Scala® Brand SC Fungicide and Luna® Brand Fungicides for Management of Brown Rot Blossom Blight in Almonds at Pink Bud
January 28, 2025
What are the characteristics and symptoms of brown rot blossom blight (BRBB) caused by the fungi Monilinia laxa and M. fructicola?
The fungal disease survives as cankers on twigs, diseased flower parts, and spurs. Overwintering spores are spread by wind and splashing rain. A wet environment (rain, dew, fog) favors infection with temperature determining how quickly blossom infection occurs. At 50 °F, 18 hours of leaf wetness (LW) are required for blossom infection to occur, but at 68 °F only 8 hours of LW are required. During dry years, high humidity can favor BRBB development. Brown rot blossom blight symptoms include the collapse of spurs and leaves, and the base of infected flowers may secrete a gummy substance. Twig cankers have tan centers with dark margins. Under high humidity, gray to tan spore masses form on flower parts and twig cankers.1
What is the disease triangle and why is it important for the development of BRBB?
For the development of any crop disease, three factors are necessary: a pathogen must be present, as must a susceptible host, and growing conditions must be favorable for the pathogen to exist and reproduce. In the case of BRBB, the pathogen is most often the fungus Monilinia laxa, though occasionally BRBB can be caused by M. fructicola. A susceptible host is an almond tree that is not genetically resistant to the fungus. A favorable environment is the presence of rain, fog, or dew with temperatures between 64 to 77 °F.2
How can susceptible almond trees be protected from BRBB infection?
Integrated Pest Management (IPM) techniques are important for reducing the potential for infection. If possible, almond trees with low susceptibility should be considered for newly planted orchards. Otherwise, growers should be mindful that the pathogen is present in a growing area and infection could occur if disease triangle factors are met. To address potential infections, a labeled, preventative fungicide that is properly and timely applied can help reduce the potential for fungal spores to start growing after landing on a susceptible pink bud. If symptoms are observed during routine scouting, a labeled, curative, and preventive fungicide should be considered to kill the existing fungus and prevent the potential for future fungal growth.
What are the recommended Bayer Crop Science fungicides for managing BRBB?
Scala® brand SC Fungicide, Luna Sensation® Fungicide, and Luna Experience® Fungicide offer protection properties for BRBB.3,4,5 Labels for each product MUST be read thoroughly prior to any application.
What is Scala® brand SC Fungicide?
Scala® brand SC Fungicide is a sprayable, systemic, foliar fungicide with the active ingredient pyrimethanil (Group 9) labeled for the control of BRBB.3 The fungicide has curative and preventive activity. Its systemic characteristic allows for rapid penetration and redistribution inside the bud and blossom (Figure 1).
Besides BRBB, is Scala® brand SC Fungicide labeled for the control or suppression of other almond diseases?
Scala® brand SC Fungicide is also labeled for the control of green fruit rot or jacket rot (Botrytis cinerea), shot hole (Wisonomyces carpophilus), and Botryosphaeria blight (Botryosphaeria dothidia). It is labeled for the suppression of scab (Cladosporium spp.).3
When and at what rate should Scala® brand SC Fungicide be applied to help control BRBB?
For optimum results, begin applications as soon as almonds and growing conditions become favorable for BRBB infection. Almonds become susceptible at the appearance of pink buds (5 to 10% bloom) to full bloom. When used alone, use labeled rates of 9 to 18 fl oz/acre.3 University of California information indicates full bloom is the most effective time for treatment.1
What is Luna Sensation® Fungicide?
Luna Sensation® Fungicide is a broad spectrum, systemic, foliar fungicide with two modes of action labeled for the control of BRBB. The fungicide contains the active ingredients fluopyram (Group 7) and trifloxystrobin (Group 11).4 Its systemic characteristic allows for penetration into buds, blooms, and new tissue.
Besides BRBB, is Luna Sensation® Fungicide labeled for the control or suppression of other almond diseases?
Luna Sensation® Fungicide is also labeled for the control of shot hole (Wisonomyces carpophilus), anthracnose (Colletotrichum acutatum), Alternaria (Alternaria alternata), scab (Cladosporium carpophilum), rust (Tranzschelia discolor), green fruit rot or jacket rot (Botrytis cinerea), and powdery mildew (Sphaeotheca pannosa and Podosphaera tridactyla). It is labeled for the suppression of hull rot (Rizopus spp. and Monilinia spp.)4
When and at what rate should Luna Sensation® Fungicide be applied to help control BRBB?
The recommended application time is full bloom through petal fall, and it cannot be used past two weeks post petal fall (Figure 2). Per the label, applications should be applied at the critical timings for disease control.4 Applications should be continued as needed on a 7- to 14-day interval. Labeled rates are 5.0 to 7.6 fl oz/acre. When disease pressure is severe, use the higher rates and/or shorter intervals.4
What is Luna Experience® Fungicide?
Luna Experience® Fungicide is a broad spectrum, systemic, foliar fungicide with two modes of action labeled for the control of BRBB. The fungicide contains the active ingredients fluopyram (Group 7) and tebuconazole (Group 3).5 Its systemic characteristic allows for penetration into buds, blooms, and new tissue.
Besides BRBB, is Luna Experience® Fungicide labeled for the control or suppression of other almond diseases?
Luna Experience® Fungicide is also labeled for the control of shot hole (Wisonomyces carpophilus), anthracnose (Colletotrichum acutatum)*, Alternaria leaf spot (Alternaria alternata)*, scab (Cladosporium carpophilum)*, rust (Tranzschelia discolor)*, green fruit rot (Botrytis cinerea), jacket rot*, and powdery mildew (Sphaeotheca pannosa and Podosphaera tridactyla).5
*Not for use in California without a supplemental label.
When and at what rate should Luna Experience® Fungicide be applied to help control BRBB?
The recommended application time is two weeks post petal fall, and it cannot be used past two weeks post petal fall. Per the label, applications should be applied at the critical timings for disease control.5 Applications should be continued as needed on a 7- to 14-day interval. Labeled rates are 6.0 to 17.0 fl oz/acre. When disease pressure is severe, use the higher rates and/or shorter intervals.5
Should fungicide resistance be considered?
Yes, continuous use of fungicides with the same mode of action (MOA) can potentially cause pathogens to develop resistance to that MOA. Rotating among the different, available MOA fungicidal products should be practiced. Rotating with Scala® brand SC Fungicide (one MOA, Group 9), Luna Sensation® Fungicide (two MOAs, Groups 7 and 11), and Luna Experience® Fungicide (two MOAs, Groups 7 and 3) can help reduce the potential for resistance development.1
Sources
1Adaskaveg, J.E., Gubler, W.D., Duncan, R.A., Stapleton, J.J., Holtz, B.A., and Trouillas, F.P. 2017. Brown rot blossom blight. Agriculture: Almond Pest Management Guidelines. Publication 3431. https://ipm.ucanr.edu/agriculture/almond/brown-rot-blossom-blight/#gsc.tab=0
2Johnson, J.R. 2020. Almond flower, foliar, and fruit diseases and their management. West Coast Nut. https://wcngg.com/2020/04/07/almond-flower-foliar-and-fruit-diseases-and-their-management/
3Scala® brand SC Fungicide label. Bayer Crop Science
4Luna Sensation® Fungicide label. Bayer Crop Science.
5Luna Experience® Fungicide label. Bayer Crop Science.
Web sources verified 11/22/24. 7311_479125
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Always read and follow pesticide label directions, insect resistance management requirements (where applicable), and grain marketing and all other stewardship practices.
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