Changes in Production Practices Used for Disease Management in Blueberry Nurseries in Georgia, USA, Over a 15-year Period

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.