Progress 07/01/03 to 12/31/04
Outputs
Fruit of Chardonnay, Cabernet Franc and Merlot were most susceptible to infection by Greenaria uvicola from 6 to 9 weeks after bloom. The optimum temperature and duration of wetting for infection of fruit were 23.7C and 9 hours. Fruit of Vitis vinifera were significantly more susceptible to infection by G. uvicola than French-American hybrids. V. aestavilis Cynthiana was the most resistant cultivar/section to G. uvicola. From early May through mid-September potential vectors of Xylella fastidiosa were trapped in 3 vineyards in the eastern Piedmont and 1 on the northeast coast of NC. The 4 most abundant leafhopper species trapped were Oncometopia orbona, Graphocephala versuta, Paraphlepsius irroratus, and Agalliota constricta. Preserved specimens will be tested for the presence of X. fastidiosa and transmission studies will be conducted using populations of O. orbona and G. versuta. The ability of 4 Alternaria models to predict the occurrence of Alternaria blotch of
apples was examined. None of the models examined accurately predicted either the onset or progression of the disease. Individual disease model attributes revealed that the inoculum level, in addition to the increasing susceptibility of the host, most readily influenced the progression of the disease. A protocol for forensic DNA extraction from plant pathogens was refined to extract DNA from the very minute thyriothecia of Stomiopeltis from fresh apple fruits and selected herbaria specimens. PCR amplification, cloning and sequencing analysis were applied to eleven samples. Stomiopeltis ITS primers St-8F (forward), St 1-8R (reverse) and S1-4F were designed to work with amplification of Stomiopletis from selected samples. In phylogenetic analysis of the Internal Transcribed Spacer region (ITS1) of 3 of the 11 specimens and our 19 Stomiopeltis spp. sequences at the GenBank, sample MOW5 (Sto 7) from multiloculate thyriothecia aligned with S1-10 (M5A MHCR), S1-11 (M5B MHCR), S1-14 (M8A AL)
all with multiloculate thyriothecia. Based on these results two putative new species of Stomiopeltis appear to be associated with the apple sooty blotch complex in the southeastern US. Prophyt, a phosphorus acid based fungicide, in combination with captan provided control of Alternaria mali on Delicious comparable to the QoI standard. The ED50 value of A. mali to boscalid was determined for 36 isolates using two methods: spore germination and mycelial growth on amended medium. The mean ED50 value for the mycelium growth inhibition test had a smaller standard deviation and the test was less labor intensive to perform and evaluate than the spore germination test. Rotations of Cuprofix Disperss (a copper based fungicide) + Microthiol Disperss (sulfur) and a QoI fungicide from the 3rd through 4th cover sprays provided good summer disease control on the cultivar Rome in grower orchards. An organic program, based on sprays of lime sulfur, copper-based products, and sulfur was evaluated at 3
grower locations and provided disease control comparable to the grower standard with the exception of Brooks spot, which was more severe in the organic program. This project will be continued under a new project number.
Impacts
Bitter rot is one of the most important rot diseases of bunch grapes in the temperate and moist growing regions of the United States. Losses of 25% and more have been recorded in some vineyards in NC. However little is known about the susceptibility of grape varieties to bitter rot. Information on the relative susceptibility of varieties of Vinifera and French American hybrid grapes to bitter rot gathered in this project, will be very useful to growers who are intending to plant new vineyards and will serve as a guide to growers who who must manage the disease in established vineyards.
Publications
- Sutton, T. B., Harrison, U.J., and Anas, O. 2004. Disease control on Rome Beauty, 2004. F&N Tests 59:PF003.
- Sutton, T. B., Harrison, U.J., and Anas, O. 2004. Disease control on Golden Delicious, 2003. F&N Tests 59:PF004.
- Sutton, T. B. and Anas, O. 2004. Summer disease control with new and experimental fungicides, 2003. F&N Tests 59:PF005.
- Gonzalez, E. and Sutton, T. B. 2004. Population diversity of Colletotrichum spp. causing Glomerella leaf spot and bitter rot of apples in three orchards located in North Carolina. Plant Dis. 88: 1335-1340.
- Williamson, S.M., Hodges, C.S. and Sutton, T.B. 2004. Re-examination of Peltaster fructicola, a member of the apple sooty blotch complex. Mycologia 96: 885-890.
- Lu, Y., Ma J., Sutton, T.B. and Ypema H. 2004. Comparison of two assay methods for evaluating the sensitivity of Alternaria mali to boscalid. Phytopathology 94S: S63.
- Miranda, J.G. and Sutton T. B. 2004. Factors affecting bitter rot (Greeneria uvicola) fungus infection of winegrape (Vitis vinifera). Phytopathology 94S: S71.
- Sutton, T. B., Harrison, U.J., and Anas, O. 2004. Disease control on Delicious and Golden Delicious in the mountains, 2003. F&N Tests 59:PF002.
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