P-483 - Prevalence and Distribution of Oomycetes in Massachusetts Cranberry Bogs: Implications for Root Rot and Disease Management

Root rot symptoms have been increasingly reported in Massachusetts cranberry bogs over the past five years. While Phytophthora and Pythium species have been isolated from symptomatic bogs, their precise role in disease development, impact on yield, and species distribution remain unclear. To address this knowledge gap, a comprehensive survey was conducted in 2024 across southeastern MA to assess the prevalence of oomycete species in cranberry bogs. The study utilized ImmunoStrip assays, soil baiting with vials containing selective PARP media (Corn Meal Agar with pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene) deployed for 4–5 weeks, and field water testing. Samples from 50 bogs were analyzed, with root tissues examined using ImmunoStrip assays, selective media plating, and DNA sequencing of isolates, while vials and water samples underwent DNA extraction and PCR analysis. Results confirmed the widespread presence of oomycetes, with 56% of root samples, 73.9% of soil baiting vials, and 95.5% of water samples testing positive. DNA sequencing identified Phytophthora cinnamomi as the predominant species (61% of isolates), followed by Phytopythium vexans (14%) and Phytophthora drechsleri (9%), along with other oomycetes. While P. cinnamomi and P. drechsleri have been previously reported on cranberry, the impact of other species remains unclear. Future research will focus on evaluating the pathogenic potential and epidemiological significance of these oomycetes, as well as assessing their impact on cranberry yield, to enhance disease management strategies.