THE OCCURRENCE OF BURROWING NEMATODES ON BANANA IN LEBANON AND THEIR CONTROL USING PLANT EXTRACTS AND ESSENTIAL OIL OF Origanum Sp.
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- In a survey 93 samples were collected from banana plantation in different regions on the coastal area of Lebanon. Almost all the collected soil samples (96.7%) and 88.2% of the collected root samples were infected with nematodes. The soil infestation ranged between 0 to 39 nematodes /g soil, while the number of nematodes in root samples ranged between 0 to 72.5 nematodes /g roots. Radopholus similis were identified in both, soil and root, samples as well as Rotylenchulus sp., Xiphinema sp., Longidorus sp., Meloidogyne spp., Helicotylenchus sp., and Pratylenchus spp. Crude oil and eight pure components of Origanum were tested against Radopholus sp. Thymoquinone (LC 50 =0.045 µl/ml), thymol (LC 50 =0.18 µl/ml), and carvacrol (LC 50 =0.9 µl/ml) were found to be the most toxic against Radopholus similis after 4 hrs. of exposure, followed by those of p-cymol (LC 50 =6.3 µl/ml), and (1S)-(-)-α-Pinene (LC 50 =36 µl/ml). However, caryophyllene (LC 50 =49 µl/ml), terpinene (LC 50 =58 µl/ml), and (1R)-(+)-α-Pinene (LC 50 =58 µl/ml) were less effective against Radopholus even after 24 hrs. of exposure. Crude oil (LC 50 =4.8 µl/ml) also gave high degree of nematicidal activity on Radopholus similis 4 hrs. post treatment. The results of pot experiments revealed that the most significant effect on the number of nematodes was with Cucurbit sp. (89%) followed by Chrysanthemum coronarium (88%), Melia azadirachta (85%), Origanum syriacum (77%), Foeniculum vulgare (68%), Inula viscosa (66%) and Allium sativum (44%) extracts. The highest concentration of essential oils (5-6%) was detected in leaf extracts of Origanum.