Protection Methods

- During cultivation

When you are faced with an attack of powdery mildew you need to apply chemical treatments rather quickly. Indeed, when conditions are very favourable for the development of this fungus is quite difficult to stop, and therefore it is necessary to intervene early with the following fungicide: penconazole (see e-phy link).

Keep in mind that an efficient treatment must be applied in time, at the right dose, with sufficient volumes of mixture and with an equipment suitable for tobacco. Some of these treatments may be phytotoxic when applied during warm and dry days. They should be used during cloudy and cool periods.


- Next crop

A number of preventive measures may be implemented to reduce the risk of powdery mildew:
- choose carefully the location of the plot so that it is in a rather airy and sunny aerea;

- avoid excessive watering and avoid stagnation of water in the plot; 

- ensure a balanced fertilisation, destroy weeds which act as relays to the parasite in the plot and in its surroundings;

- ban the vicinity of crops that host the parasite;

- harvest the lower leaves as soon as possible.

Today in France, several varieties of Virginia and Burley tobacco types, available to producers, are resistant to powdery mildew. The situation is the same in the countries where the disease is severe like in Zimbabwe, Japan and South Africa. Several species of Nicotiana are resistant to Golovinomyces cichoracearum var. cichoracearum, but only 3 inter-specific hybrids were created between Nicotiana tabacum and N. debneyi, N. glutinosa and N. tomentosiformis. The resistance conferred by these three species seems to be monogenic and only partial. The most used source of resistance until now comes from a Japanese cultivar Kokobu (Kuo-fan). It is controlled by two recessive genes. It provides a very high level of resistance, although some spots are sometimes observed on tobacco seedlings in nurseries.

*The number of pesticides available for a specific use is constantly evolving but the author has nonetheless chosen to include the names of some registered active ingredients at the time of writing these pages. He will try to update this list as and when withdrawals and new registrations are made. When choosing your crop protection method, please refer to legislation prevailing in your country. This remark is also valid for all organic products based on micro-organisms or natural substances.