In this section:
Brown Rot
Cause
Fungus Monilinia fructicola
Affected
Mainly peaches, nectarines and apricots, but other stone fruit can be affected.
Symptoms
Infected blossoms turn brown and die, remaining attached to the twigs for most of the season. The fungus continues to develop on the dead tissue and spreads to other parts of the tree. Infected twigs may ooze gum near areas of dead or dying bark.
The most recognisable symptom of brown rot is on the maturing fruit. It first appears as a small brown spot that quickly enlarges (3-5mm/day on ripe fruit) to a large firm brown patch. Within three to five days the whole fruit may be rotted and soon become covered with a light grey-brown mass of spores. If the fruit is left on the tree it will shrivel and dry out. This mummified fruit either on the tree or on the ground acts as a source of infection for the following season.
Conditions favouring
The brown rot fungus infects blossoms, twigs and fruit after periods of warm, wet weather in spring and summer. Thunderstorms often provide ideal infection conditions.
Flowering is the period most critical for infection. If cover sprays are not applied during this period and a few days of warm humid or wet weather occur, brown rot can quickly cause severe damage to flowers and young fruitlets.
Control
The removal of all mummified fruit and diseased wood at pruning is essential to reduce the amount of carryover inoculum present for the next season. This diseased material should be burnt or buried, because if left on the ground, it remains able to produce many spores which act as a source of infection next season.
Trees should be pruned to prevent overcrowding of branches. This improves the air circulation and is particularly important in the moister areas of production, ie the Barossa Valley. It also allows better spray penetration and coverage.
Spray coverage at early and mid flowering is important for control. If brown rot has been a problem in the past it is suggested that systemic fungicides are used at these times to maximise control.
