Pythium Root Rot of Flue-Cured Tobacco Seedlings Produced in Greenhouses: Factors Associated with its Occurrence and Chemical Control

Abstract

Pythium root rot is an economically important disease of tobacco seedlings produced in greenhouses. In a survey conducted in 1998 and 1999, fivePythium species were found to cause Pythium root rot symptoms in tobacco seedlings. In pathogenicity studies the most aggressive species were Pythium volutum and P. myriotylum, although these were not the most frequently isolated species. We conducted studies with potting media from different commercial sources. Media were not found to be a source of primary inoculum for the disease in those studies. Infested trays had the potential to carry inoculum from one season to the next. The fungicides etridiazole, mefenoxam, and azoxystrobin along with acibenzolar-S-methyl and Joy detergent were evaluated for controlling Pythium root rot. Etridiazole and azoxystrobin applied to the float water provided the best control. Accepted for publication 20 July 2012. Published 25 September 2012.

Integrating Host Resistance and Plant Protectants to Manage Pythium Root Rot on Geranium and Snapdragon

“…This higher disease severity and incidence of P. irregulare isolate on snapdragon, and its resistance to mefenoxam may explain the reduced effectiveness of this product compared with the results obtained from geranium. The inability of mefenoxam to limit root rot in tobacco seedlings has been reported in resistant isolates of P. myriotylum (Guti errez et al, 2012). The biological control agent S. lydicus WYEC108 was one of the most effective treatments in limiting disease symptoms caused by P. aphanidermatum, P. irregulare, and P. ultimum on geranium, and P. ultimum on snapdragon.…”

“…Although azoxystrobin was not among the most effective products in this study, disease severity was significantly reduced in azoxystrobin-treated geranium inoculated with P. irregulare, compared with the untreated inoculated control (Table 2). Guti errez et al (2012) showed that azoxystrobin effectively controlled root rot in tobacco seedlings infected with a P. irregulare mefenoxamresistant isolate.…”

Characterization of Pythium spp. associated with root rot of tobacco seedlings produced using the float tray system in Zimbabwe

“…are able to infect a wide diversity of plants, causing seed, root and lower stem rot, as well as seedling damping‐off of many crops (Broders, Lipps, Paul, & Dorrance, ; Martin & Loper, ). Several species including P. aphanidermatum, P. ultimum , P. irregulare , P. spinosum , P. oligandrum, P. splendens and P. myriotylum have been reported on tobacco worldwide (Cartwright, Spurr, & Shew, ; Moorman and Kim ; Gutiérrez, Melton, & Mila, ).…”