
%0 Journal Article
%A Villalta, O. N. 
%A Washington, W. S. 
%A Rimmington, G. M. 
%A MacHardy, W. E. 
%T Environmental factors influencing maturation and release of ascospores of <emph type="2">Venturia pirina</emph> in Victoria, Australia
%J Australian Journal of Agricultural Research
%D 2001/07/25
%V 52
%N 8
%P 825-837
%K pear scab, ascospore maturity, epidemiology,Pyrus communis.
%R https://doi.org/10.1071/AR00093
%U https://www.publish.csiro.au/paper/AR00093 
%X The influence of moisture, light, and temperature on Venturia pirina ascospore maturation and discharge was studied during 1992&#8211;99 in 2 pear-growing regions in Victoria. In each year and site, mature ascospores were trapped over a 3-month period beginning a few days before or at the green-tip stage of pear tree development in early September and ending in late November, with the majority of ascospores ((&#62;80%) trapped between green-tip and petal-fall. Ascospore discharge was associated with rain and dew, with 90&#8211;98% of the season&#8217;s total number of ascospores trapped during rain events and 2&#8211;10% trapped during dew events in the 12 data sets examined. Most ascospores were trapped (82.5&#8211; 99.9%) during daytime (0600&#8211;1800 hours). The 0.1&#8211;17.5% of ascospores detected during night time (1900&#8211;0500 hours) were trapped mainly within 1&#8211;3 h of dawn or dusk. There were linear relationships between the logit of cumulative percentage of ascospore maturation and temperature accumulation (above 0 degree-days), calculated both daily and for days with >= 0.2 mm of rainfall. Six linear regression equations were formulated with 10 years of field data and using the 2 methods of accumulating degree-days, to predict the cumulative percentage of matured ascospores. Predictions were compared with additional field and laboratory observations not used in the formulation of the linear equations. The importance of the temperature-based linear equations is discussed in relation to the prediction of pear scab ascospore maturity for use in a pear scab management program. 
