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CORESTA Meeting, Agronomy/Phytopathology, Rovinj, 2009, AP 08

A best management system reduces bacterial wilt of flue-cured tobacco

FORTNUM B.A.; PETERSON P.D.; GOODEN D.
Clemson University, Dept. of Entomology Soils and Plant Sciences, Pee Dee REC, Florence, SC, USA

Bacterial wilt caused by Ralstonia solanacearum is an extremely damaging disease of flue-cured tobacco in the southeastern USA. During a bacterial wilt epidemic in 2004, this disease accounted for over $4,000,000 in crop losses and 72% of all disease losses in South Carolina tobacco fields. Mechanization in flower (topping) and leaf (multipass harvester) removal has contributed significantly to the spread and severity of bacterial wilt. The objective of the present trial was to develop a best management system to reduce disease by eliminating mechanical transmission of R. solanacearum in flower and leaf removal and by enhancing disease control through the use of crop rotation, host resistance and soil fumigation. The experimental design was a randomized complete block 3-factor factorial where main effect was rotation, subplot effect was the management system (standard vs. best management) and sub-subplot effect was soil fumigation. The test was repeated in time. Use of a best management system (hand topping and hand- leaf harvesting) reduced percent disease and increased yield ( P = 0.01, and 0.002, respectively) over tobacco that was mechanically topped and harvested. Use of a resistant variety (Ox 207) and soil fumigation reduced percent disease and increased crop yield (P ≤ 0.01) over a susceptible variety (K 326) and a non-fumigated control ( P ≤ 0.01). Rotation to soybeans reduced disease incidence and increased yield ( P ≤ 0.02). Data showed that if mechanical transmission of R. solanacearum could be reduced bacterial wilt could be controlled with standard treatments such as rotation, host resistance and soil fumigation. Elimination of mechanical transmission of R. solanacearum averaged across treatments reduced disease 54% (14 vs. 30%) and increased yield 40% (1691 vs. 2360 Kg/ha). The use of new topping and harvesting equipment will be discussed.