Efficacy of four plant extracts on nematodes associated with papaya in Sindh, Pakistan

Abstract

This investigation attempts to evaluate the effect of ethanolic extracts of four plant species, Azadirachta indica (neem), Withania somnifera (ashwagandha), Tagetes erecta (marigold) and Eucalyptus citriodora (eucalyptus), against nematodes associated with papaya (Carica papaya) and to assess their influence on papaya growth and yield. While fresh shoot weight of papaya seedlings in pots was significantly increased by the plant extracts, in general, the fresh root weight remained unaltered compared to the controls. The number of Meloidogyne incognita juveniles, root-knot index and the number of egg masses per root were remarkably reduced by all treatments. The population densities of Meloidogyne incognita, Helicotylenchus multicinctus and Hoplolaimus indicus, the main nematode species associated with papaya, were significantly reduced in the field by all four plant extracts. Meloidogyne incognita and H. multicinctus were most affected by Withania, H. indicus by Tagetes. The papaya yield was increased by the treatments in the following order: Withania somnifera > carbofuran > Azadirachta indica > Tagetes erecta > Eucalyptus citriodora. The possible mechanisms of nematicidal effects of the plant extracts are discussed.