“Decay and descending death” new disease of Schizolobium parahybum (Vell.) S.F. Blake (pachaco) in Ecuador

Abstract

Plantations of Schizolobium parahybum (pachaco) in the Ecuadorian Humid Tropics are being affected by the disease “decay and descending death”, whose etiology is unknown so far. The aim was to know the incidence, severity, and symptomatology of the disease and to identify morphologically the fungi associated with diseased trees. A 5-year-old plantation of S. parahybum was studied in the province of Los Ríos, where three rectangular plots of 500 m2 were established. Disease severity was evaluated with a 5-category scale (1=apparently healthy tree, and 5=tree with more than 50% dead tissue). For each plot, three trees were dissected and their tissues were analyzed under three methodological strategies (wet chamber, carrot sandwiches and potato-dextrose-agar (PDA) culture medium).  Disease incidence was low at 1.7% (13 diseased trees ha-1). Diseased trees were found at scale 2, which indicates that they are at an early stage of the disease. Diseased trees showed loss of turgor, paleness and yellowing of leaflets, with young leaves showing reduced size and poor formation. Longitudinal areas of necrosis were observed in the upper third of the stem. The fungi Fusarium sp. 1, Fusarium sp. 2, and Botryodiplodia sp. were isolated and identified, all causing pathogenesis in plants.