Effects of plant shoots extracts on egg hatching and mortality of second-stage juvenile of the root-knot nematode Meloidogyne incognita under laboratory conditions

Root-knot nematodes (Meloidogyne spp.) are the most damaging group of plant-parasitic nematodes, causing substantial reductions in yields of agriculture worldwide. Meloidogyne incognita and M. javanica are the most widespread species globally and in Iran, respectively. This study was conducted to evaluate the effect of different plant shoot extracts on the mortality of second-stage juveniles (J2) or egg hatching of the nematodes under laboratory conditions. First, the effect of 50% aqueous extracts from 44 plant species on J2 mortality of M. javanica was evaluated. Of the 18 plants that showed a mortality effect of over 50%, the plants catmint (69.3%), hedge mustard (66.7%) and sun spurge (63.3%) were the most effective plants. Next, aqueous, ethanolic, hexanoic and aqueous-ethanolic-hexanoic extracts from seven of the 18 effective plants were tested individually or in combinations in distilled water and sterile sand on M. incognita egg hatching and J2 mortality. In sterile sand, aqueous and aqueous-ethanolic-hexanoic extracts of rapeseed, sun spurge, chalk plant and arugula reduced egg hatch by 59.3-69.9 and 61.0-72.0% after eight days, respectively. The aqueous and aqueous-ethanolic-hexanoic extracts of these plants also caused a mortality of 47.5-56.0% and 44.5-54.5% of J2 after five days, respectively. In distilled water, aqueous or aqueous-ethanolic extracts of these plants and hedge mustard caused 46-66% and 60-69% J2 mortality after 48 hours, respectively. In all tests, rapeseed, sun spurge, chalk plant, hedge mustard and arugula showed the highest efficacy. The efficacy of aqueous, aqueous-ethanolic or aqueous-ethanolic-hexane extracts was higher than organic solvent extracts alone. However, combining plants did not increase the efficacy of their extracts. These results suggest that plant extracts have a high potential to reduce egg hatching and mortality of second-stage juvenile of root-knot nematodes, and that an alternative approach to reduce the use of the chemical nematicides can be provided by identifying and extracting their effective components and producing plant-based nematicides.