Spore dispersal, diurnal pattern and viability of Monilinia spp. conidia and the relationship with weather components in an organic apple orchard

Monilinia spp is the causative genus of fruit rot in fruit crops in the temperate regions of the world (Byrde & Willetts, 1977; Holb, 2006, 2008a). Dispersal of Monilinia spp. conidia can occur mainly by wind, water, insects, birds and man. Short range transport of conidia could be considered by splash dispersal (Byrde & Willetts, 1977). Few studies monitored dispersal of M. fructigena conidia. Airborne conidia have been trapped on exposed dishes and vaseline slides (Horne, 1933). Water was shown to be an important factor for spreading conidia within the tree (Pauvert et al., 1969). Insect dispersal of conidia has also been an importamt factor from one fruit to another (Croxall et al., 1951; Lack, 1989). Studies demonstrated a low aerial concentration of M. fructigena in integrated apple orchards (Van Leeuwen et al., 2000; Xu et al., 2001; Holb, 2008b) while in organic apple orchards high conidial concentration were recorded (Holb, 2008b; Holb et al., 2011). Previous studies showed that viability of trapped conidia was 60 % (Holb, 2008b). Relative humidity, mean temperature, and wind were shown to be important in explaining the variation in hourly spore counts of M. fructigena conidia (Holb, 2008b; Bannon et al., 2009). The aims of this two-year study were to i) monitor conidial content of Monilinia spp. in the air from mid-May until harvest; ii) determine diurnal periodicity of trapped conidia iii) evaluate viability of trapped spores; and iv) correlate spore data with weather variables of relative hunidamidity, temperature and rainfall in an organic apple orchard. Materials and methods