Abstract
The response of three commercial Cavendish banana (Musa AAA) cultivars 'Lacatan', 'Robusta' and 'Valery' and two tetraploids A and B (Musa AAAA) were examined at different localities in sprayed and unsprayed plots. The main criteria employed for judging varietal responses were percentage leaf spotting, mean number of youngest leaf spotted and mean number of green leaves. 'Robusta' and 'Valery' were ranked as susceptible while 'Lacatan' was found to be highly susceptible. Among the tetraploids, A was regarded as partly resistant, and B as highly resistant, though not immune. Response varied with season and site of planting. In situations of low disease pressure, 'Robusta' and 'Valery' were similarly affected and 'Lacatan' showed marginally more leaf spotting. At other sites, ‘Valery’ was consistently less affected than ‘Robusta’. It is shown that cultivars with similar genetic constitution could show differing amounts of disease if the rates of leaf mergence are different. 'Lacatan' is the tallest member of the Cavendish group with the slowest rate of leaf emergence. It is suggested that factors such as height of plant, rate of leaf emergence, length of leaf etc. may afflict aerodynamics of the leaf, impaction of leaf spot spores and amount of disease.
