NEMATICIDAL PROPRIETIES OF COMMERCIAL SEED OILS OF CERTAIN MEDICINAL PLANTS ON EGG HATCHING AND JUVENILE MORTALITY OF THE ROOT-KNOT NEMATODE, Meloidogyne incognita In Vitro

Abstract

Cold pressed commercial seed oils of castor bean (Ricinus communis) colocynth, (Citrullus colocynthis) jojoba, (Simmondsia chinensis) and moringa (Moringa oleifera) at three concentrations (S, S/2 and S/4) showed nematicidal activity against egg-masses, free eggs and second stage juveniles of Meloidogyne incognita in vitro experiments. Egg hatching and juvenile mortality were significantly (P ≤0.05) influenced by tested oil, concentration and exposure time. Colocynth and jojoba oils gave a relatively higher effect followed by moringa oil while castor bean oil was the lowest effective one. Percentages inhibition in hatching when 5 fresh and uniform size egg-masses or 100 free eggs were separately exposed to the standard solution of colocynth, jojoba, moringa and castor bean after 7 days post treatment were 89.7 (63.8), 88.8 (54.4), 79.8 (52.5) and 43.4 (41.2)%, respectively. Egg hatching inhibition was inversely proportion to the dilution of the tested oil. On the other hand, as exposure time increased from 1 to 7 days after treatments, ovicidal effect of the tested oils was obviously increased at all the tested concentrations in treatments of egg-masses while the opposite was true in treatments of free eggs. Statistical analysis (P ≤ 0.05) showed that egg-masses were more sensitive to the tested oils compared to free eggs with all the tested oils at the three concentrations. Similarly, the tested oils were found to be significantly (P ≤ 0.05) effective against second stage juveniles of M. incognita. Among which, jojoba was the most effective oil followed by colocynth and moringa while castor bean was the lowest toxic one. The highest value of juvenile mortality was detected with jojoba at the standard solution, 7 days after exposure (48.6 %) followed by colocynth (43.0%) and moringa (31.0%) while castor bean (17.4%) was the lowest toxic one. Juvenile mortality was dependent on the concentration and exposure time also. Generally, in vitro treatments revealed that the tested oils displayed nematicidal effect against egg-masses, free eggs and juveniles of M. incognita. Further studies are needed under greenhouse and field conditions.