Genus Tylenchulus

The Citrus Nematode

Most important species: T. semipenetrans

• only one species of economic importance in agriculture
  
• limited host range (rutaceous plants, olive, grape, persimmon)
  
• spread by infested nursery stock (which have no obvious symptoms)
  
• causes "slow-decline" of citrus
  
• semi-endoparasite (forms nurse cells in root)
  
• young female is infective stage
  
• long life cycle(6-8 weeks)
• J2 sexual dimorphism
• develops to adult in 7 days without feeding
• 26% are non-infective males with esophoguses and stylets that degenerate
• 70-100 eggs laid in a gelatinous matrix
• 4000 nematodes /g root required to cause severe damage
• general symptoms are similar to nutrient deficiencies
• symptoms not apparent until 5-10 years after population peak
• feeds on 6-16 cortical(nurse) cells that show no hypertrophy or hyperplasia
• syncytium has some wall ingrowths and the cytoplasm becomes granular with enlarged nuclei