Splash dispersal of conidia of Mycocentrospora acerina in the field



The dispersal of conidia of Mycocentrospora acerina was studied in caraway field trials. A Burkard spore trap, rotorods, inverted Petri dishes containing sucrose agar and rain gauges were used to trap conidia of M. acerina. Sporulation was stimulated by rainfall (geqslant R: gt-or-equal, slanted2 mm) and moderate temperatures (around 15°C). Solar radiation had a negative effect on sporulation. Hardly any conidia were found in the spore traps on rainless days. Short distance (leqslant R: less-than-or-eq, slant9 m) spread of M. acerina is mainly caused by splash dispersal of its conidia. Trap plants at 0, 0.1, 1 and 4 m from the inoculum source were readily infected under moist conditions. Beyond 9 m from an inoculum source no infection of caraway trap plants was found. Trap plants at 9 m from an inoculum source were infected in one out of three seasons only. Long distance (>9 m) spread could not be demonstrated by the techniques used in this study. The results suggest that, usually, a caraway field is infected by inoculum sources within that field.