Control of citrus nematode Tylenchulus semipenetrans (Tylenchida: Tylenchulidae) using plant-based products under in vitro and in vivo conditions

The citrus nematode (Tylenchulus semipentrans) is one of the most important parasitic nematodes affecting citrus trees, causing gradual decline and reduced yield. Potential risks, high costs and environmental consequences of chemical compounds have led researchers to explore non-chemical methods such as using plant-based products for nematode management. The present study was conducted to control citrus nematodes using essential oil and water extract of Artemisia annua and methanolic extract of Melia azederach under laboratory and greenhouse conditions. In vitro bioassays were carried out, and the effects on toxicity, mortality, and egg hatching were assessed. The highest in vitro nematistatic activity was recorded for 250 ppm of A. annua essential oil and 500 ppm of M. azederach methanol extract by 100% paralysis of nematodes after 48 h. Furthermore, the highest nematicidal activity of A. annua essential oil, aqueous extract and methanolic extract of M. azederach was recorded to be about 60−100%, 40−87% and 38−100%, respectively. Among all concentrations of M. azederach methanolic extract and high concentrations of A. annua essential oil and aqueous extract, the repellents and motility inhibitors for nematodes were found. The results of egg hatching showed that essential oil of A. annua at a concentration of 250 ppm had the greatest reduction of egg hatching. In a greenhouse experiment, all the treatments were found to be significantly effective against the citrus nematode population in soil and roots compared to the control. Maximum reduction was observed in 500 ppm of methanolic extract of Melia azederach. Growth parameters (plant height, fresh and dry shoot and root weight) increased compared to the control when treatments were applied. Based on the results, plants such as A. annua and M. azedarach are considered to be promising control agents for citrus nematodes. The results indicate that products derived from these plants may be potential candidates for formulating new nematicides suitable for sustainable nematode management, although field trials are still needed to demonstrate their effectiveness for commercial use.