Production and prevention of frenching of tobacco grown in the greenhouse

Summary

The induction and elimination of frenching capacity in soils was studied in the greenhouse. It was found possible to induce this physiological disease in tobacco plants grown in normal soils following partial steam sterilization. High counts ofBacillus cereus Frankland and Frankland, the assumed causal agent, also resulted. Lime was added to soil neutrality, together with high dicalcium phosphate and a moderate quantity of cellulose. Growing plants with bottom heat (35°C) was of great aid in shortening duration of tests. Use of a method of successive plantings progressively depleted the soil of nitrogen and was necessary to obtain uniform and reproduceable results. Results with fertilizer ingredients were inconclusive except that low soil nitrogen, low acidity and high phosphate tended to increase frenching. Nitrogen deficiency and frenching symptoms were distinctly different and appeared independently of each other.

The converse experiments at three levels of soil acidity and four of potassium nitrate gave coordinating results. Acidity and abundant nitrate diminished or prevented frenching of the plants, without however eliminating frenching capacity of the soil.