Hazelnut (Corylus avellanaL.) which is intensively grown in the Black Sea region is the most important agriculturalproduct of Turkey. Hazelnut production and quality are negatively affected by several diseases and pests. Powdery mildewis nowadays one of the most common diseases in almost whole hazelnut producing areas. The disease is caused by twodifferent species,Phyllactinia guttata(Wallr. et Lev.) Fr. andErysiphe corylacearumU. Braun & S. Takam. For the last4 years,E. corylacearum, a newly invasive fungus in Turkey, has been caused significant economic losses. In the presentstudy, the efficacy of ammonium, potassium and sodium bicarbonates, and two fungicides were evaluated in field trialsagainst powdery mildew on hazelnuts in Samsun in 2016. The application rates of compounds used in the experimentwere as follows: ammonium, potassium and sodium bicarbonates (Sigma-Aldrich, Seelze, Germany) at 1.5, 3, 4.5 and 6%(w/v); Collis®SC (100g/l Kresoxim methyl +200g/l Boscalid, BASF, Spain) at 30ml/100l and Sulflow®80 WG (Sulphur800g/l, Agrofarm, Turkey) at 400g/100l. Of the compounds tested, except for fungicides, sodium was found to be the mosteffective in controlling the powdery mildew on hazelnuts, followed by potassium and ammonium, respectively. Amongthose three, ammonium bicarbonate was ineffective against fruit infections of the disease. There was also no significant difference between inhibitory effects of 6% sodiumbi carbonate, Collis and Sulflow against the disease (P< 0.05). Inaddition, bicarbonate salts was phytotoxic to hazelnut leaves at concentrations greater than 1.5%. The results indicate that sodium or potassium bicarbonate solutions seems to be a useful biocompatible fungicidefor controlling the powdery mildew on hazelnuts.

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• Evaluation of Inhibitory Effect of Some Bicarbonate Salts and Fungicides Against Hazelnut Powdery Mildew