Control of Meloidogyne chitwoodi (Columbia root-knot nematode) by microbial soil inoculants in potatoes (Solanum tuberosum)

Abstract

Columbia root-knot nematode (Meloidogyne chitwoodi Golden et al) is a major pest in commercial potato production in the northwestern, United States of America. M. chitwoodi infestation is widespread throughout the potato (Solanum tuberosum) growing regions of the U.S and other areas of the world. Meloidogyne spp. causes severe crop damage and economic losses in a broad range of economically important crops. Traditionally, M. chitwoodi has been controlled by the applications of chemical-based soil fumigants and nematicides. Chemical based controls have shown good effect at controlling M. chitwoodi, but due to their human toxicity, possible damage to the environment, development of nematode resistance to chemical nematicides, decreased availability of labeled chemical nematicides and the high cost of chemical nematicides there is a need for alternative methods to control M. chitwoodi. Specific soil microorganisms have been found to be antagonistic and parasitic to M. chitwoodi and other Meloidogyne spp. in potatoes and several other crops. It has also been proposed that the use of soil microorganisms that are antagonistic and parasitic to plant parasitic nematodes are an essential component to long term sustainable Integrated Nematode Management (INM). Due to the agricultural need for the development of alternative control methods of Meloidogyne spp. in crop production worldwide two commercially available microbial soil inoculant products were tested under greenhouse and open-field conditions. The two commercially available microbial soil inoculant products that were tested are NemaRoot, which contains Purpureocillium lilacinus (formally known as Paecilomyces lilacinus) and BioFit N, which contains Azotobacter chroccum, Bacillus subtilis, Bacillus megaterium, Bacillus mycoides, and Trichoderma harzianum. Previous findings have shown that Bacillus subtilis, Bacillus megaterium, Trichoderma harzianum and Purpureocillium lilacinus all have the ability to control Meloidogyne spp. to varying degrees in a number of diverse crops. The greenhouse experiments that were conducted for this research showed that NemaRoot was able to reduce M. chitwoodi root galling by 64% (P < 0.001), eggs by 74% (P < 0.001) to 91% (P < 0.001), second-stage juveniles in the substrate by 80% (P < 0.001), the reproductive factor by 67% (P < 0.001) to 80% (P < 0.001) and potato tuber damage by 77% (P < 0.001) to 82% (P < 0.001) in potatoes. The greenhouse experiments also showed that BioFit N was able to reduce M. chitwoodi root galling by 73% (P < 0.001, eggs by 81% (P < 0.001) to 97% (P < 0.001), second-stage juveniles in the substrate by 81% (P < 0.001), the reproductive factor by 82% (P < 0.001) to 87% (P < 0.001) and potato tuber damage by 78% (P < 0.001) to 78% (P < 0.001) in potatoes. The commercial open-field potato experiment showed that 2, 3 and 4 applications of BioFit N at a rate of 1.12 kg/ha per application were able to control M. chitwoodi tuber damage as well as 2 applications of Vydate (Oxamyl) at a rate of 2.2 L/ha per application. These results show that biocontrol of M. chitwoodi with microbial soil inoculants are an effective control method; especially, when used as a part of an Integrated Nematode Management (INM) strategy.