Control of Peronospora schleidenii Unger of onion in Ukraine.
The efficacy of Ridomil Gold MC (2.5 kg/ha), arachidonic acid (0.002 litre/ha), Mycosan B (10.0 litres/ha), and Ridomil Gold MC (1.5 kg/ha) + arachidonic acid (0.001 litres/ha) + Mycosan B (5.0 litres/ha) against downy mildew (P. schlidenii [P. destructor]) in onion (cv. Skwyrska) was evaluated in Ukraine during 2003-05. Ridomil Gold MC + arachidonic acid + Mycosan B was highly effective against downy mildew (biological efficiency of 89.2% on the first year and 87.8% on the second year). The treatments had no significant effects on plant dry matter and vitamin C [ascorbic acid] contents, but had significant effects on peroxidase activity. N and K metabolism was also affected by the treatments, as evident in the increase in nitrate (by 78-84%) and glutamine (by 7-8%) contents, and reduction in K (by 29-32%), and arginine, tyrosine and leucine (by 3.8-7.2%) contents. The fungicides had no significant effects on the contents of isoleucine, threonine, lysine, phenylalanine, cystine, histidine, asparagine, serine, proline, glycine, alanine, tryptophan and methionine.