Biological control of Corynespora leaf fall disease in rubber by endophytic Trichoderma spp. under field conditions

Abstract

Thailand, the leading producer of rubber, is currently grappling with Corynespora leaf fall disease, a condition caused by Corynespora cassiicola (Berk. & Curt.) Wei., leading to defoliation and significant yield losses. In this context, 74 endophytic Trichoderma strains isolated from the foliage of healthy rubber trees were assessed for their antagonistic capabilities against C. cassiicola under controlled laboratory conditions. Specifically, isolates of T. atroviride (1 strain), T. asperellum (4 strains), T. hamatum (4 strains), T. harzianum (4 strains), and T. viride (2 strains) were identified based on their pronounced antagonistic potential, as determined through detached leaf and dual culture assays. These isolates were further evaluated for their disease control efficacy under greenhouse conditions. Among the evaluated Trichoderma strains, T. harzianum KUFA 0760 was observed to exhibit significant antagonistic effects in mitigating Corynespora leaf fall disease, achieving a 49.27% reduction in disease incidence tested by the detached leaf method. This was closely followed by T. asperellum KUFA 0754 and T. harzianum KUFA 0762, which suppressed disease severity by 44% and 45%, respectively. These findings warranted the selection of these strains for subsequent determination of their biocontrol efficacy against the disease under field conditions. In these trials, T. harzianum KUFA 0762 emerged as the most effective, leading to a 36–40% reduction in disease prevalence, while T. harzianum KUFA 0760 achieved a 27% reduction in disease severity. Contrastingly, the application of carbendazim was found to have the highest efficacy, resulting in a 57–59% decrease in disease incidence. Additionally, all tested Trichoderma strains demonstrated compatibility with the recommended fungicide for this disease, mancozeb, at a concentration of 3000 ppm. The outcomes of this investigation underscore the significant biocontrol potential of endophytic Trichoderma spp. against rubber tree diseases. The results advocate for the utilization of such biocontrol agents as either standalone alternatives to chemical fungicides or as part of an integrated pest management strategy, in combination with fungicidal treatments, for the effective control of Corynespora leaf fall disease.