Diagnóstico del complejo mancha de asfalto en el cultivo de maíz en el Altiplano Central de Guatemala

Tar spot complex (TSC) is a corn disease associated with the presence of three fungi: the first two pathogens being Phyllachora maydis and Monographella maydis, and the hyperparasite of the stromas of P. maydis known as Coniothyrium phyllachorae. This disease affects the yield of the crop, which can sometimes lead to total loss. It has predominated in tropical areas, characterized by high temperatures and high relative humidity. However, since 2015, there have been reports in the United States, Mexico and Ecuador of the presence of P. maydis in temperate to cold corn production areas. In this context, to determine the presence of pathogens associated with TSC in temperate climate areas, 48 corn fields in the department of Chimaltenango were evaluated during the second half of 2022. In each field, the incidence and degree of infection were evaluated. In 13 locations of Chimaltenango, the presence of P. maydis stromas (shiny black spots scattered on the leaf) was detected, as well as the formation of “fish eyes”. The incidence ranged between 10 and 100 %, with a degree of infection between moderate and strong, according to the scale used. It was confirmed that at least one of the pathogens associated with the TSC , P. maydis, is present in the corn production areas of the central highlands of Guatemala.