Brown rot, bunch rot and grey mould
Cherry brown rot
Cherry brown rot is caused by the fungi Botrytis cinerea and Monilinia spp. The fungi can enter the fruit during flowering, or through injuries later in the season. Infected fruit can become rotten and covered in a mass of light grey-brown spores. If it is left on a tree, or in the orchard, the mummified fruit will carry spores over the winter and become the source of blossom infection in the next season.
Brown rot is spread by wind, rain splash and insects. Dew can provide enough moisture to allow infection of ripe fruit. The two most susceptible periods for fruit infection are flowering and just before harvest.
Nearly all growers use fungicidal sprays during flowering.
Bees can deliver biological control to flowers.
Strawberry grey mould
Strawberry grey mould is another fungal disease caused by Botrytis cinerea.
In strawberries flowering and picking occurs simultaneously.
Therefore growers are restricted in the frequency and products they can spray.
A biological control agent for strawberry grey mould will probably become available in 2016. Bees can deliver this safely, only to the flowers where it is needed. The use of biological control greatly reduces the chances of the evolution of resistence.
Botrytis bunch rot in grapes
The same fungus that causes brown rot in cherries, Botrytis cinerea, causes bunch rot in grapes. During latent infection, spores of the fungus enter the flower and lay dormant until the grapes ripen.
This is known as a latent infection.
After ripening, moist conditions are conducive to the development of Botrytis bunch rot. Late infection can occur when the berries have been injured by insect, bird or hail damage close to harvest.
Grape flowers are sprayed during flowering to prevent latent infection. The fungus Botrytis cinerea is increasingly becoming resistant to fungicides.
There are very few alternatives for the management of Botrytis close to harvest due to residue concerns and fungicide resistance problems.
