At-harvest prediction of grey mould risk in pear fruit in long-term cold storage

The objective of this research was to develop a model to predict, at-harvest, the risk of grey mould in pear fruit (Pyrus communis) in long-term cold storage based on multiple variables including: i) density of Botrytis cinerea DNA on fruit surfaces at harvest; ii) fungicide application within 4 weeks before harvest; iii) rainfall within 2 weeks before harvest; and iv) a relative orchard tree-growth and management rating. The model classified grey mould risk as low, moderate, high, or extreme. Data were collected for 2 years in six pear orchards in New Zealand and for 3 years in eight pear orchards in the Mid-Columbia district of Oregon and Washington, USA. Risk predictions varied from low to extreme, and the corresponding grey mould incidence varied from 0.1 to 14.0%. The multiple R-square was 0.973 when all predictors were included. The Spearman rank correlation coefficient (r_s) relating the predicted grey mould risk level to the actual incidence of grey mould in pear fruit was 0.882 (P = 0.000). The decay risk prediction model presented herein appears robust and gave reliable predictions of grey mould risk in d'Anjou and Bosc pear fruit from Oregon-Washington and New Zealand in all three years.