Parasitism of the Citrus Nematode, Tylenchulus semipenetrans, by Pasteuria penetrans in Iraq.

Pasteuria penetrans Sayre & Starr parasitizes several nematode species and is considered a promising biocontrol agent of the root-knot nematode, Meloidogyne spp. (1,7). Numerous plant-parasitic nematodes, including Tylenchulus semipenetrans, however, are seldom if ever infected by this biocontrol agent (3). Tylenchulus semipenetrans Cobb is the most economically important and widespread nematode pest of citrus worldwide. In Iraq, it occurs in more than 90% of the citrus orchards and nurseries (4). Specimens of T. semipenetrans infected by P. penetrans were detected during routine collection of soil and root samples from T. semipenetrans-infected citrus trees at A1Dorah, Baghdad. T. semipenetrans motile stages were extracted from soil and roots by a modification of Cobb's sieving and decanting method (6) and from sedentary adult females by maceration or dislodging. Nematode stages infected with P. penetrans were examined in a water suspension through a compound microscope. Only second-stage juveniles (J2) and adult males had P. penetrans spores affixed to their cuticles (Fig. 1 A-C). Juveniles with attached spores tended to aggregate in groups of 2-5 nematodes and stick to each other. Similar observations of Meloidogyne javanica were made (3).