Splash dispersal of conidia of Fusarium culmorum and Fusarium avenaceum

Splash-dispersal patterns of Fusarium culmorum and Fusarium avenaceum conidia were studied in still air by allowing simulated raindrops, 5 mm in diameter, to fall onto stem bases bearing sporodochia. Splash-dispersed conidia were collected on vertical strips of selective agar (100 × 3 cm) placed at distances 10–100 cm from the source. Colonies of F. culmorum and F. avenaceum were observed at maximum heights of 60 and 45 cm, respectively, and at maximum horizontal distances of > 100 and 90 cm, respectively from the source. Most conidia were found close to the source with 82% of F. culmorum and F. avenaceum colonies counted within a height of 20 cm. Seventy and 80% of F. culmorum and F. avenaceum colonies, respectively, were recorded within a horizontal distance of 30 cm. For cases in which a negative exponential model presented in its linear form could be fitted to the observed horizontal and vertical deposition gradients, half-distances of 10·5–13·6 cm and half-heights of 3·9–11·7 cm were obtained for conidia of F. culmorum . Half-distances of 9·2–16·5 cm and half-heights of 4·4–8·4 cm were obtained for conidia of F. avenaceum . These observations are discussed in relation to the epidemiology of Fusarium diseases of cereals, in particular the role of rain in the upward dispersal of Fusarium inoculum from the stem bases of infected plants or infected stubble to ears of winter wheat.

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