Since the 2000s, production of pitahaya (Hylocereus spp.) has increased significantly in South Florida. However, very limited information is available on the main diseases affecting this crop, particularly in regard to disease epidemiology and economic impact on the commodity. In this study, we surveyed five local pitahaya orchards and documented the most prevalent diseases and their causal agents. Three genera of fungal pathogens (Neoscytalidium, Alternaria, and Colletotrichum) were the major groups associated with symptoms on pitahaya cladodes (stems) during the early growing season. Among these, N. dimidiatum was identified as the most prevalent pathogen, with an overall isolation frequency of 29.8% (range, 13.9 to 47.2%). Hence, the temporal progress of N. dimidiatum stem canker infection was monitored and the relationship between stem canker intensity (incidence and severity) and fruit canker incidence was investigated. A significant positive correlation was found between fruit canker incidence and the standardized area under the disease incidence or severity curve on cladodes, suggesting that high stem canker intensity in the early season may contribute to high fruit canker incidence and thereby impact the aesthetic and market value of fruits. In vitro assays showed that both conidial germination and mycelial growth of N. dimidiatum are positively correlated with increasing temperature, with a maximum growth area at 32°C. This finding suggests a higher risk of infection, under an environment with high temperatures, which is common in South Florida. Data obtained in this study represent baseline knowledge for the future development of integrative management programs for controlling major diseases of pitahaya in South Florida.

The Corynespora leaf fall disease of rubber trees, caused by the necrotrophic fungus Corynespora cassiicola, is responsible for important yield losses in Asian and African plantations, whereas its impact is negligible in South America. The objective of this study was to identify potential antagonists of C. cassiicola among fungal endophytes (i.e., Pestalotiopsis, Colletotrichum, and Trichoderma spp.) isolated from wild and cultivated rubber trees distributed in the Peruvian Amazon. We first tested the endophytes in dual in vitro confrontation assays against a virulent C. cassiicola isolate (CCP) obtained from diseased rubber trees in the Philippines. All Trichoderma isolates overran the CCP colony, suggesting some antagonistic mechanism, while species from the other genera behaved as mutual antagonists. Trichoderma isolates were then tested through antibiosis assays for their capacity to produce growth-inhibiting molecules. One isolate (LA279), recovered as an endophyte from a wild Hevea guianensis specimen and identified as Trichoderma koningiopsis, showed significant antibiosis capacity. We demonstrated that LA279 was also able to endophytically colonize the cultivated rubber tree species (H. brasiliensis). Under controlled laboratory conditions, rubber plants were inoculated with three Trichoderma strains, including LA279, in combination with the pathogenic CCP. Results showed that 1 week preinoculation with the endophytes differentially reduced CCP mycelial development and symptoms. In conclusion, this study suggests that T. koningiopsis isolate LA279—and derivate compounds—could be a promising candidate for the biological control of the important rubber tree pathogen C. cassiicola.

Laurel wilt (LW), caused by Raffaelea lauricola (RL), is a vascular fungal disease affecting species in the Lauraceae that has rapidly spread across the United States. This disease has caused significant tree losses in natural forests and Florida’s commercial avocado orchards. RL spreads through ambrosia beetle vectors and root grafts. Early detection and eradication are recommended to contain outbreaks. Therefore, rapid diagnosis is key for the timely implementation of mitigation strategies. Current LW diagnosis can take up to 10 days and involves pathogen isolation and the amplification of two microsatellite regions. To reduce diagnosis time, we optimized the standard PCR-based detection technique and assessed its potential use in the testing of woody samples. We further screened the microsatellite primers IFW and CHK on a higher number of fungal taxa as well as 11 host genotypes. Sensitivity was evaluated using RL-DNA at different concentrations in pure and mixed solutions. There was no cross-amplification in non-RL species. Both primers amplified all tested RL strains (100); however, the IFW primers were more sensitive than the CHK primers. Using the IFW primers, we detected RL in 89% of sapwood samples (76/85). This protocol provides a rapid and effective molecular-based approach that reduces the diagnostic time from 10 days to 24 h. This method can be an important tool for diagnostic laboratories. Altogether, our data and fungal collection, represent a robust foundation for future transferability of this protocol to more sensitive detection technologies (qPCR, LAMP) and for its application to samples from diverse origin (beetles, roots).