Sudan lesion nematode

The Sudan lesion nematode, Pratylenchus sudanensis, belongs to the order Tylenchida and the family Pratylenchidae. It is a microscopic endoparasite that inhabits both soil and plant root tissues.

Adult individuals possess a worm-like body approximately 0.5–0.7 mm in length. They are equipped with a strong mouthpart, known as a stylet, which enables them to mechanically damage plant cells during feeding.

Identification of this species under field conditions is impossible without laboratory analysis. To confirm the presence of the nematode, specialists extract them from soil samples or root tissues followed by microscopic examination.

Biologically, this species is a migratory endoparasite. Unlike gall-forming nematodes, they continuously move within the root cortex without inducing the formation of visible galls.

The species prefers warm climates and well-aerated soils, where their rate of reproduction and migration is significantly higher compared to heavy clay soils.

This pest affects a wide range of agricultural crops. Cereals, legumes, certain vegetable crops, and woody plants are particularly susceptible to infestation.

The primary host crops in agroecosystems include maize, sorghum, and various grain legumes, which provide optimal conditions for the nematode to feed and multiply.

Damage to the root system results in stunted growth of the plant's aerial parts. As vascular bundles are destroyed, the transport of water and essential mineral nutrients is severely compromised.

The damage caused by Pratylenchus sudanensis is often underestimated, as infestation symptoms are frequently mistaken for nutrient deficiencies or drought stress.

Massive reproduction of these nematodes leads to a sharp decline in marketable yield of root crops and grain quality, resulting in significant economic losses for farmers.

The life cycle of the pest is closely linked to soil temperature. Activity begins when soil temperatures rise above 10–12 degrees Celsius.

The most favorable period for population growth occurs during the active growth phase of the plants. Several generations of the parasite can develop within a single growing season.

Nematodes are capable of surviving in the soil for long periods as eggs or larvae, enduring unfavorable conditions through a state of dormancy.

During the autumn, the pest typically migrates to deeper soil horizons where temperatures are more stable, allowing it to survive the winter season effectively.

Peak population densities are generally recorded in the middle of the growing season when plant root systems are fully developed and readily available for feeding.

During the early stages of infestation, plants appear chlorotic, showing stunted growth and general development delays compared to healthy plants in control areas.

The root systems of infested plants often exhibit characteristic brown lesions or necrotic spots, which is the reason for the common name of the pest.

In cases of severe infestation, roots become brittle and growth ceases, leading to the development of a stunted or "bearded" root appearance due to secondary root formation.

In the field, infestations often appear in patches; affected plants are distributed unevenly, creating a mosaic-like pattern of growth across the field.

• leaf yellowing and wilting;
• reduced turgor pressure during peak sunlight;
• necrosis of fine rootlets;
• delays in flowering and maturity phases.

Crop rotation is the primary method of control. Utilizing non-host crops in rotation cycles significantly reduces the population of Pratylenchus sudanensis in the soil.

Implementing fallow periods or using green manure crops with nematocidal properties (such as mustard or oilseed radish) helps to naturally rehabilitate the soil health.

Agricultural practices focused on improving soil structure and maintaining proper moisture levels limit the mobility of larvae and their ability to infect new plant hosts.

Chemical control may involve the application of specialized nematocides (fumigants) during soil preparation, although this approach is costly and carries environmental considerations.

The use of certified, disease-free seed material is essential to prevent the introduction of the pest into clean fields via soil contaminated with seeds.