page_title: Tylenchulus semipenetrans
section_title: Life cycle and reproduction
hierarchical_section_title: Tylenchulus semipenetrans / Life cycle and reproduction
caption_attribution_description: English: Life stages of citrus nematode
context_page_description: Tylenchulus semipenetrans is a species of plant pathogenic nematodes and the causal agent of slow decline of citrus. T. semipenetrans is found in most citrus production areas and diverse soil textures worldwide. Their feeding strategy is semi-endoparasitic and has a very narrow host range among commonly grown crops. These nematodes are considered as major plant-parasitic nematode because they can cause 10-30% losses reported on citrus trees. They also parasitize other hosts such as olive, grape, persimmon and lilac. The citrus nematode was first discovered in California in 1913 by J.R. Hodges and was later described and named by Nathan Cobb that year.
context_section_description: The life cycle of the female citrus nematode is 6–8 weeks long, whereas the male citrus nematode only lives for about 7–10 days. These nematodes reproduce by amphimixis and parthenogenesis. The first-stage juvenile (J1) undergo one molt while still in the egg. The J1 has no stylet. The second-stage juveniles (J2) hatch from the eggs and the sex can be distinguished at this stage. The J2 male is short and fat. Juveniles will undergo two more molts into the J3 and J4 before becoming young adults. The citrus male nematodes are required for reproduction with females when their posterior end is exposed on the root surface. The J2 male has a stylet while the J3 and J4 have a weaker stylet. The J2 female is longer and thinner than males and they do not molt until feeding site is established. The female juveniles begin feeding ectoparasitically on epidermal root cells. It is not until the female citrus nematode becomes a young adult that she becomes the infective stage.  The anterior end of the young female penetrates into the cortex of the root and begins feeding on 3-6 nurse cells. This intense feeding by the adult female will cause the posterior end to enlarge outside the root and start producing eggs. After fertilization, the female lays its eggs outside of the root in a gelatinous matrix extruded from excretory pore located near the vulva.
caption: Life stages of the Citrus nematode,Tylenchulus semipenetrans. Source: Nemaplex UC IPM)
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