Ministry of Agriculture
Botrytis Rots of Pome and Stone Fruit
Botrytis cinerea is a common fungus that can cause fruit rot problems in the field and post-harvest in both stone and pome fruits. It is considered to be a minor problem in the field, but can contribute to post-harvest losses in the packinghouse.
Green Fruit Rot
Botrytis can cause green fruit rot of immature cherries. Symptoms include blossom blight and smooth brown lesions on cherry fruit. The disease is favoured by wet weather during the blossom period. It has occurred in the Okanagan, but is not common.
Botrytis rot on cherry at the immature green fruit stage.
Botrytis Rot of Mature Cherry Fruit
Botrytis rot on mature cherry fruit occurs in the Okanagan, and can be mistaken for brown rot. Fruit develops a brown decay and becomes covered with a growth of light brown or grey spores. Infected fruit becomes soft and watery. Botrytis tends to be worse on varieties which develop tight clusters of fruit. Botrytis will grow on aborted fruit and trapped leaf debris within the clusters, which then spreads to adjacent fruit. Fungicide coverage within tight clusters can also be difficult.
|Early and advanced symptoms of Botrytis rot on 'Lapins' cherry|
|Botrytis rot developing in a cluster of 'Rainier' cherry. Note trapped leaf debris.|
Botrytis and brown rot look very similar on infected cherry fruit. Brown rot tends to sporulate in a more tufted pattern. Laboratory examination may be required to distinguish between brown rot and Botrytis. They are easily distinguished under the microscope.
|Botrytis on cherry fruit||Brown rot on cherry fruit|
Dry Eye Rot in Apple
Botrytis cinerea can cause a disease in apple known as dry eye rot or blossom end rot. This is not common, but has occurred in the Okanagan in wet years, with infection occurring during the blossom period. Initial symptoms include a reddish discoloration at the calyx end. A soft, water soaked lesion forms which expands to several millimetres and dries out forming a sunken brown lesion. Fruit may drop prematurely. If infected fruit are harvested, they will have a greatly increased incidence of botrytis rot in storage.
|Dry eye rot symptoms on 'MacIntosh' apple, caused by Botrytis cinerea||Dry eye rot symptoms on 'MacIntosh' and 'Ambrosia' apple, caused by Botrytis cinerea|
Post-harvest Botrytis Rot
Botrytis is an important cause of post-harvest losses in the packinghouse for both stone and pome fruit. It can develop at cold temperatures, and has the ability to spread in storage.
On pome fruit, Botrytis causes a soft, spongy rot with a sweet, cider-like odour. As the rot progresses, the fungus produces masses of gray spores on the surface of affected fruits. The infection may spread from fruit to fruit during storage, producing "nests" or "pockets" of decayed fruit. Small black resting bodies (sclerotia) may eventually form on infected fruit.
Fontelis (penthiopyrad) is registered to control botrytis rot on stone fruit. Many fungicides used for brown rot, such as Rovral, Pristine, Cantus, Elevate, Vangard, Bravo and captan, also have good activity against Botrytis. (Note - Vangard is not registered on cherries; Elevate and Bravo are not registered on apricots or plums). Optimal spray timing is not well understood, but should include protective coverage from full bloom through shuck fall, which are the highest risk stages for infection. Additional sprays may be needed to protect ripening fruit where disease pressure is high. On cherry varieties that cluster heavily, ensure good spray coverage into the clusters before they close up.
On cherries, when pruning remove excessive branches to allow for increased air flow and shorten current season’s growth to reduce fruit cluster formation.
On apple, thin out fruit showing symptoms of dry eye rot. Infected fruit will not hold up well in storage.
Scala (pyrimethanil) is registered for use in the orchard to help control post-harvest rots of apple in the packinghouse. Apply 14 days before harvest to help control storage rots caused by Botrytis and Penicillium.
There are no fungicides currently registered specifically for Botrytis on apples at the blossom stage. Fungicides used for apple scab at the bloom to petal fall stage may help to reduce the incidence of dry eye rot and other post-harvest rots that originate in the orchard.
Post-harvest decay in the packinghouse may be managed using a post-harvest fungicide treatments and good sanitation practices. Currently Mertect (thiabendazole) and Scholar (fludioxonil) are registered for post-harvest application to apple and pear fruit in Canada.
Updated January 2013