Determinación de Resistencia de la Roña del Manzano Venturia inaequalis al Benomilo en Arteaga, Coahuila, México

Apple leaves and fruits with scab (Venturia inaequalis) symptoms were sampled in 16 orchards grown under conventional production system, in three canyons of the apple growing area of Arteaga, Coahuila, Mexico, in order to determine levels of resistance by the fungus to benomyl. Resistance to the fungicide was observed only in seven orchards; in five of them, the resistant population was low (3-34%), whereas in the other two was high (72-85%). Based on the IC 50 that ranged from 0.12 to 408.6 ppm for the different strains, resistant factors were determined to be from 145 to 3,143. The above observations showed that V. inaequalis population in this apple growing area is made up of susceptible and resistant individuals, and that it is heterogenous with respect to levels of resistance to benomyl.