Dispersal of Colletotrichum acutatum sensu lato conidia from infected citrus and strawberry under simulated rainfall and different laminar and turbulent wind speeds

Authors: GAMA, ANDRE - University Of Florida; DE GODOY GASPAROTO, MARIA - Universidad De Sao Paulo; POOLE, GAVIN - North Carolina State University; Bock, Clive; Gottwald, Timothy; AMORIN, L - Universidad De Sao Paulo; PERES, NATALIA - University Of Florida; DEWDNEY, MEGAN - University Of Florida

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2024
Publication Date: 1/29/2025
Citation: Gama, A.B., De Godoy Gasparoto, M.C., Poole, G.H., Bock, C.H., Gottwald, T.R., Amorin, L., Peres, N.A., Dewdney, M.M. 2025. Dispersal of Colletotrichum acutatum sensu lato conidia from infected citrus and strawberry under simulated rainfall and different laminar and turbulent wind speeds. Phytopathology. https://doi.org/10.1094/PHYTO-11-24-0342-R.
DOI: https://doi.org/10.1094/PHYTO-11-24-0342-R

Interpretive Summary: The disease anthracnose fruit rot of strawberry and postbloom fruit drop of citrus is caused by Colletotrichum acutatum. Although the pathogen produces spores, they do not show symptoms in the host flowers or fruit. Dispersal of spores is known to occur in windblown rain. However, wind alone may play a role in dispersal, especially for inoculum surviving on vegetative tissue. Samples of diseased tissue were placed in wind tunnels at known distances downwind from Petri-plates with media. Spores were dispersed up to 15 m in wind speeds greater than 10 m/s. Dispersal in rain splash and wind was limited to short distances, usually within 1 m from the inoculum source. Our data describes how C. acutatum sensu lato conidia spread from inoculum sources on two different infected hosts and different tissues, and for the first time describes how dispersal of C. acutatum secondary conidia occurs from citrus and strawberry leaves in wind. Knowledge of the dispersal of spores of C. acutatum can provide valuable information on epidemic development, and thus approaches for disease management.

Technical Abstract: Species of the Colletotrichum acutatum complex cause postbloom fruit drop of citrus and anthracnose fruit rot of strawberries. C. acutatum produces acervuli in diseased citrus flowers and strawberry fruit, surviving without causing symptoms on vegetative tissues. Dispersal of conidia from acervuli has been extensively studied in strawberry fruit and spatiotemporal analysis has been conducted to study postbloom fruit drop of citrus. Previous studies have suggested that dispersal mechanisms other than windblown rain may be involved in dispersal of conidia of C. acutatum sensu lato. Our hypothesis is that wind alone may play a role in dispersal, especially for inoculum surviving on vegetative tissue. Our objectives were to study the dispersal pattern of C. acutatum sensu lato on strawberry fruit and leaves, and citrus flowers and leaves. We placed inoculum sources in laminar flow and turbulent wind tunnels at known distances downwind from Petri-plates with selective media. The inoculum sources were exposed to different conditions of wind and rain. After we applied the treatments, the Petri-plates were incubated at 25oC and constant light. The number of C. acutatum sensu lato colony-forming units (CFU) on each plate was counted and mean CFU analyzed in relation to distance from the inoculum source. Conidia were dispersed up to 15 m in wind speeds greater than 10 m/s but observed dispersal patterns were not described by the models we tested. A negative exponential model adequately described the dispersal gradient of inoculum downwind, particularly for the dispersal gradient in turbulent wind. Dispersal in rain splash and wind was limited to short distances, usually within 1 m from the inoculum source. Our data describes how C. acutatum sensu lato conidia spread from inocuulum sources on two different infected hosts and different tissues under laminar and turbulent wind flow, and for the first time describes how dispersal of C. acutatum sensu lato secondary conidia occurs from citrus and strawberry leaves. Knowledge of the dispersal of conidia of C. acutatum sensu lato can provide valuable information on epidemic development, and thus approaches for disease management.