Fruit‐spot (‘speckle’) of Jamaican bananas caused by Deightoniella torulosa (Syd.) Ellis

Abstract

SUMMARYUsing an automatic volumetric spore trap, variation in the atmospheric spore content of Deightoniella torulosa (Syd.) Ellis, the cause of banana fruit ‘speckle’, has been studied in a banana plantation during the period September 1960‐February 1961. Dry weather was characterized by relatively low daily mean spore concentrations of 50–200 spores/m.3of air. Much higher concentrations (2000–7000 spores/m.3) were recorded shortly after rainfall or periods of under‐tree irrigation.Considerable reduction in concentration occurred after the removal from the plantation of decaying leaves and other banana ‘trash’, such tissues being the major source of inoculum of D. torulosa. Similarly, spore counts in trash‐free plantations were consistently lower than those in ‘dirty’ ones. Although the evidence is not conclusive, since it was not possible to provide controls, it seems likely that good plantation hygiene is a major factor in reducing the air spore content of the fungus.In the plantations, the large conidia of D. torulosa have a short air‐borne phase, probably because sedimentation and/or deposition rates are high. This results in relatively short horizontal dispersal distances.