Survey sampling of 18 blueberry nurseries propagating softwood cuttings was conducted in 2007 and 2008 to determine which soilborne plant pathogens were most prevalent in commercial blueberry propagation systems in southern Georgia. Samples were collected four times: June (early), September (mid), and October (late) in the 2007 growing season, with additional sampling of overwintered cuttings in April 2008. This survey revealed that Calonectria ilicicola (Cylindrocladium parasiticum), causing Cylindrocladium root rot, is a primary pathogen of blueberry cuttings in southern Georgia. The organism was isolated consistently during all four survey dates with a cutting-level incidence of 3.6, 10.2, 36.4, and 14.3% in the first through fourth samplings, respectively. Rhizoctonia spp. were recovered less frequently and were only present during the first (10.9% cutting-level incidence), third (4.6%), and fourth survey dates (3.6%), while the Oomycetes Pythium and Phytophthora were detected only on the second survey date. Fusarium spp. were isolated commonly (29.1% incidence in the first, 12.2% in the second, 18.2% in the third, and 7.1% in the fourth sampling), but pathogenicity remains uncertain. Across all survey dates, Calonectria, Rhizoctonia, Oomycetes, and Fusarium were recovered at least once from 41.2, 17.6, 0.1, and 82.4% of nurseries surveyed, respectively. When nursery-level pathogen presence-absence data collected from this survey was analyzed in relation to a survey of production practices used by these same propagators, the practice of reusing growth media was found significantly associated with Calonectria presence.

Surveys of blueberry [rabbiteye blueberry (Vaccinium virgatum) and southern highbush blueberry (Vaccinium corymbosum interspecific hybrids)] nurseries in the State of Georgia, USA, were conducted in 2007 and 2022 to determine the prevalence of and associations among propagation practices, especially related to disease management. As indicated by the reduction in surveyed nurseries in 2022 (7) compared with 2007 (18), the Georgia blueberry nursery industry has consolidated. However, cultural disease management practices have generally improved in these remaining nurseries. In 2007, in nurseries where cuttings were grown in containers, 77.8% reused containers and 66.7% did not sterilize them before use. The growing medium [pine (Pinus sp.) bark] was reused for subsequent production cycles in 29.4% of nurseries, although such reuse of media tended to be associated with production in beds as opposed to containers (P = 0.08). Nurseries used well water in 88.2% and pond water in 11.8% of cases. Cuttings were grown on benches (vs. the ground) in slightly fewer than half of the nurseries. In contrast, all nurseries surveyed in 2022 grew their cuttings in containers, used well water, and had increased bench use, albeit only slightly. Although all nurseries reused containers, only 28.5% did not sterilize containers before use, and only 14.3% of nurseries reported reusing media. Most nurseries surveyed in 2007 (83.3%) were on a routine, calendar-based fungicide program using a.i. targeted primarily against aboveground diseases (blights and leaf spots) and secondarily against soil-borne water molds (Phytophthora and Pythium species of the Oomycetes class). In contrast, 42.8% of those surveyed in 2022 were on a 2- to 3-week spray schedule, 42.8% used fungicides on an as-needed basis, and 14.4% were on a monthly schedule, indicating that fungicide scheduling varied dramatically among the remaining nurseries.

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