CONTROL OF Lasiodiplodia theobromae, THE CAUSAL AGENT OF DIEBACK OF SAPOTE MAMEY [Pouteria sapota (Jacq.) H. E. Moore and Stearn] GRAFTS IN MÉXICO

Abstract

Dieback of sapote mamey [Pouteria sapota (Jacq.) H. E. Moore and Stearn] grafts caused by Lasiodiplodia theobromae significantly reduces the success of grafting in Mexican nurseries. Semi-commercial tests were conducted in a sapote mamey nursery during two grafting seasons to evaluate the effectiveness of a physical treatment (washing) and three chemical treatments (fungicide dip) on scions. Washing reduced disease incidence up to 31 %, whereas chemical treatment reduced it up to 62 %. The combination of washing and thiabendazole dip resulted in an incidence decrease of 81 %. Twelve other fungicides were screened in vitro to evaluate mycelial growth inhibition of L. theobromae. The pre-formulated mix of cyprodinil + fludioxinil was the most effective fungicide with EC₅₀ value of 0.0043 μg mL^-1, followed by pyraclostrobin + boscalid, prochloraz and tebuconazole with EC₅₀ values < 0.1 μg mL^-1, and iprodione and thiabendazole with EC₅₀ values < 1.0 μg mL^-1. This study provides novel information about strategies for controlling L. theobromae infection during the grafting process of sapote mamey and it also showed the effectiveness of several fungicides under in vitro conditions for controlling this plant pathogenic fungus.