Since chemical pesticides have numerous negative effects on the environment, the study aimed to evaluate thebionematicidal effect of aqueous leaf extracts of chinaberry, datura, marigold and oleander at concentrations 0.1 g/ml (10% w/v) on root-knot nematode, Meloidogyne incognita egg hatching and juvenile mortality in vitro besides in vivo efficiency of different rates and times of soil drenching application insuppress nematode infection progress on pepper plants.
Phytochemical analysis of aqueous plant extracts revealed that the highest contents of flavonoids, phenolics, saponins and tannins presented in chinaberry and marigold followed by oleander responsible for their highest effect as bionematicide, whereas the least content was found in datura extract.
In vitro, the standard aqueous extract of marigold gained the highest ovicidal effect followed by datura then chinaberry and oleander and with percent, egg masses hatching inhibition 91.43, 59.78, 56.88, and 55.48% after 5 days of exposure, respectively. Marigold extract showed high hatching inhibition on treated egg masses even with half concentration (5 % w/v), with an increase in efficiency of other plant extracts against hatchability of free eggs.
The descending order of plant extracts efficacy against J2 treated with 10 % (w/v) was marigold followed by oleander, datura and chinaberry recorded 75.60, 65.60, 54.20, and 52.20 % mortality, respectively after 5 days post-treatment and the larvicidal effect was directly proportioned to concentration and exposure time.
In vivo, plant extracts significantly increased biomass of infected pepper plants and decreased reproduction of M. incognita as measured by IJs/100 g, egg masses numbers beside the number of galls and size as compared to the infected plants. Among this, oxamyl treatment surpassed composted chicken manure followed by marigold extract treatment. Twice application achieved significant amending plant growth and decreased nematode reproduction particularly in marigold extract treatment.