Citrus slow decline Tylenchulus semipenetrans

Citrus slow decline Tylenchulus semipenetrans

• 1.
  Citrus Slow Decline Muhammadammar UCA, UOS
• 2.
  Importance • found inevery citrus growing region of the world • 30-60% losses • 1st reported in Pakistan in an orange orchard at Lyallpur in1962 • Cosmopolitan • cause injury to 50 species or hybrids of Citrus in the family Rutaceae
• 3.
  Etiology • C:O Tylenchulussemipenetrans (Citrus nematode, citrus root nematode) California in 1913 by J.R. Hodges and was later described and named by Nathan Cobb Evolved in Far East
• 4.
  Host range Grape Persimmon LilacOlive
• 5.
  Disease cycle • Liveon alternate hosts (olive grapevines) • Females lay eggs in gelatinous substance, remain safer for longer time • In soil may occur as deep as 4 meters • In new location spread through planting materials • Only 2nd stage is infective • amphiximis and parthenogenesis
• 6.
  • Life cycleduration 4-6 weeks • J2 penetrate outer layer of cortex. • Nematode molts 3 times to become adult. • Posterior remains outside and female swells with eggs
• 7.
  • Female feedsand destroys cells, leaving space for head to move around • Sedentary semi-endoparasite • 40-60 eggs per female • Development of J2 stops if host is not present. J2 can persist in soil for years until host is present.
• 8.
  Symptoms • Suppression ofcitrus tree growth, lack of vigor or decline symptoms, yellowing of foliage and small size of fruit • The females penetrate into the cortex cells, become sedentary and form multiple‘nurse’ cells. The nematode feeding from these nurse cells reduces the amount of water and nutrients available to the growing plant.
• 10.
  • Infected rootsare thicker, darker, decayed and appear dirty. Soil particles stick the gelatinous matrices excreted by the females. • Yellowing of foliage, leaf curling and dieback are consequences of insufficient root development and decayed young roots
• 11.
  • Management: • Dippingthe roots in 45°C water for 25 min, this kills the nematodes but does not harm the plant • For cultural practices, the container-grown citrus can be treated with steam and soil solarization
• 12.
  • Nematicide (Chloropicinand Aldicarb) to reduced initial population densities. • Resistant rootstocks to suppress nematode population density. • Hybrid rootstock (Swingle citrumelo) is highly resistant to the citrus nematode.
• 13.
  • Duncan' grapefruitand a trifoliate orange (Poncirus trifoliata (L.) Raf.), developed by Walter Tennyson Swingle