Basal stem rot (BSR), caused by Ganoderma spp., is one of the most important emerging oil palm diseases in Colombia, and is restricted to two oil palm production areas in the country. To identify the causal agent of the disease, basidiocarp of oil palms affected by BSR were used to prepare isolates, and their pathogenicity was then assessed in pre-nursery plants. Four-month-old oil palm seedlings were inoculated with rubber wood (Hevea brasiliensis) blocks colonized with dikaryotic mycelia of Ganoderma. The incidence, severity, and symptoms of the pathogen were assessed. A multiregional analysis (ITS, rpb2, and tef1-α) was carried out to identify the isolates; all isolates were determined to be Ganoderma zonatum. Phylogenetic analyses with the three regions yielded concordant phylogenetic information and supported the distinction of the isolates with high bootstrap support. Seven isolates (CPBsZN-01-29, CPBsZN-02-30, CPBsZN-03-31, CPBsZN-04-34, CPBsZN-05-35, CPBsZN-06-36, and CPBsZN-07-38) were pathogenic in oil palm, with incidences greater than 90% and a maximum severity of 34%, and the highest severity index was found in isolates CPBsZN-03-31, CPBsZN-04-34, and CPBsZN-06-36. The pathogen was recovered from inoculated oil palms in all cases. This study reveals the pathogenic association of Ganoderma zonatum with BSR in Colombia.

Colombia is the Latin American country with the second-largest area planted with OxG hybrid cultivars, covering more than 120,000 hectares Various health problems can affect yield, especially those affecting fruit. Since 2021, white fruit rot has been reported in the northern, central, and southwestern palm-growing areas. Therefore, the objective of this study is to identify associated symptoms and their causal agent. To this end, a total of six locations in the three palm-growing regions were visited, and 36 samples of affected fruits were collected to obtain microorganisms. These microorganisms were inoculated into detached fruits under in vitro conditions, and seven isolates were inoculated into bunches in the field. They were morphologically and molecularly characterized by partial sequencing of the ITS and TEF1 regions. Symptoms of white rot were observed, starting from the base of the fruit to the apex, with the development of a cottony mycelial mass, followed by the formation of sclerotia. A total of 33 organisms were obtained, 30 isolates identified as Agroathelia rolfsii, one Fusarium sp., one Rhizoctonia sp., and one Pestalotiopsis sp. isolate. The Agroathelia isolates exhibited white, cottony growth adhering to the surface of the PDA culture medium. After four days of growth, they developed globose to ellipsoid sclerotia (average 1.00 ± 0.26 (0.46–2.20 mm)). These were initially white and turned brown as they developed, with the average number of sclerotia per plate ranging from 4 to 449 (n = 6). In the in vitro pathogenicity test, only A. rolfsii isolates were pathogenic, with a 100% incidence, an average severity ranging from 10 to 40% infection, and a range of 10 to 100%. In field inoculations, 100% of the inoculated bunches exhibited symptoms similar to those observed under natural field conditions. In all cases, the pathogen was recovered, fulfilling Koch’s postulates and confirming that A. rolfsii is the causal agent of white fruit rot. This constitutes the first record of Agroathelia rolfsii in oil palm in Colombia.

Basal Stem Rot (BSR), caused by Ganoderma spp., is one of the most important emerging diseases of oil palm in Colombia and is so far restricted to only two producing areas in the country. However, despite the controls established to prevent its spread to new areas, containment has not been possible. This study aimed to understand BSR’s propagation mechanisms and related environmental conditions by measuring Ganoderma basidiospores’ concentrations at various heights using four 7-day Burkard volumetric samplers in a heavily affected plantation. Meteorological data, including solar radiation, temperature, humidity, precipitation, and wind speed, were also recorded. Analysis revealed higher basidiospore concentrations below 4 m, peaking at 02:00 h, with increased levels towards the study’s end. Spore concentrations were not directly influenced by temperature, humidity, or precipitation, but showed higher releases during drier periods. A significant correlation was found between wind speed and spore concentration, particularly below 1.5 m/s, though higher speeds might aid long-distance pathogen spread. This study highlights the complexity of BSR propagation and the need for continued monitoring and research to manage its impact on Colombia’s oil palm industry.

Reader Q: There was no morphological information provided for the isolated specimens, and so it is not known if they are even Ganoderma