakea sericea in 1970 . Subsequently , the investigation into agents which limit reproductive-potential for tree species has expanded , with a total 20 species of invasive trees currently being managed in this manner with varying degrees of success .
The process to initiate a biocontrol programme against any species , but specifically a ‘ conflict-of-interest ’ species , is a time-consuming one . Besides the ecological studies to establish whether the selected agents are suitably host specific , and the best option for the target weed ; open communication and discussions are required at various levels of stakeholder engagement , including government , managers , researchers , farmers and industry to avoid controversy .
In short , biocontrol of invasive trees can be successful if integrated correctly with other management strategies , and if all stakeholders ’ opinions and concerns are given due credit . The importance of industry species is undisputable , but so too is the conservation of natural resources such as biodiversity . Thus , finding the delicate balance between these concerns requires consideration of all affected parties , and , although there are always several avenues to consider when initiating such a biocontrol programme , South Africa has experienced a great deal of success on this front .
Seed-feeding weevil on black wattle
AgriKultuur | AgriCulture
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