1. Plant Disease
  2. Host and Disease Descriptions

Apricot (Prunus armeniaca)-Brown Rot

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Latest revision: 
March 2024
Thin canopy of an apricot tree

Shoot dieback with necrotic leaves and floral tissue.

Photo by Iain MacSwann, 1983.

See:

Cherry (Prunus spp.) - Brown Rot Blossom Blight and Fruit Rot

Cause The fungi Monilinia fructicola and M. laxa can incite a blossom blight, a twig and branch dieback, and a fruit rot of several Prunus spp. including many ornamental and fruit trees. Fungi survive year to year on infected twigs, branches, old flower parts, or mummified fruit. Wind and rain blow spores (conidia and ascospores) to healthy blossoms in spring to begin the infection process during wet weather. Infection does not occur below 50°F and will occur for M. laxa above 55°F. Flowers can be blighted any time floral tissue is exposed but are most susceptible at full bloom. More spores can be produced on this tissue, initiating several more disease cycles during the spring. Under severe conditions, non-flowering shoots or leaves can be infected directly.

Some infections may be symptomless until fruit begins to ripen. The risk of these latent infections is highest from bloom through pit hardening, declines to a low risk at embryo growth then begins to increase as fruit ripen. Ripening fruit are highly susceptible to infection, and more disease cycles can occur near harvest. Fruit that fall to the ground due to lack of pollination, thinning, or overripeness can significantly increase inoculum and the amount of fruit rot at harvest. Fruit infected in the orchard may not show symptoms until it is in storage or transit. High nitrogen fertilization also is associated with increased levels of brown rot.

Both fruiting and ornamental cherries, peaches, nectarines, prunes, plums, almonds, as well as apricots are susceptible. Pome fruit, including quince, can be susceptible under high disease pressure years. The disease is more of a problem west of the Cascade Range.

Symptoms Infected flower parts turn light brown and may develop areas of buff-color (M. fructicola) or gray (M. laxa) spores. Infected petals may look water soaked, which can be mistaken for frost injury. Flowers generally collapse as the fungus invades through the pedicel. Infected flowers often adhere to twigs and spurs through harvest or even winter.

Depending on the fungus and plant infected, the disease may continue into twigs or spurs. Lesions may remain discrete or girdle the twig, causing all distal portions to die. Profuse gumming also may occur in these areas. Again, buff or gray spores (in sporodochia) may develop on these necrotic twigs.

Fruit symptoms begin as small, dark spots that enlarge rapidly. Fruit remains fairly firm and dry relative to a watery rot caused by Rhizopus sp. Production of masses of buff-color spores is equally rapid in the necrotic area.

Cultural control These must be supplemented by chemical methods especially in the wettest areas such as west of the Cascade Range.

  • Remove and destroy infected twigs and branches in summer.
  • Shorten large trees and prune out shaded limbs in summer for a more open canopy that dries out quickly.
  • Remove and destroy all mummified fruit in and around the tree. Cultivating or burying old fruit before the growing season will not reduce the risk of this disease. However, removing fallen fruit (due to thinning or lack of pollination) can significantly reduce the amount of rot at harvest.
  • Control insects that could wound and injure fruit.
  • Avoid wounding fruit during harvest.
  • Cool fruit rapidly after harvest.
  • Use moderate amounts of nitrogen fertilizer.

Chemical control Apply fungicides at redbud, popcorn and full bloom. Apricot sepals and petals are susceptible so the application at red bud is most important. Tank-mix or alternate chemicals from different groups with different modes of action to prevent fungi from developing resistance. Never use sulfur products on apricots.

  • Abound at 12 to 15.5 fl oz/A. May be applied the day of
    harvest. Sprayers used for Abound should not be used on apples. Group 11 fungicide. 4-hr reentry.
  • Bonide Captan 50 WP may be used in home gardens at 1 to 1.5 Tbsp/gal water. H
  • Bravo Weather Stik at 3.1 to 4.1 pints/A. Do not apply after shuck split. Avoid use when honey bees are active due to larval toxicity. Group M5 fungicide. 12-hr reentry.
  • Captan 80 WDG at 1.9 to 3 lb/A. May be applied up to the day of harvest. Not recommended due to concerns about pollinator brood development. Group M4 fungicide.
    24-hr reentry.
  • Cevya at 3 to 5 fl oz/A. May be used day of harvest. Group 3 fungicide. 12-hr reentry.
  • Eagle 20 EW at 2 to 3 fl oz/100 gal water for home orchards
    or landscape use. Can be applied up to the day of harvest. Group 3 fungicide. 24-hr reentry.
  • Echo 720 at 3.1 to 4.1 pints/A, for blossom blight only. Do not apply after shuck split. Avoid use when honey bees are active due to larval toxicity. Group M5 fungicide. 12-hr reentry.
  • Elevate 50 WDG at 1 to 1.5 lb/A. Applications may be made up to and including the day of harvest. Group 17 fungicide. 12-hr reentry.
  • Fixed-copper products are rated with low control. Avoid use when honey bees are active due to bee toxicity. Group M1 fungicides. O
    • Champ WG at 6 to 8 lb/A. Do not apply after full bloom. 48-hr reentry.
    • C-O-C-S WDG at 1 to 2.9 lb/A. 48-hr reentry.
    • Cueva at 0.5 to 1 gal/100 gal water/A. May be used on day of harvest. Group M1 fungicide. 4-hr reentry.
    • Kocide 3000 at 3.5 to 5 lb/A. Do not apply after bloom. 48-hr reentry.
    • Monterey Liqui-Cop at 3 to 4 Tbsp/gal water. Use during bloom only. H
    • Nu-Cop 50 DF at 2 to 3 lb/A. Do not apply after bloom. 48-hr reentry.
  • Fontelis at 14 to 20 fl oz/A. Can be used day of harvest. Group 7 fungicide.12-hr reentry.
  • Indar 2F at 6 fl oz/A plus a wetting agent. Can be used up to the day of harvest. Group 3 fungicide. 12-hr reentry.
  • Inspire Super at 16 to 20 fl oz/A. Do not apply within 2 days of harvest. Group 3 + 9 fungicide. 12-hr reentry.
  • Iprodione-based products. Do not apply after petal fall or more than two (2) times per season. Generally good control if resistance is not a problem. Do not mix with insecticides due to honey bee adult and/or larval toxicity. Group 2 fungicides. 24-hr reentry.
    • Iprodione 4L AG at 1 to 2 pints/A.
    • Meteor at 1 to 2 pints/A.
    • Rovral 4 Flowable at 1 to 2 pints/A.
  • Kenja 400 SC at 12.5 fl oz/A. Do not use within 1 days of harvest. Group 7 fungicide. 12-hr reentry.
  • Luna Experience at 6 to 10 fl oz/A. May be used day of harvest. Group 3 + 7 fungicide. 12-hr reentry.
  • Luna Sensation at 5 to 7.6 fl oz/A. Do not use within 1 day of harvest. Group 7 + 11 fungicide. 12-hr reentry.
  • Merivon at 4 to 6.7 fl oz/A. Do not use with EC or oil-based products. Only nonionic surfactants can be used within 14 days of harvest. May be used day of harvest. Group 7 + 11 fungicide. 12-hr reentry.
  • Miravis at 5.1 fl oz/A. Can be used up to the day of harvest. Group 7 fungicide. 12-hr reentry.
  • Miravis Duo at 13.6 fl oz/A. Can be used up to the day of harvest. Group 3 + 7 fungicide. 12-hr reentry.
  • Ortho MAX Garden Disease Control at 3.75 teaspoons/4gal water. H
  • Pristine at 10.5 to 14.5 oz/A. Can be used day of harvest. Group 7 + 11 fungicide. 12-hr reentry.
  • Problad Verde at 18.1 to 45.7 fl oz/A. Reapply if rain occurs within 12 hours of original application. Do not use within one day of harvest. Group BM01 fungicide. 4-hr reentry.
  • Propiconazole-based fungicides are registered. Limited to two (2) applications. Do not mix with insecticides due to bee toxicity. Group 3 fungicides.
    • Bumper 41.8 EC at 4 fl oz/A. May be used up to and including day of harvest. 12-hr reentry.
    • Infuse Systemic Disease Control at 2 Tbsp/gal water. H
    • PropiMax EC at 4 fl oz/A. Do not use within 10 days of harvest. 12-hr reentry.
    • Tilt at 4 fl oz/A. May be used up to and including day of harvest. 24-hr reentry.
  • Quadris at 12 to 15.5 fl oz/A. May be applied the day of harvest. Sprayers used for Abound should not be used on apples. Group 11 fungicide. 4-hr reentry.
  • Quadris Top at 12 to 14 fl oz/A. May be applied on the day of harvest. Do not mix with insecticides due to bee toxicity. Group 3 + 11 fungicide. 12-hr reentry.
  • Quash at 2.5 to 4 oz/A. Do not use within 14 days of harvest. Group 3 fungicide. 12-hr reentry.
  • QuiltXcel at 14 fl oz/A. May be applied the day of harvest. Sprayers should not be used on apples. Group 3 + 11 fungicide. 12-hr reentry.
  • Rally 40 WSP at 2.5 to 6 oz/A. Can be applied up to the day of harvest. Group 3 fungicide. 24-hr reentry.
  • Rhyme at 7 fl oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-hr reentry.
  • Scala SC at 9 to 18 fl oz/A. Do not within 2 days of harvest. Not for cherry-only for apricot, peach, prune and plum. Group 9 fungicide. 12-hr reentry.
  • Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 0.5 fl oz/gal water. May be applied up to the day of harvest. Do not apply more than seven (7) times per season. Group 3 fungicide. H
  • Tebucon 45 DF at 5 to 8 oz/A. Can be applied up to and including day of harvest. Group 3 fungicide.5-day reentry.
  • Tesaris at 3.5 to 5.6 fl oz/A. Do not use with oil-based products. May be used day of harvest. Group 7 fungicide. 12-hr reentry.
  • Topguard SC at 14 fl oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-hr reentry.
  • Topguard EQ at 6 to 8 fl oz/A. Do not use with silicone surfactants or within 7 days of harvest. Sprayers should not be used on apples. Group 3 + 11 fungicide. 12-hr reentry.
  • Topsin 4.5 FL at 20 to 30 fl oz/A plus another fungicide. Do not use within 1 day of harvest. Group 1 fungicide. 2-day reentry.
  • Vangard WG at 5 oz/A. For blossom blight only. Do not use with X-77. Tank-mix with another fungicide to improve efficacy and to manage resistance. Buffer to a pH of 5 to 7 when tank-mixing with Rovral. Group 9 fungicide. 12-hr reentry.
  • Ziram 76 DF at 6 to 8 lb/A. Do not apply within 30 days of harvest. Avoid use when honey bees are active due to larval toxicity. Group M3 fungicide. 48-hr reentry.

Notes: Do not use sulfur on apricots. Light sulfur injury can cause leaves to cup. Fruit may become brown or have brown spots. Heavy injury may kill buds or buds may only open slightly, leaves can become scorched and withered.

Some registered products offer only suppression of this disease and thus are not recommended for use. These products include Flint Extra.

Biological control

  • Botector (Aureobasidium pullulans strains DSM 14940 and 14941) at 6 to 14 oz/A depending on water volume. Can be applied day of harvest. Compatible with sulfurs, oils, and a few fungicides but not with many synthetic fungicides. 4-hr reentry. O
  • BotryStop (Urocladium oudemansii U3 strain) at 2 to 4 lb/A. Keep refrigerated before use. Compatible with many wetting agents, some fungicides and biologicals but not all. Unknown efficacy in the PNW. 4-hr reentry. O
  • DoubleNickel 55 (Bacillus amyloliquefaciens strain D747) at 0.25 to 3 lb/A. Unknown efficacy. Group BM02 fungicide. 4-hr reentry. O
  • Howler Evo (Pseudomonas chlororaphis strain AFS009) at 1.25 to 7.5 oz /A plus a surfactant. Can be used day of harvest. 4-hr reentry. O
  • Serenade OPTI (Bacillus subtilis strain QST 713) at 14 to 20 oz/A. Active ingredient is a small protein. Use only for blossom blight during bloom. 4-hr reentry. O
  • Serenade Garden Disease Control Concentrate at 2 to 4 fl oz/gal water. Use only for blossom blight during bloom. H O

Reference Mari, M., Casalini, L., Baraldi, E., Bertolini, P., and Pratella, G.C. 2003. Susceptibility of apricot and peach fruit to Monilinia laxa during phenological stages. Postharvest Biology and Technology 30: 105-109.