Authors
B. A.
Fortnum
,
Professor of Plant Pathology and Physiology, Clemson University, Pee Dee Research and Education
Center, Florence, NC 29506-9706
;
J.
Rideout
,
Assistant Professor of Soil Science, North Carolina State University, Mountain Horticultural Crops Research and Extension Center, Fletcher 28732
;
S. B.
Martin
,
Associate Professor of Plant Pathology and Physiology, Clemson University, Pee Dee Research and Education Center
; and
D.
Gooden
,
Professor of Agronomy, Clemson University, Pee Dee Research and Education Center
ABSTRACT
Float nutrient solution, soilless media, and ambient temperatures were monitored in two tobacco greenhouses with different heating regimes. Water temperatures at seeding were 11°C in an unheated greenhouse and 17°C in a heated greenhouse. Water temperature differences between greenhouses continued over the duration of seedling production. Media and air temperatures varied diurnally, but not float solution. In a greenhouse float system where water temperatures were constant at 15, 20, 25, or 30°C, seedling disease caused by Pythium myriotylum was correlated with float-water temperature and could be described by quadratic equations (R2 = 0.99) with the lowest level of root necrosis at 15°C. Pythium spp.-infected and noninfected seedlings grown in controlled-temperature water baths were transplanted to the field and evaluated for disease development. Previous infection with P. myriotylum, regardless of float-temperature regime, failed to alter yield, leaf quality, or root necrosis (P = 0.05) in field-grown tobacco.
