Disease management and yield loss model of Fusarium wilt of cotton (Gossypium hirsutum L.) caused by Fusarium oxysporum f.sp. vasinfectum Snyder and Hansen

The population of Fov [Fusarium oxysporum f.sp. vasinfectum] was lowest in the potted soil planted to corn and highest in plots grown with weeds. Cotton and mungbean favored the increased or survival of Fov in the soil. The number of Fov was lower in the soil planted to CRDI-1 compared with UPL-C2. The population of Fov in naturally infested soil was suppressed when corn was used as previous crop. Plots previously grown to peanut, mungbean and weeds such as Cenchrus echinatus, Eleusine indica, Euphorbia heterophylla, Ipomoea triloba, Amaranthus spinosus and Cyperus rotundus favored the survival of the pathogen. The number of Fov was significantly reduced in the soil planted consecutively with corn. A. spinosus and C. rotundus favored the survival of the pathogen. The number of Fov was significantly reduced in the soil planted consecutively with corn. The result suggests that cotton variety does not exert a direct effect on the population of Fov and Trichoderma spp in the soil. There was no discernible relationship between the population of Fov and Trichoderma spp CRDI-1 outyielded UPL-C2 when they are planted in Fusarium infested area. The yield advantage CRDI-1 can be partially attributed to its ability to resist or tolerate Fusarium wilt. Higher number of Fov was associated with standard inorganic fertilizer practices (SFP) and relatively lower number of Fov was associated with bio-organic fertilizer fortified with Trichoderma inocula. Plant treated with SFP gave the lowest incidence of Fusarium wilt, plant mortality and highest seedcotton yield. The pre-determined levels of disease incidence of Fusarium wilt at various crop stage exerted significant effect on the seedcotton yield of cotton varieties. For a variety resistant or tolerant to Fusarium wilt like CRDI-1, as the infection increase yield loss increases. Such loss can be explained by the high disease incidence at the seedling, boiling and flossing stages which can be best described by the following models: Y = 9.08 + 0.868 X1, Y = 11.40 + 0.737 X4 and Y = -2.65 + 1.052 X5, where Y is percent seedcotton yield loss and X1, X4 and X5 are disease incidence at seedling, bolling and flossing stage, respectively. For a non-tolerant variety such as UPL-C2, the relationship was best described by Y = 7.19 + 0.871 X1 and Y = 10.00 + 1.072 X3, where X1 and X3 are the incidence at seedling and flowering stage, respectively. The single-point and multiple-point models, which were derived using least square regression techniques proved useful in the satisfactory estimation of seedcotton yield from disease incidence. Thus, these can now be used to estimate seedcotton yield and yield losses caused by Fusarium wilt