BBC Gardeners’ World Magazine Podcast · Immediate Media

Plant health matters, with Tracy Wilson

December 9, 2025·40 min·3 clips

Xylella disease strangles plants by blocking their sap flow, starting with the extremities and slowly killing them.

This episode focuses on plant biosecurity and the role gardeners play in preventing the spread of pests and diseases. Host Oliver Parsons is joined by Tracy Wilson MBE, a plant health expert from the UK government's Animal and Plant Health Agency. Wilson explains that biosecurity involves protecting gardens and the wider environment from non-native pests and diseases that arrive through trade or travel. The conversation covers specific threats like Xylella, a bacterium that blocks sap flow in plants like olives and rosemary and is established in parts of Europe. Wilson details the Colorado potato beetle, a striped pest whose first UK outbreak in 50 years was found in Kent in 2023, leading to export bans and intensive surveillance. She mentions the Asian longhorn beetle, an outbreak of which required the felling of over 2,000 trees and an eight-year control program costing over £2 million. Other discussed problems include Phytophthora ramorum, known as sudden oak death, and the invasive Spanish slug. Wilson explains the UK monitors around 1,400 different quarantine pests and diseases, with about 10-12 new non-native species establishing each year. She describes the plant passport system, which provides traceability for plants moved within the UK, like olive trees imported from abroad. The agency conducts non-symptomatic testing for threats like Xylella, sampling entire batches of plants like lavender even when they appear healthy. Wilson emphasizes that climate change and milder winters are increasing the risk that new pests could establish in the UK. A surprising insight is that inspectors sometimes find Colorado beetles in imported frozen peas or on leafy vegetables at airports. Wilson advises gardeners to avoid bringing plants or seeds back from holiday, as suitcases left open outdoors can attract hitchhiking pests like Asian hornets. She recommends a simple six-week quarantine for new plants in a domestic setting to monitor for hidden problems. The public is encouraged to report unusual sightings using tools like iNaturalist, with Wilson stating she would prefer a hundred false alarms over missing one genuine threat. The tone is educational and conversational, blending practical gardening advice with explanations of government policy and scientific concepts. The style is supportive, positioning gardeners as crucial partners in national biosecurity efforts. This episode is ideal for gardeners seeking to understand their role in ecosystem protection and those interested in the intersection of horticulture and environmental policy. Listeners looking for purely practical planting tips or light entertainment might find the regulatory detail less engaging.

As heard by us

A clear, practical look at the small signs that can protect whole gardens.

Plant biosecurity sounds technical on paper, but this episode keeps pulling it back to ordinary garden life. Tracey Wilson explains why curled leaves, holes, or an unfamiliar insect can matter for gardens, the countryside, and the plants and wildlife people care about.

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Why you'd press play

When a healthy plant suddenly looks off, this gives you what to notice before trouble spreads.

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