Application of Nematophagous Fungi and Salicylic Acid as Biological Control Agents against Root-Knot Nematode, Meloidogyne incognita Infected Gladiolus: A Valuable Export Plant

Abstract

This study aims to use safety agents to control the root-knot nematode, Meloidogyne incognita infected gladiolus plants (Gladiolus grandiflorus) in pots under field conditions, directly by using two nematophagous fungi, Purpureocillium lilacinum which parasite on nematode eggs and Hirsutella rhossiliensis which parasite on second stage juvenile of nematode , and indirectly by using treatment of salicylic acid (SA). The applied agents applied either individually or in combination, reduced nematode numbers and improved gladiolus vegetative and flowering characteristics. Tri-treatment (SA + P. lilacinum + H. rhossiliensis) achieved the best results aptly, leading to increase reduction percentage of nematode juveniles to 80.2%, decreased egg masses production and root gall index to 91.3 and 83.3%, respectively, compared with bionematicide Tervigo (Abamectin) which gave reduction percentage of nematode juveniles as 78.9%, decreased egg masses production and root gall index (80.0, 66.7%, respectively). Also, the previous tri-treatment improved flowering traits as it led to an increment proportion of flowering stem length (58.6%); number of florets/spike (46.2%) and fresh weight of inflorescence (67.9%) compared with Tervigo (43.3, 41.8 and 54.2%, respectively). In addition, tri-treatment (SA + P. lilacinum + H. rhossiliensis) significantly improved chemical properties of N, P, K and total carbohydrate (76.8, 52.4, 47.4 and 31.4%, respectively) compared with Tervigo (42.7, 23.8, 6.3 and 4.5%, respectively). The obtained results can be concluded that, both nematophagous fungi complement each other, and adding SA led to their superiority in its effectiveness for M. incognita control over the nematicide Tervigo (Abamectin). Therefore, the use of chemical nematicide in which causes harmful effects to environment and humans should be reduced or substituted with clean biological control.