Abstract :
The citrus nematode Tylenchulus semipentrans is an important nematode that distribute in citrus orchards and cause slow decline to the plant, so this study was conducted to evaluated the antagonistic effect of some biocontrol agents Trichoderma harzianum and Bacillus subtilis against citrus nematode Tylenchulus semipentrans and the results shown that both biocontrol agents affect the J2 population of Tylenchulus semipentrans and the bioagent T. harzianum was more effective than B. subtilis in supressing the j2 population in vitro. The mean of mortality in the case of T. harzianum was 67.00 % as compared with the B. subtilis which was 43.56% at the stock (S), and the effect increased with increasing of exposure time and the mean of mortalities were 45.10, 73.20, and 82.70% after 24, 48 and 72h in the case of T. harzianum and 21.30, 38.00, and 71.33% after 24, 48 and 72h in the case of B. subtilis at the same concentration (S). In the field expriement it was observed through the results that the bioagents (Trichoderma harzianum and Bacillus subtilis) hav great efficacy against nematodes in the field where the percentage of reduction reach to 70.67% in the case T.harzianum while in the case of B. subtilis was 59.10% as compared with the control which give the rate 18.80%.
