Phosphorus, nitrogen and potassium nutrition on Calonectria leaf blight in eucalypt plants

Abstract

AbstractCalonectria pteridis causes Calonectria leaf blight (CLB), and consequently severe defoliation in eucalypt plantations, which results in losses in wood volume. To reduce the negative impacts of this disease in eucalypt, this study aimed to assess the application of different doses and combinations of the macronutrients N, P and K on the percentage of symptomatic leaf area (SLA) and defoliation induced by the pathogen. Cuttings of a clone of Eucalyptus grandis were transplanted to pots containing soil that received different dose combinations of N, P and K, according to an incomplete factorial design. At 200 days after transplanting, leaf samples were analysed for N, P and K contents, and then, the plants were inoculated. Forty‐five days post‐inoculation, SLA and percentage of defoliation were quantified. Potassium doses above 75 mg/dm3 of soil significantly reduced SLA and defoliation. The influence of N and P on defoliation was dependent on K doses, but both reduced symptomatic leaf area. The best control of the disease, expressed by decreased defoliation and symptomatic leaf area, was achieved with leaf content of N, P and K of 9.8, 0.8 and 10.4 g per kg leaf, respectively, obtained with doses of 55, 82.5 and 143 mg/dm3of soil, respectively. Therefore, N, P and K nutrition can be a component of an integrated management programme for the control of CLB in eucalypts.