Nature’s Tiny Heroes: Using Biocontrol to Fight Invasive Species in the Western Cape

In the biodiverse landscapes of the Western Cape, a quiet but critical battle is underway. Invasive alien plants are spreading rapidly, crowding out native fynbos, stealing water from already-stressed ecosystems, and increasing the risk of destructive wildfires. Invaders like Port Jackson willow (Acacia saligna), hakea (Hakea sericea), black wattle (Acacia mearnsii) and lantana (Lantana camara) are not only difficult to control—they are deeply harmful to South Africa’s ecosystems. They displace native species, reduce biodiversity, and degrade both soil and water resources.
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To win this battle, we need every tool at our disposal. At the Grootvadersbosch Conservancy (GVBC), we’re working with partners to combine mechanical and chemical control methods with innovative, nature-based solutions—specifically, biological control.

​GVBC is collaborating with leading researchers from institutions such as the Agricultural Research Council (ARC), the Centre for Biological Control at Rhodes University, and the University of Cape Town to promote and distribute biological control agents—specialist insects and mites that target invasive plants without harming native species. These tiny organisms are highly specific to their host plants, making them powerful allies in long-term ecological restoration. By harnessing their natural behaviours, biocontrol transforms scientific research into tangible on-the-ground results.

Meet some of the heros

• Seed-devouring weevils: These insects can destroy up to 90% of hakea seeds, greatly limiting the plant’s ability to spread.
• Leaf-munching moths: Their caterpillars feed on Port Jackson willow leaves, weakening the plant and reducing its ability to photosynthesize.
• Gall-forming mites (Aceria lantana): Introduced to control Lantana camara, these microscopic mites induce gall formation in plant tissues, which stunts growth and suppresses flowering

Each of these agents plays a targeted role in weakening invasive plant populations and helping restore the balance of native ecosystems.

Learn More About Other Biocontrol Agents
GVBC recently hosted a training workshop with Dr Fiona Impson, where she introduced the key biological control agents used in the Western Cape and demonstrated how to help capture and distribute them.

​You can watch the training on our YouTube channel.

The Growing Threat of New Invasive Plants: Lantana camara

Lantana camara is emerging as a significant threat in our area. This thorny, fast-growing shrub forms dense thickets that shade out indigenous plants and block wildlife movement. It’s toxic to some livestock and wildlife, and its colourful berries allow it to spread rapidly via birds and mammals.
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Manual removal is extremely labour-intensive, and chemical treatment is both costly and unsustainable. While lantana was historically more common in the eastern parts of the country, it is now spreading rapidly in the Western Cape—possibly due to shifting climate and weather patterns. With the help of Dr Fiona Impson and Dr Alan Wood, GVBC recently released a biological control agent to combat this tough invader.
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Aceria lantana: A Microscopic Marvel
Aceria lantana is a species of gall-forming mite, carefully selected and tested by biocontrol scientists to specifically target Lantana camara. These mites are host-specific, meaning they pose no threat to other plants, animals, or people. Once introduced into the environment, they settle on the leaves and stems of lantana plants and begin feeding.
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What makes them especially effective is their ability to disrupt plant growth. As they feed, the mites induce the formation of tiny galls—swollen, abnormal tissues—that interfere with nutrient flow, inhibit flowering, and reduce the plant’s ability to reproduce and spread. Over time, repeated mite activity leads to a noticeable decline in lantana’s density and vigour. GVBC recently released Aceria lantana in a test area. Unfortunately initial results do not look as effective as hoped but more releases are planned to increase the potentail impact and spread. 

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How You Can Help
Biocontrol is a powerful conservation tool—but it’s even more effective with community support. Here’s how you can get involved:

• Report invaders: If you spot Port Jackson, wattle, hakea, or lantana, snap a photo and post it on iNaturalist.
• Volunteer: Join a planting day or help out during a biocontrol release event.
• Share the story: Spread the word about these microscopic defenders and the important role they play in restoring ecosystems.
• Join the discussion: Participate in future discussions as part of the Silver Mountain music festival on 16th June. Get your tickets now to attend in person or register now to join the discussion on Zoom. 

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​GVBC’s work is driven by partnerships and community action. Learn more about biocontrol, support ongoing research, or get involved by visiting the GVBC website. Together with ARC, Rhodes University, and a network of passionate conservationists, we’re showing that sometimes the smallest heroes can make the biggest impact.