Protection Methods

- During cultivation

No fungicides are currently registered for this use in France.

In case of leaf-harvested tobacco, the plant parts remaining in the field and especially the stems should not be crushed and buried in the soil. This practice contributes towards maintaining the fungus in the plot.


- Next crop

Fungus free seeds should be used.

Avoid re-establishing a crop in a plot where the disease has been severe, and provide a balanced fertiliser (definitely not excessive in nitrogen, but with adequate levels of potash and phosphate). Planting density may be slightly reduced in order to promote ventilation of plants and thus reduce the relative humidity under the crop canopy. Bud removing should be perfectly controlled, as well as the activities of root-knot nematodes (see the fact sheet) , if they are observed in the field.

Several sources of resistance to Alternaria alternata have been described: one from a cigar tobacco cultivar Beinhart 1000-1, which is conferred by a single gene. Its use raises some problems, especially in the case of Virginia tobacco. It is in fact associated with delayed maturity which is detrimental to the quality of the leaves. In order to find a partial solution, breeders have developed heterozygous varieties for this gene (a strategy developed in Zimbabwe); quantitative resistances are found in several American cultivars. A significant number of American varieties are more or less tolerant to brown spot, thanks to the gradual accumulation of several resistance factors.