Quiescent fruit infections of peach, apricot, and plum in New Zealand caused by the brown rot fungus Sclerotinia fructicola

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Abstract
Studies showed that a quiescent infection of stone fruits by the brown rot pathogen, Sclerotinia fructicola, previously reported in Australia, also occurred in New Zealand on peach, apricot, and plum fruits. The infections occurred in small, superficial, halo-shaped blemishes, quite distinct from other fungal infections. Quiescent infections of developing fruits occurred during prolonged warm, wet periods between late bloom (September) and January, and were first observed in late October-early November. Sources of inoculum were the current season's blighted blossoms or fruit “mummies” in the tree, and transport of inoculum was by rain splashing. Degree of quiescent fruit infection in trees was closely linked to that of blossom blight, being reduced when blossom blight was controlled with fungicides. Reactivation of quiescent infections occurred during warm, wet periods, resulting in decay of green or ripe fruit. When quiescent infection was severe a green fruit “cover” spray programme was necessary to prevent harvest losses. Although eradication of some infections resulted, sufficient still remained viable to cause heavy losses in storage. In fungicide dip tests of peaches and apricots, triforine inhibited reactivation of quiescent infections more effectively than benomyl. So far only field recording of the condition has been made on plum fruits.

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