BROWN ROT
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Beginner
This pest affects:
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Scientific Name
Monilinia fructicola
Identification
Blossom Blight
- Infected blossoms wilt, shrivel and become covered with greyish mold
- Petals may appear light brown or water-soaked
Twig Blight and Canker
- The infection may spread from infected blossoms to twigs, causing brownish, oval cankers that may girdle and kill twigs
- Gumming may also occur on infected twigs
Fruit Rot
- First appears as small, circular brown spots that increase rapidly in size causing the entire fruit to rot
- Greyish-tan spores appear in tufts, often in concentric rings on rotted areas
- Fruit that appear healthy at harvest may develop rot post-harvest
- Infected fruit eventually turn into shriveled, wrinkled black mummies that may drop or remain attached to the tree through the winter
Often Confused With
Rhizopus fruit rot – fruit rot – dense white mycelium with black spores; soft watery rot
Frost injury- blossom blight – follows low temperatures; no cankers associated with injury
Paraquat injury – fruit rot -
Period of Activity
Trace bloom through shuck fall for blossom blight.
Peak fruit infection periods are from shuck split through pit hardening/June drop and again as fruit change colour.
Brown rot can be serious on injured fruit such as cherries split by rain or when fruit are clustered together and in contact with each other.
Scouting Notes
History of incidence in each block, cultivar susceptibility, and surrounding pressure (other peach blocks and fruit crops such as cherries, plums, apricots etc infected in the past) are all-important factors.
Blossom blight observations during bloom and shuck may help assess the effectiveness of pest sprays and the need for follow-up controls.
Monitor approximately every three to five days during the preharvest period. Brown rot will show up first in areas near sources of inoculum (such as earlier maturing varieties) and where fruit may be physically injured. An estimate of the potential for postharvest rot to develop can be determined by harvesting 10 mature, healthy fruit from each sample tree. Wound each of these fruits several times by stabbing them with a knife [1/4 inch (6-7 mm) deep] and holding them in a closed plastic bag at room temperature for 24 to 48 hours. Record the percent rotted fruit.
Threshold
There is no threshold for initiating blossom blight or brown rot control. Fungicides should be applied before infection occurs.
Advanced
This pest affects:
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Scientific Name
Monilinia fructicola
Identification
Blossom Blight
- Infected blossoms wilt, shrivel and become covered with greyish mold
- Petals may appear light brown or water-soaked
Twig Blight and Canker
- The infection may spread from infected blossoms to twigs, causing brownish, oval cankers that may girdle and kill twigs
- Gumming may also occur on infected twigs
Fruit Rot
- First appears as small, circular brown spots that increase rapidly in size causing the entire fruit to rot
- Greyish-tan spores appear in tufts, often in concentric rings on rotted areas
- Fruit that appear healthy at harvest may develop rot post-harvest
- Infected fruit eventually turn into shriveled, wrinkled black mummies that may drop or remain attached to the tree through the winter
Often Confused With
Rhizopus fruit rot – fruit rot – dense white mycelium with black spores; soft watery rot
Frost injury- blossom blight – follows low temperatures; no cankers associated with injury
Paraquat injury – fruit rot -
Biology
The same strain of Monilinia infects all stone fruits. The fungus overwinters in mummified infected fruit on the ground or in the tree, and in twig cankers. Two types of spores are produced in spring which can infect blossoms. Conidia are produced on cankers and fruit mummies in the tree. Apothecia (small funnel-shaped structures) form on mummies lying on the ground. The apothecia discharge ascospores during the bloom period, but do not contribute to fruit infection later in season. Apothecia are seldom found in the orchard and fruit mummies hanging in the tree are thought to be the main source of initial inoculum since apothecia are rare in Ontario.
Conidia are disseminated by wind and rain and germinate rapidly under favourable conditions. Optimum temperatures for blossom and fruit infection range from 20 to 25ºC.
Blossoms cannot be infected until petals are open. Blossom blight can be severe enough to reduce the crop; however, early sporulation on even a few infected blossoms provides more inoculum for later fruit infections. Conidia may be produced on infected blossoms and shoots throughout the remainder of the growing season, although sporulation from infected blossoms tends to decline over the summer when early-infected fruit become the major source of conidia. These conidia may infect injured green fruits; nonabscised, aborted fruits; green fruits thinned after the pit hardening stage and dropped under the trees; and ripening fruits as they mature. Non-abscised, aborted fruit in trees and thinned fruit on the orchard floor are important sources of secondary inoculum for fruit brown rot.
Under optimum temperature conditions, fruit infections can occur with as little as three hours of wetness when inoculum levels are high. Longer wet periods (greater than 12 hours) during infection cause symptoms to develop more rapidly. Susceptibility to latent infections is moderate at bloom stage, increases to reach its highest level at about pit hardening, and subsequently decreases, reaching the lowest level in early June at embryo growth. Fruit susceptibility, increases again along with fruit development and maturity until harvest. In most orchard situations, inoculum produced on early maturing cultivars causes a continuing outbreak that affects late maturing cultivars.
Fruit infection may occur by direct penetration of the germinating spore through the cuticle; however, wounded fruit are infected much more readily than nonwounded fruit. Physical injuries provide entry points for brown rot. Plum curculio, tarnished plant bug, stink bugs, oriental fruit moth and other insects commonly produce entry wounds. Conidia can also enter through hail wounds, limb rubs, twig punctures, and fruit cracks–as well as a variety of picking and packing injuries. Widespread wounding is the chief cause of the rapid buildup of brown rot as the fruit begin to mature. At harvest, apparently healthy fruit usually are contaminated with spores which, under favorable conditions, may later decay during storage and marketing.
Period of Activity
Trace bloom through shuck fall for blossom blight.
Peak fruit infection periods are from shuck split through pit hardening/June drop and again as fruit change colour.
Brown rot can be serious on injured fruit such as cherries split by rain or when fruit are clustered together and in contact with each other.
Scouting Notes
History of incidence in each block, cultivar susceptibility, and surrounding pressure (other peach blocks and fruit crops such as cherries, plums, apricots etc infected in the past) are all-important factors.
Blossom blight observations during bloom and shuck may help assess the effectiveness of pest sprays and the need for follow-up controls.
Monitor approximately every three to five days during the preharvest period. Brown rot will show up first in areas near sources of inoculum (such as earlier maturing varieties) and where fruit may be physically injured. An estimate of the potential for postharvest rot to develop can be determined by harvesting 10 mature, healthy fruit from each sample tree. Wound each of these fruits several times by stabbing them with a knife [1/4 inch (6-7 mm) deep] and holding them in a closed plastic bag at room temperature for 24 to 48 hours. Record the percent rotted fruit.
Threshold
There is no threshold for initiating blossom blight or brown rot control. Fungicides should be applied before infection occurs.
Management Notes
Remove mummified fruit from trees before bloom.
Prune out any cankered or dead twigs as they are found.
Prune to avoid excessive overcrowding of branches and clustering of fruit to increase air circulation, promote rapid drying, and increase light and spray penetration.
Fertilize to maintain optimum nitrogen/potassium balance.
Removing rotten fruit from the tree will reduce initial inoculum. Removing fallen fruit from the ground is less practical, but may be an option in small blocks or for organic growers.
Minimize fruit injury by insects and birds.
Pick and handle fruit carefully to avoid injuring or bruising fruit at harvest. Pick only sound fruit. Discard fruit with brown spots or rot. Dispose of culls and rotted fruit promptly by burying. Pre-cool and keep fruit in cold storage until it reaches destination. Use clean containers and keep packing areas clean.
Avoid dumping rotten fruit in one location, which could become the starting point for disease and insect outbreaks the following season.
No cultivar of any stone fruit is immune to brown rot Japanese plum cultivars appear to be less susceptible than European (blue) cultivars Sweet cherries are more susceptible to brown rot than sour cherries. Some cherry varieties such as Lapins tend to produce large clusters of fruit. Brown rot may develop in these clusters more easily due to difficulty of obtaining good fungicide coverage and slower drying of fruit in the middle of the clusters.
Management with fungicides – Fungicides are used to control brown rot in commercial orchards. While blossom infection does not occur until petals open, some locally systemic fungicides applied to petals will translocate into the susceptible flower parts See OMAFRA Publication 360, Fruit Crop Protection Guide.
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Chapter 5 - Peach Calendar: Recommendations for pink, bloom, petal fall, shuck split to shuck fall, second generation OFM, third generation OFM, pre-pick. |
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Chapter 5 - Apricot Calendar: Recommendations for bloom, petal fall, shuck split, shuck fall, first cover, pre-pick to harvest. |
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Chapter 5 - Plum Calendar: Recommendations for popcorn, bloom, petal fall, shuck fall, first cover, second cover, pre-pick. |
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Chapter 5 - Sweet Cherry Calendar: Recommendations for white bud, bloom, shuck split, first cover, second cover, third cover, pre-pick. |
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Chapter 5 - Sour Cherry Calendar: Recommendations for bloom, petal fall, shuck split, third cover, pre-pick. |
