On the Eastern Shore of Virginia, potato growers plant potatoes in early spring for summer harvest. Fungicide dusts have been typically used to protect the potato seedpiece from infection when planted in cool, wet soil in the early spring. Protection of the seed piece should result in healthier stands of potatoes and higher yields at harvest. Trials were conducted in 2003 and 2004 to examine some of the newer fungicide dust treatments and to compare and combine them with in-furrow sprays of Amistar or Ridomil Gold for the control of Rhizocotonia solani, and bacterial soft rot caused by Erwinia carotovora subsp carotovora. Results presented here are for selected treatments that were evaluated in both years. These studies contained other treatments - for more information call Christine Waldenmaier (757) 414-0724.
|Treatment||2003 Results||2004 Results|
|Yield cwt/A||% Rot at harvest||Yield cwt/A||% Rot at harvest|
|Quadris (Amistar) in-furrow||292 a||2 c||222 a||13 a|
|Ridomil Gold in-furrow 0.42 fl oz/1000 ft row||288 a||3 bc||180 abc||5 a|
|Moncoat Dust 12 oz/100 lb seed||285 a||7 abc||175 abc||6 a|
|Maxim Dust 8 oz/100 lb seed||266 ab||4 bc||186 ab||12 a|
|Maneb Dust 16 oz/100 lb seed||273 ab||12 a||132 b||19 a|
|Untreated Control||237 b||9 ab||152 bc||15 a|
2003 Results: Seed that did not emerge 27 days after planting (DAP) were dug up and examined for decay. All treatments had significantly less soft-rotted seedpieces than the untreated control. Quadris was the only treatment to significantly decrease the percentage of rotten tubers at harvest when compared with the control. Total yield was significantly increased by Moncoat, Quadris in-furrow, and Ridomil Gold in-furrow when compared to the untreated control
2004 Results: Overall, only 3% of the seed pieces did not emerge and of these only 21% were infected with soft rot bacteria. This infection could not be correlated with any particular treatment. Ten stems taken randomly from each plot were evaluated for Rhizoctonia infection on 7/8. Amistar (Quadris) in-furrow and Maxim both reduced lesion length significantly when compared with the untreated control, but not significantly more than any other treatment. Amistar (Quadris) in-furrow increased total yield significantly when compared with the untreated control and Maneb treatment, however, marketable yield and percent U.S. #1 potatoes did not differ significantly by treatment.
Originally printed in Virginia Vegetable, Small Fruit and Specialty Crops – January February 2005.
Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Interim Administrator, 1890 Extension Program, Virginia State University, Petersburg.
August 18, 2009