In France, the fungus Sclerotinia sclerotiorum affects tobacco late in the cycle, after topping. The problem has been increasing over the last 6-7 years. Rainfall is an important factor for contamination and spread. Symptoms are stem and leaf vein necrosis. At the end of the cycle, sclerotia are observed inside the stem. The disease causes a loss of yield and quality. Few active ingredients are authorised in France and they are preventive only. In order to reduce the pesticide residues and their environmental impacts, alternative methods are being tested.

From 2011 to 2013, experiments were performed at Bergerac, on a highly sensitive flue-cured breeding line in conditions of natural infestation. The tested alternative method consisted of three foliar applications of CONTANS^®WG (Coniothyrium minitans 100 g/kg), 20 days apart, with a dose of 2 kg/ha. The experimental design had randomised complete blocks with four replicates and included an untreated control as well as the reference treatment: two applications of SWITCH^® (Cyprodinil 375 g/kg + fludioxonil 250 g/kg) at a dose of 0.6 kg/ha, at the same time as the last two applications of CONTANS^®WG. Treatments were applied with 300 l/ha of spray, according to good experimentation practices, starting 50 days after transplantation.

In terms of frequency of diseased plants, the alternative method produced results on average similar to the conventional method each year. However, parasitic pressure heterogeneities in natural conditions led us to repeat the experiment for one more year (2014). Furthermore, in 2014, the viability of extracted sclerotia from stems of treated and untreated plants will be checked.

CONTANS^®WG is a product with known efficiency in soil treatment but it is not widely used as a foliar spray. However, this work suggests some interest in using it as a foliar spray. CONTANS^®WG is a living product, storage conditions must be observed for optimal efficiency.