Honeysuckle (Lonicera japonica Thunb.), a widely distributed perennial in China, has been affected by a highly infectious powdery mildew since 2023 at Hebei Agricultural University (38°05′N; 115°48′E). Infected leaves developed gray-white mold followed by black spots, resulting in defoliation, and by May 2025, all 32 plants exhibited symptoms (100% incidence). Diseased leaves were examined morphologically. Mycelium amphigenous, thin, effuse. Conidia cylindrical to cylindrical-oval. Conidiophores are mostly single, occasionally two or four on a mother cell, straight or slightly flexuous at the base of foot-cells, and producing conidia singly, with a Pseudoidium germ tube type. Chasmothecia dark brown, spherical, 75–124 μm (n=50), scattered to subgregarious, with 6–17 (n=50) dichotomously branched, erect appendages 1.3–2.0 times the diam, 8–21 μm (n=50) wide at base, narrowing to recurved or straight pale tips. Asci 3–8 (n=50), short-stalked to subsessile, 4–8-spored (n=50). Ascospores subhyaline, ellipsoid-ovoid, 8.4–11.5 × 4.2–5.8 μm (n=50), consistent with Erysiphe lonicerae anamorph (Choi et al. 2023). To further confirm the identification, total DNA was extracted, the isolates were named XXY and cloned by PCR for sequencing of the internal transcribed spacer ITS1/ITS4 (5′-TCCGTAGGTGAACCTGCGG-3′/5′-TCCTCCGCTTATTGATATGC-3′) (White et al. 1990) and the translation elongation factor 1-alpha EF1-α (5′-ATGGGTAAGGAGGACAAGAC-3′/5′-GGAGGTACCAGTCATCATG-3′) regions (Alves et al. 2004). The ITS (PV590655) and EF1-α (PV639325) sequences showed 100% (624/624 bp) and 99% (605/605 bp) identity, respectively, to the ex-type strain E. lonicerae MF623858. Based on morphological and molecular data, the pathogen was identified as Erysiphe lonicerae. Pathogenicity was confirmed through inoculation by pressing infected leaves onto 10 healthy leaves, with 10 non-inoculated leaves as controls, all maintained at 18–25°C in a greenhouse. After 10 days, all inoculated leaves showed symptoms with fungal morphology and the PCR amplicon sequence using primers ITS1/ITS4 was identical, fulfilling Koch’s postulates. Erysiphe lonicerae was previously reported on honeysuckle in Shandong (Kong et al. 2009), Guangxi (Ou et al. 2011), and Guizhou (Cui et al. 2023). This is the first report in Baoding, Hebei, China, aiding future disease management.
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