Tylenchulus semipenetrans

[1] The citrus nematode was first discovered in California in 1913 by J. R. Hodges, a horticultural inspector for Los Angeles County, and was later described and named by Nathan Cobb that year.

The pore is surrounded by small, irregularly shaped lobes; and the excretory duct is directed forward.

The citrus male nematodes are required for reproduction with females when their posterior end is exposed on the root surface.

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.

The nematode feeding from these nurse cells reduces the amount of water and nutrients available to the growing plant.

The infected root systems due to the nematode damage lose the ability to absorb enough water and nutrients for normal growth.

[5] According to E. Cohn, 4000 juveniles per gram of root are the damage threshold for slow decline disease in Israel.

[6] In Cyprus, the growers need to apply nematicides when the nematode densities reach 5000 juveniles per 250 cm3 (15 cu in) in soil.

For low presence of nematodes, a pesticide application may not be economical, but at medium to high populations, nematicides can be prevent significant decline in fruit size and yield.