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Tylenchulus semipenetrans Cobb
Tylenchus semipenetrans

Nematoda, Tylenchida, Tylenchidae .

Citrus root nematode

Description, Biology, Life Cycle, Damage, Common Names, Images

- The adult female is extremely small and is generally to be found at the surface of a radicle as a small bag terminated by a peak if it has only recently become attached. The older female is hidden in the egg mass which it has laid and which measures about 0.5 mm across.

- Host plants include mainly Citrus, vine and olive.
- Eggs hatch a few days after egg-laying and it is possible to distinguish between male and female juveniles from the 2nd stage.
- Male juveniles become sexually mature in 1 week and live as ectophytes. Without growing, they emerge as males devoid of stylet and do not feed but can survive in the soil for several months.
- Female juveniles live as ectophytes and then half-penetrate the root (*) . The cells surrounding the head of the nematode change into a nutritious area. The posterior part of the female remains outside the root, enlarges and blisters.
Egg-laying (about 100 eggs are laid) takes place in a jelly-like covering which makes soil particles stick together.

[R]Life Cycle
- The length of the life-cycle reaches 6-8 weeks and fertilization does not seem to be obligatory. This nematode species occurs in very large numbers and can survive up to 30 months without a host.

- Affected trees firstly exhibit a lack of vigour which is followed by chlorosis. Leaves fall, which may result in the drying out of the tips of twigs (*) .
This affliction has been given the name of 'slow decline' owing to the slow development of the symptoms. The most seriously affected trees no longer yield.

[R]Common Names
DE: Orangen-Wurzelnematode ES: Nematodo de la raiz de los agrios FR: Nématode des racines des agrumes IT: Nematode degli agrumi PT: Nemátodo das raízes das laranjeiras GB: Citrus root nematode

[R] Images

  1. Tylenchulus semipenetrans Cobb (INRA / Antibes)
    Young female inserted in root of citrus
  2. Tylenchulus semipenetrans Cobb (BASF)
    Damage on citrus Attacks cause the tree to decline.
  3. Tylenchulus semipenetrans Cobb Adult females fixed to roots Individuals colored by acid fuchsin.

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