Survey of the incidence of chestnut rot in south-eastern Australia

Chestnut rot of Castanea sativa (European chestnut) and C. crenata (Japanese chestnut) x C. sativa hybrids is a significant problem facing the Australian chestnut industry. It affects the chestnut kernel, symptoms occur as pale, medium and dark brown lesions occurring on the endosperm and embryo. Twenty-two orchards in Victoria and New South Wales were surveyed in 2008, and 21 of these were again surveyed in 2009. All 22 orchards were affected by chestnut rot. Incidence at individual orchards up to 72 % was found in 2008, and 35 % in 2009. Incidence varied widely between orchards and within individual orchards between the 2 years. All varieties were affected, including Decoppi Marone, Purton's Pride and Red Spanish, displaying examples of both high incidence (> 1 %) and industry acceptable incidence (0-1 %) depending on orchard and year. In 2008 and 2009, surveys of Sydney Markets showed incidence of > 1 % (2008: varieties Decoppi Marone, Purton's Pride; and in 2009: varieties Purton's Pride, Red Spanish). The early December flowering Red Spanish had significantly higher average incidence than the early to mid December flowering Decoppi Marone and Purton's Pride, suggesting that the timing of flowering may be an important factor affecting incidence. There was a mild positive correlation between orchard incidence and December rainfall of the previous year (r(2) = 0.4), indicating rainfall during the chestnut flowering period had a mild effect on incidence.