Wilt Disease of Tara (<i>Caesalpinia spinose</i> Molina Kuntz) in Nursery in the Inter Andean Valley of Cochabamba, Bolivia

Abstract

Tara ( Caesalpinia spinose Molina Kuntz) is a native plant of the Bolivian Andes. A number of projects have promoted the cultivation of this species over the last 20 years, in efforts to make use of its medicinal, food and industrial properties. However, as tara plantations have grown, so too has the incidence of disease affecting the species, leading to economic losses. The aim of the present work was to identify the causal agent of wilting in tara, and to determine the incidence of the disease in nursery-grown plants. Three experimental plots (R1-R3) were established in plantlet production bedsat the ESFOR nursery in order to assess the incidence of wilting. Plant spacing was 1 × 1 m. At the two leaf stage, samples of diseased and apparently healthy plants were taken to the laboratory for the isolation of pathogens. Both the apparently healthy and diseased plants gave rise to the same kinds of fungal colony on PDA. Microscopic examination revealed microconidia, macroconidia, phialides and chlamydospores suggesting the causal agent to be Fusarium oxysporum . Over the (up to) 84-day period following thinning, the incidence of wilting for 2010 was R1 = 2.56%, R2 = 3.15% and R3 = 2.22% per 14 days, and for 2013 it was R1 = 1.24%, R2 = 2.45% and R3 = 2.13% per 14 days; the apparent infection rates for 2010 were r R1 = 0.0003/day, r R2 = 0.0003/day and r R3 = 0.0003/day, and for 2013 they were r R1 = 0.0003/day, r R2 = 0.0004/day and r R3 = 0.0003/day. These values are characteristic of monocyclic epiphytic fungi such as F. oxysporum .