Impacto Económico Asociado Con Los Daños De Tizón Foliar En La Calidad De La Semilla Del Zacate Buffel En El Centro De Sonora, México

The fungus Pyricularia grisea causes a disease in buffelgrass known as leaf blight and induces serious damage to the plant that affects forage production, nutritional quality, and seed production and quality. The study was carried out during the summer of 2019 in three cattle ranches in Carbó, Sonora with the objective of evaluating the intensity of Pyricularia grisea damage in buffelgrass pastures and its economic impact on the quality of the seed and the consequent seeding costs associated with pathogen damage. Variables evaluated in the study were: degree of leaf blight damage, seed viability, germination, purity, percentage of live pure seed, kilograms of commercial seed required for sowing, and cost of seed affected by various intensities of blast damage. The number of plants affected and not affected by the fungus was determined in four 20 x 20 meters plots in each ranch. In each plot, the degree of damage to all the plants was quantified and categorized using four damage intensities as treatments: (1) No damage, (2) Light damage, (3) Moderate damage, and (4) Heavy damage. The experimental design used was completely randomized with 4 treatments and four repetitions in each ranch. All variables evaluated were analyzed separately and subjected to a simple variance analysis, using Duncan's multiple range test for the comparison of means (P<0.05). The results show that the quality of the grass seed is reduced by the effect of leaf blight damage, since the viability of the seed is reduced from 8.6 to 35.3%; germination is reduced from 5.7 to 21.6%; purity is reduced between 0.7 and 17%; viable pure seed (PVS) is reduced between 5.6 and 24.0%. Consequently, the number of kilograms of commercial seed required for planting the species increased between 1.09 and 10.32 kg/ha. This is equivalent to the cost of additional seed purchases increasing between 14.7 and 140.4%, which is equivalent to paying an additional $97.8, $454.2, and $928.2 pesos per hectare if the seed used in sowing comes from areas with light, moderate or intense damage, respectively. It is concluded that foliar blight affects the quality of the buffelgrass seed, so it is recommended not to harvest seed from areas affected by the fungus, which will increase the chances of planting failure and/or avoid unnecessary expenses in planting buffelgrass when seed used was harvested in blast affected pastures.