Evaluación de la sensibilidad de Phytophthora infestans (Mont) Bary al fungicida Oxatiapiprolin

The management of aggressive strains of Phytophthora infestans is a challenge for Mexico, so the objective of study proposed to validate and monitor the efficacy of (Oxatiapiprolin), against the sensitivity of P. infestans micropopulations, isolated from the field. A modified protocol with leaf discs and five concentrations of the fungicide at a pressure of 1.2 bar was tested against a severe late blight isolate from the Toluca Valley, State of Mexico. The fungicide showed an inhibitory effect on a mixed isolate of P. infestans under in vitro conditions, compared to the first five concentrations used in the test (1-0.0016 ppm). It was observed that at a higher concentration, there was an increase in the sensitivity of the pathogen and less damage to the tissue. After 5th concentration, less than 25% of tissue was affected (0–2.6 mm) compared with the damage in control (13 mm) (>95%), when the fungicide was not applied. The mean inhibition (EC50) is high calculated at approximately 0.00034 mgL-1 of the fungicide, which inhibits 50% of the growth of the pathogen.