Protection Methods

- During cultivation

For several years Botrytis cinerea control has been quite difficult because there are a few B. cinerea strains, more or less present in soil, resistant to the main fungicides used to control them. Furthermore, climatic conditions in sheltered nurseries are quite favourable to its development. To reduce its impact additional measures should be carefully implemented.

Shelters enclosing the nurseries must be well ventilated in order to reduce the ambient humidity and, in particular, to avoid the presence of free water on plants. The introduction of a heat shield on the seedlings, such as an agrotextile (nonwoven fabric, mesh fabric), increases the moisture content and decreases the brightness. In the case of severe attacks, it is best to remove it. In the field, irrigation should be done preferably during the morning and early afternoon, never at night, in order to allow the plants to dry up before nightfall.

If the attacks are observed in the nursery, one of the following antibotrytis fungicides may be used : iprodione, pyrimethanil (e-phy link). These fungicides should be used alternately.

In the field, if the collar cankers are observed at the base of plants, ridging may be done to promote the formation of complementary adventitious roots.

In addition to chemical control, other measures are needed. In the nurseries, plant debris should be eliminated rapidly, especially the affected plants on which the fungus sporulate abundantly. Nitrogen fertilisation should also be monitored, specifically in the floating seedbeds. It should not be too heavy (a source of very susceptible succulent tissues) or too low (a source of chlorotic leaves forming ideal nutrient bases for Botrytis cinerea).

- Next crop

To prevent attacks on young seedlings, the shelter walls enclosing the nurseries and equipment used should be disinfected (see the section Nursery and planting diseases).

We will also consider previously reported measures. Preventive fungicide treatments should be carried out early, well before the high density of plants no longer permits to apply a fungicide at the centre of vegetation. Chemical control should take into consideration the phenomena of resistance observed in the shelters. It will be necessary to always alternate the active ingredients.

As soon as the vegetation becomes important, one should be vigilant, especially during overcast periods and at the approach of harvesting of tobacco plants and leaves.