Pathogenicity of Meloidogyne incognita Race 1 on Turmeric (Curcuma longa L.) as Influenced by Inoculum Density and Poultry Manure Amendment

A glasshouse experiment was conducted to assess the pathogenicity of Meloidogyne incognita race 1 on turmeric (Curcuma longa L.) at three inoculum densities (0, 2500, 5000 eggs plant super(-1)) and soil amendment with different levels of Poultry Manure (PM) (0, 10, 20, 30 and 40 t ha super(-1)). The results obtained showed that root-galling and egg production decreased in a linear response to increasing PM level at both low and high inoculum densities (r = -0.88 and r = -0.85, respectively; p less than or equal to 0.01). The lowest gall index and egg mass index of 2.0 were recorded in plants amended with 40 and 30 t ha super(-1) PM, respectively. The high nematode density was more pathogenic (p less than or equal to 0.05) than the low density. Shoot length, fresh shoot and root weights responded in a curvilinear pattern with increasing levels of PM. In general, these growth variables increased with increase in PM level up to 20 t ha super(-1) and then declined with further increase. At high inoculum density, shoot growth was enhanced by 242 and 58% with 20 and 40 t ha super(-1) PM relative to unamended soil, respectively. Conversely, fresh root weight was increased by 120% and reduced by 12.8% with 20 and 40 t ha super(-1) PM, respectively. From this study, it could be inferred that higher levels of PM were highly nematicidal but phytotoxic to turmeric plants; the optimal rate of PM amendment is predicted to be 18-22 t ha super(-1). However, for this method to be incorporated into Integrated Nematode Management Programme of turmeric, field trials are needed for the optimization of the quantity, time and method of application.