Citrus burrowing nematode

Systematic position and pathogen type. Radopholus citri belongs to the phylum Nematoda, class Chromadorea, order Tylenchida, and family Pratylenchidae. It is a microscopic, migratory endoparasitic nematode that specifically targets the root systems of citrus trees. As a phytopathogen, it causes localized destruction of root tissues, leading to severe physiological dysfunction in host plants.

Diseases and affected crops. This nematode primarily infests trees within the genus Citrus. The damage is characterized by the formation of lesions on roots, leading to a condition often described as "slow decline." Symptoms include stunted growth, leaf chlorosis, thinning of the canopy, and reduced fruit yields. By damaging the root cortex, the nematode impairs the tree's ability to absorb water and essential nutrients.

Biology and life cycle. The life cycle of Radopholus citri includes both soil-dwelling stages and stages within the plant tissue. Females lay eggs inside the root cortex. Upon hatching, the larvae and adults feed on the parenchyma cells, creating tunnels as they migrate. The entire cycle can be completed in approximately three to four weeks, depending on favorable temperature conditions, allowing for rapid population buildup.

Developmental conditions and impact. The spread of this pathogen is largely attributed to the movement of infested nursery stock, contaminated soil, and surface water runoff. Sandy soils that provide easy movement for the nematodes are particularly susceptible. The impact is profound, especially in nursery settings where young plants may be killed, and in established orchards where the cumulative effect of root destruction leads to long-term economic losses.

Protection and control measures. Management of Radopholus citri is primarily preventative, as curative options for established infections are limited. Key control strategies include:

• Strict adherence to quarantine regulations and nursery certification programs.
• Heat treatment of planting materials to ensure they are nematode-free.
• Implementing soil fumigation in nursery sites prior to planting.
• Use of resistant citrus rootstocks that prevent nematode penetration.
• Managing irrigation to avoid the spread of infested water to healthy areas.