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Tylenchulus semipenetrans Cobb
Tylenchus semipenetrans

Nematoda, Tylenchida, Tylenchidae .

Citrus root nematode

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

[R]Description
- 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.

[R]Biology
- 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.

[R]Damage
- 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.
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  3. Tylenchulus semipenetrans Cobb Adult females fixed to roots Individuals colored by acid fuchsin.

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