According to Dr Milad Rashidifard, a senior lecturer in the Department of Zoology and Entomology at the University of the Free State (UFS), these microscopic organisms can cause yield losses of between 10% and 30%. In extreme cases, without any management strategies, losses can reach up to 70%. The global economic impact of PPN is estimated to exceed $150 billion annually.

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How nematodes infect crops

Plant-parasitic nematodes use a needle-like structure known as a stylet to penetrate plant tissue and extract nutrients. They are classified according to their feeding habits:

• Endoparasites: Completely enter the plant and feed internally.
• Semi-endoparasites: Insert only their heads into the plant while the rest of their bodies remain outside.
• Ectoparasites: Remain outside the roots and feed by inserting their stylets.

How to identify nematode damage

Since PPN primarily attack the root system, they disrupt water and nutrient absorption, leading to weak, stunted plants with yellowing leaves. These symptoms are often mistaken for nutrient deficiencies. However, a closer inspection of the roots may reveal lesions, cysts, or galls, helping to identify the specific type of nematode infestation.

How nematodes spread and how to prevent infestations

PPN can spread easily from one field to another through soil, plant material, and farm machinery. To prevent this, farmers are advised not to transport soil or plant residues between fields. Additionally, farm equipment should be thoroughly washed with water after being used on infested land.

Management and control strategies

To keep nematode populations below economic threshold levels, farmers must implement various control measures, including:

• Using nematode-resistant crop varieties.
• Crop rotation, cover cropping, and intercropping to enhance soil health.
• Organic soil amendments that promote microbial diversity and improve resistance to PPN.
• Limited use of chemical nematicides, as they can negatively impact soil health in the long term and increase nematode outbreaks in subsequent seasons.

Common nematodes affecting South African agriculture

South African farmers should be particularly aware of root-knot nematodes (RKN), cyst nematodes, and root-lesion nematodes (RLN), as these species cause significant economic losses.

New diagnostic resources for farmers

UFS is in the process of establishing a state-of-the-art nematology laboratory, which will also feature a diagnostic facility for farmers. Farmers will be able to send soil and root samples for analysis. Using advanced technology, experts will identify and quantify nematode species and provide detailed reports with tailored management recommendations.

Controlling PPN is crucial for sustainable agricultural production. By leveraging innovative technology and integrated management practices, farmers can mitigate the impact of nematodes and protect their crops.

OFM Agri cg