Bell Pepper (Capsicum annuum L.) is one of the top produced vegetable crops in Georgia. In mid-August 2025, two transplant trays (200 cells/tray) of pepper seedlings (cvs. Autry and 9325) with severe leaf spot symptoms were received at the University of Georgia’s Tifton Plant Disease Clinic from a commercial greenhouse facility in Moultrie, Georgia. Foliar symptoms included small brown spots to larger necrotic lesions with gray to white center and dark-brown edges. As foliar symptoms progressed, yellowing and abscission of leaves were also observed. More than 75% of the seedlings on each tray were symptomatic. To identify the causal agent, small symptomatic leaf tissues were excised from the lesion margins, surface sterilized with 10% bleach solution for 2 min, rinsed in sterile water, dried in a sterilized paper towel and then plated onto a potato dextrose agar (PDA) medium. After 4-5 days of incubation in dark at 28°C, circular to irregular, gray fungal colonies with lighter gray to white margins were consistently isolated with 100% frequency. Conidiophores were dark and septate with swollen tips. Conidia were brown, dark, oblong measuring 20-50 µm × 12.5-30 µm (n=20) with both longitudinal and transverse septa and were found at the end of the conidiophores. Colony and conidial morphology were consistent with Stemphylium spp. descriptions (Woudenberg et al. 2017). One pure isolate, AJ293-2025, was selected for molecular identification. The internal transcribed spacer region of rDNA was amplified with primers ITS5/ITS4 (White et al. 1990). The glyceraldehyde-3-phosphate dehydrogenase (gpd) was also amplified with primers GPD1/GDP2 (5′-CAACGGCTTCGGTCGCATTG-3′/5′-GCCAAGCAGTTGGTTGTG-3’), as described by Berbee et al. (1999). The ITS sequence showed 100% identity to strain CBS: 122803 (type culture; GenBank Accession: MH863236) of Stemphylium lycopersici. The gpd sequence showed 100% identity to strain 01 (GenBank Accession KR911809) of Stemphylium lycopersici (Sun et al. 2016). The ITS and gpd sequences of isolate AJ293-2025 were submitted to GenBank under the accession numbers: PX959576 and PX963832. To complete Koch’s postulates, two 2-month-old healthy pepper seedlings (cv. Aristotle) were spray-inoculated until run-off with the combined mycelial and conidial suspensions of the Stemphylium isolate (6.75× 104 spores/mL; 10 ml per plant). Two healthy seedlings (cv. Aristotle) sprayed with sterile water were used as controls. All seedlings were maintained in a growth chamber at 25°C, 80% relative humidity and 16 h light/8 h dark light period. The experiment was conducted twice. After 5 days post inoculation (DPI), the inoculated plants showed brown spots on the leaves which eventually turned into larger spots with a gray center and dark brown margin, consistent with those observed in naturally infected plants. The fungus was successfully reisolated from the symptomatic tissue and confirmed as Stemphylium lycopersici based on both morphological and molecular identification as described above. The plants used as controls developed no symptoms. Stemphylium lycopersici has been previously reported in pepper in China (Xie et al. 2019), Taiwan (Sun and Huang 2022) and in India (Anusha et al. 2024). To our knowledge, this is the first formal report of Stemphylium leaf spot of pepper in Georgia. This observation suggests that effective management strategies should be explored to prevent the disease and mitigate potential yield losses in Georgia.
Pandey et al. (Sun,) studied this question.