Plant Parasitic



Webmaster: Daniel Snyder

Last Edited: May 30, 2002


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

The UC Davis page on the genus Tylenchulus.