NITROGEN AND POTASSIUM FERTILIZATION INFLUENCES ON INTENSITY OF PEACH LEAF RUST

Abstract

The objective of this work was to evaluate the effect of nitrogen and potassium fertilization on severity and incidence of peach rust on 'Chimarrita' peach trees. The experiment was conducted in a commercial peach 'Chimarrita' (Prumus persica) orchard which was established in 1999 and is located in Lapa - PR - Brazil. A randomized block design, in a sub-divided-plot system, with three blocks, five nitrogen doses (40, 80, 120 and 200 kg.ha -1 of N) and two doses of potassium (55 and 110 kg.ha -1 of K 2 O), used as sub-plots, was used. Urea was used as the nitrogen source, being 30% of the dose applied at bud break, 30% after thinning and 40% after harvesting. KCl was used as the potassium source, being 60% of the dose applied at the beginning of bud break and the remaining after thinning, accordingly to each treatment. Peach rust (Tranzchelia discolor) severity was determined by using a diagrammatic scale, varying from 1 to 10. The incidence of the disease was determined by percentage of symptomatic leaves on marked branches. Potassium fertilization did not interfere on peach rust severity and incidence, neither on defoliation. Increase in nitrogen dose did not influence incidence of peach rust or defoliation but reduced severity of symptoms.