Efficacy of Minimal-, Moderate-, and High-Input Disease Management Systems for Pierce’s Disease-Resistant Hybrids
Shane Breeden* and Phillip Brannen
*University of Georgia, CAES Campus 324 Hoke Smith Building,
Horticulture Department, Athens, GA, 30602
(shane.breeden@uga.edu)
Pierce’s disease- (PD-) tolerant hybrid winegrape cultivars are an important alternative to Vitis vinifera cultivars in the southeastern United States. While these hybrid cultivars lessen the concern from PD, there is little to no available information on their susceptibility to other grape diseases or tailored disease-management programs specific to these hybrids. Three different spray programs (treatment regimens) were used on five PD-resistant Vitis hybrid cultivars: 07370-84 and ‘Camminare noir’ from the UC Davis PD-resistance grape breeding program, ‘Lomanto’, ‘Blanc du bois’, and ‘Crimson Cabernet’. Regimens tested were: (1) an untreated control; (2) low input (no fungicides with significant powdery mildew activity); (3) moderate input (addition of products with more efficacious downy mildew activity); and (4) high input (additional materials added for rots, powdery mildew, and downy mildew). All cultivars developed downy mildew, though the degree of mildew varied. Powdery mildew did not develop on Blanc du bois or Crimson Cabernet in these trials. Though distinctions in mildew development were observed, all of these PD-resistant hybrids will require a full program for commercially-acceptable rot management. Black rot (Guignardia bidwellii), bitter rot (Greeneria uvicola) and Macrophoma rot (Botryosphaeria dothidea) were prevalent. For all hybrids, fruit rot incidence, measured as area under the disease progress curve (AUDPC), was consistently and substantively lower for the high-maintenance fungicide regimen (p ≤ 0.05). It had been hypothesized that some of these hybrids might provide some resistance to rots due to the inclusion of native grapes in their heritage. Unfortunately, though hybridization with native grape species conferred resistance to Pierce’s disease, it does not allow for use of more economical spray programs as a whole.
Funding Support: Southern Region Small Fruits Consortium
