🪱 Citrus Nematodes

Species, Biology, Symptoms, Integrated Management

Which of the following is not correct regarding citrus nematodes?
  • Citrus nematode (Tylenchulus semipenetrans)
  • The generic name Tylenchulus derived from Latin: Tylos means Knob and enchos means spear.
  • And specific name semipenetrans denotes nematode’s semi-endoparasitic nature.
  • The common name ‘citrus nematode’ signifies specificity to its host i.e. citrus.
  • Also known as stunt or stylet nematode.
  • Cobb in 1912 observed this nematode associated with diseased citrus trees in California (USA)
  • In India, it was first reported by Siddiqi in 1961 from Aligarh (UP).

Biology

  • Second stage Juveniles (J2) infects the fine feeder roots.
  • The young females penetrate deeper in the cortical tissue where they establish a permanent feeding site and become sedentary. At feeding site 6-10 cortical parenchyma cells, known as nurse cells.
  • Therefore, this nematode is cortical sedentary semi-endoparastic feeder.

Symptoms

  • It causes Slow decline of citrus or commonly known as Citrus decline.
  • It includes yellowing of leaves, defoliation, premature shedding of fruits, reduction in number and size of fruits, increasing number of dead twigs from top, and weak seasonal flushes.
  • It is known as citrus decline because it primarily affects citrus trees, leading to a decline in their overall health and productivity.
  • The feeder roots show the typical symptoms. The infested roots appear dark, while healthy roots are creamish.

Management

  • Incorporation of Neem Cake @ 1kg/tree along with carbofuran @ 2 kg a.i./ha.
  • Generall management practices.
References 
- Dropkin, V.H. 1980. Introduction to plant nematology. John Wiley and sons, INC. New York.
- Singh, R.S and Sitaramaiah, K. 1994. Plant pathogens. The plant parasitic nematodes. Oxford & IBH Pub. Co. Pvt. Ltd. New Delhi.
- Parvata Reddy, P. 1983. Plant nematology. Agricole Pub. Co., New Delhi.
- Southey, J. F. Laboratory methods for work with plant and soil nematodes Tech.
- Bull. Min. Agric. Fish. Food. Her Majesty’s Stationary Office, London.
- Walia, R. K and Bajaj, H. K (2014). Textbook of Introductory Plant Nematology. Directorate of Knowledge Management in Agriculture, ICAR, New Delhi. 
- Kumar, V., Khan, M.R. & Walia, R.K. Crop Loss Estimations due to Plant-Parasitic Nematodes in Major Crops in India. Natl. Acad. Sci. Lett. 43, 409–412 (2020). https://doi.org/10.1007/s40009-020-00895-2
- Figure 1: Source: A: Maggenti, 1981, B-E: Franklin, 1973

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