Fruit and Nut Disease Updates

June 12, 2024

Blueberry Disease Alert: Blueberry Leaf Rust Identified in Mississippi

By: Alan Henn, MSU Extension Plant Pathologist, Department of Agricultural Sciences and Plant Protection, Starkville, MS, and Rebecca Melanson, MSU Extension Plant Pathologist, Central MS Research and Extension Center, Raymond, MS

Blueberry leaf rust has been identified on blueberries in Perry County. Leaf rust is not a common disease of blueberries in Mississippi, but it has been identified occasionally in several Mississippi counties during the last 10 years. Outbreaks tend to be localized but can be severe causing defoliation and reduced yield. Both rabbiteye and southern highbush blueberry varieties differ greatly in their susceptibility to leaf rust. The varieties Bluecrisp, Climax, Delite, Emerald, and Jewel are reported to be highly susceptible, and the varieties Powderblue and Star are reported to be moderately susceptible.

The fungus (Naohidemyces vaccinii) that causes blueberry leaf rust only survives on living plant tissue, so often does not survive winters in Mississippi. Rust fungi have complicated life cycles, producing as many as five types of spores on two different hosts. The alternate host for the blueberry leaf rust fungus are hemlock species (Tsuga spp.), which are not common in Mississippi. An abbreviated life cycle, however, may occur, on primary hosts, including Rhododendron spp. (e.g., orange/Florida azalea, mountain azalea, piedmont azalea, pink azalea, swamp azalea) and Vaccinium spp. (e.g., lowbush blueberry, highbush blueberry, rabbiteye blueberry, thinleaf huckleberry, velvetleaf huckleberry, red huckleberry, lingonberry, and others.

Blueberry growers should scout their fields for symptoms of blueberry leaf rust. Early symptoms on the upper leaf surface begin as yellow (chlorotic) flecks that enlarge to circles. As the chlorotic spots age, the centers turn reddish-brown (Figure 1) and the chlorotic area reduces to a narrow line surrounding the dark center (Figure 2). On the lower leaf surface, the area under the yellow spots will swell into a pustule that will eventually burst. The burst pustule releases visible orangish-brown spores (Figure 3). In late fall and winter, black structures (telia) may be visible.

  

Figure 1. Early symptoms of blueberry leaf rust. Credit: Alan Henn, MSU Extension.

Figure 2. Early symptoms of blueberry leaf rust. Credit: Rebecca A. Melanson, MSU Extension.

Figure 3. Signs of blueberry leaf rust on the underside of a blueberry leaf. Credit: Alan Henn, MSU Extension.

Figure 4. Symptos of blueberry leaf rust. Credit: Alan Henn, MSU Extension.

Overall, infected blueberry leaves may have a light green, chlorotic, or reddish appearance. Edges of leaves in advanced infections may have dead (necrotic) brown edges which may then curl (Figure 4) before dropping to the ground. The canopy density of the plant may seem thin. Defoliation may result in reduced yields the next season.

If blueberry leaf rust is detected, fungicides with efficacy against blueberry leaf rust should be incorporated into a late season and post-harvest fungicide spray program for disease management. Fungicides for blueberry leaf rust are listed in the 2024 Southeast Regional Blueberry Integrated Management Guide as well as the MyIPM Fruit & Nut app; however, a summary of these fungicides is provided below. As always, be sure to completely read and follow the product label. The label is the law. Also, be sure to check state registrations to be sure products are registered for use in Mississippi. Note: For fungicide label purposes, rabbiteye blueberries are a type of highbush blueberry. Any label that allows use on highbush blueberry can be used on rabbiteye blueberries unless specifically prohibited.

Summary of fungicides for blueberry leaf rust: The fungicide chlorothalonil (FRAC M05) is effective but cannot be used prior to harvest. The 2024 Southeast Regional Blueberry Integrated Management Guide lists the most effective fungicides, from excellent to fair, as Proline (a.i. prothioconazole, FRAC 3, excellent); Quilt Xcel (a.i. azoxystrobin + propiconazole, FRAC 11+3, excellent); Quash (a.i. metconazole, FRAC 3, very good); Tilt, Bumper, and PropiMax (a.i. propiconazole, FRAC 3, good); and Pristine (a.i. pyraclostrobin + boscalid, FRAC 11+7, fair). Note: If berries may be exported to EU countries, avoid using any fungicide containing the active ingredient (a.i.) propiconazole.

In southeastern states where the disease has been a problem, fungicides are typically also applied around August to keep plants from defoliating. After warm winters when infected leaves have been retained by the plants, a fungicide application prior to harvest may be warranted.

If the infection is localized, picking and destroying infected leaves (fallen or on the bush) would limit overwintering chances.

 

​April 16, 2020

Staying Connected and Available Resources - Friuts, Nuts, and Vegetables

By: Rebecca A. Melanson, MSU Extension Plant Pathologist, Central MS Research and Extension Center, Raymond, MS

• Building a Mississippi Vegetable, Fruit, and Pecan Producer List. Mississippi State University Extension Specialists are trying to build a list of commercial vegetable, fruit, and pecan producers to help improve our delivery of crop-specific and/or site-specific information to our Mississippi producers. We hope to use this list to email producers about upcoming events and new/updated resources as they become available. Please visit the Producer Registration Webpage (http://msuext.ms/nwslt) for more information about this effort and to add yourself to the list. Let us known what you grow and how you grow it!

• Vegetable Crop Handbook for Commercial Vegetable Production. We were able to get copies of the 2020 Vegetable Crop Handbook printed this year. Those involved in commercial vegetable production in Mississippi can request a FREE hard copy of the book by sending an email request to Janie Ross. Please provide your name, farm name, and complete mailing address. The 2020 Vegetable Crop Handbook is also available online. You can follow the link or visit www.vegcrophandbook.com to download a digital copy of the book. This is a new web address, so if you bookmarked the previous edition of the book, be sure to update your bookmarks. Remember, the focus of the Vegetable Crop Handbook is on commercial vegetable production. Vegetable production information for home gardens is available in The Garden Tabloid.

• Small Fruit Integrated Pest Management Guides for Commercial Production. The integrated pest management guides for small fruits (blueberry, caneberry, muscadine, bunch grape, and strawberry) produced by the Southern Region Small Fruit Consortium have been updated for 2020 and are available on the Southern Region Small Fruit Consortium website (www.smallfruits.org). We are also in the process of printing a limited number of selected guides for distribution to commercial small fruit producers in Mississippi. If you are in need of a hard copy of one of these guides to assist you in your commercial small fruit production, please select the appropriate link to send an email request for a FREE copy of the specific guide: Blueberry IPM Guide (Conventional), Caneberry IPM Guide, Muscadine IPM Guide, Strawberry IPM Guide. Please provide your name, farm name, and complete mailing address. Guides will be mailed out as soon as possible.

• Southern Region Small Fruit Consortium Newsletter. Mississippi State University is now a member of the Southern Region Small Fruit Consortium! We have been working with the Consortium to update various integrated pest management guides for a number of years, but our membership in the Consortium allows greater opportunity for small fruits research and agent training. The Consortium also sends out a quarterly newsletter, Small Fruit News, with articles covering various horticulture and pest management topics. Past issues are available at the Southern Region Small Fruit Consortium website on the News page. There, you can also subscribe to the newsletter to receive it directly in your email inbox!

• Outreach Through Social Media. If you are a social media user, consider “liking” or “following” some of our program pages/accounts to get updates, notices, and information!                                             

On Facebook: MSU Extension Diseases of Vegetables, Fruits, and Pecans (@MSUextDiseasesVFP) by Rebecca Melanson, MSU Extension Plant Pathologist                                              

On Twitter: MSU Extension Plant Diagnostic Lab (@MSUextPlantLab) by Clarissa Balbalian, MSU Extension Plant Diagnostic Lab Diagnostician

• Fruit and Nut and Vegetable Disease Extension Publications. A number of Extension publications on various fruit, nut, and vegetable diseases are available on the Fruit and Nut Disease Publications and Vegetable Disease Publications pages on the MSU Extension website. New publications are added when they become available, and new and updated publications are marked as such on these pages. A new publication recently added to this page is the publication “Bacterial Speck and Bacterial Spot in Tomatoes”. A number of other publications are in the process of being produced or updated, and I hope these will be available in the near future. Follow MSU Extension Diseases of Vegetables, Fruits, and Pecans on Facebook and register to be on our producer list to receive updates!

• MSU Extension Plant Diagnostic Lab Services. The MSU Extension Plant Diagnostic Lab will continue to operate during the Safer at Home order. If you are in need of plant disease diagnostic assistance or nematode services, please visit the MSU Extension Plant Diagnostic Lab website (https://extension.msstate.edu/lab) for information on how to submit samples. Walk-in clients are prohibited from entering the lab but may leave samples on the cart located outside the door. Digital images may also be sent by email to Clarissa Balbalian. Please contact the Diagnostic Lab if you have questions regarding sample submission and diagnosis. (Updated May 7, 2020)

 

May 29, 2018

Do Your Homework When Using Regional Pest Management Guides

By: Rebecca A. Melanson, MSU Extension Plant Pathologist, Central MS Research and Extension Center, Raymond, MS

     Regional pest management guides, such as the Southeastern U.S. Vegetable Crop Handbook and the Southeastern Peach, Nectarine and Plum Pest Management and Culture Guide, are excellent resources for commercial growers. These guides list products available for use against various diseases, insects, and weeds and often provide efficacy information for those products against specific pests.

     However, every product listed in these regional guides may not be registered for use in Mississippi. Before purchasing and applying a product, be sure that the product is registered for use in Mississippi. State registration information can be obtained from a number of online databases. Please see the MSU Extension publication Pesticide Label Databases for a list of databases that provide state registration information. And remember, the label is the law. Be sure to read and follow all label directions.

 

Clearing Up the Confusion: Plant Diagnostic Lab vs. Soil Testing Lab

By: Clarissa Balbalian, Diagnostician and Lab Manager, MSU Extension Plant Diagnostic Lab, Starkville, MS

     As sample submission season gears up, it is important to review the difference between services provided by the MSU Extension Plant Diagnostic Lab and the MSU Extension Soil Testing Lab as well as which forms should accompany samples submitted to these labs.  The Plant Diagnostic Lab analyzes soil for plant parasitic nematodes and plant tissue for disease.  The Soil Testing Lab analyzes soil for nutrients, pH, and soluble salts and plant tissue for nutrients.  The two labs handle samples in vastly different ways.  Please make every effort to submit your samples to the proper lab with the proper paperwork. This will help ensure the sample will be handled appropriately and will not accidentally be damaged to the point that it cannot be used for its intended purpose.

     The tables below outline the services provided by each lab and the form that should be used to accompany samples submitted to those labs. 

 

Plant Diagnostic Lab

190 Bost North, Rm. 09

Box 9612

Mississippi State, MS 39762

662-325-2146

Website: http://extension.msstate.edu/lab

Lab Director: Clarissa Balbalian

 

Service	Form*
Plant Disease Analysis	Plant Disease Sample Submission Form (F1139) (PDF)
Nematode Testing	Nematode Sample Submission Form (F448) (PDF)

*Forms are also available on the Plant Diagnostic Lab website.

 

Soil Testing Lab

190 Bost North, Rm. 01

Box 9610

Mississippi State, MS 39762

662-325-3313

Website: http://extension.msstate.edu/lawn-and-garden/soil-testing

Lab Director: Dr. Keri Jones

 

Service	Form*
Plant Tissue Analysis (nutrients)	Plant Analysis Form TTT
Soil Testing (nutrients, pH, soluble salts)	Soil Testing Laboratory AAA

*Forms are available from the Soil Testing Lab or your local county Extension office.

 

January 26, 2018

Sample Collection and Assistance for Disease Identification

By: Rebecca A. Melanson, MSU Extension Plant Pathologist, Central MS Research and Extension Center, Raymond, MS

     Diagnosis is the first step in disease management. It is important to know what disease and pathogen is affecting a plant or crop so that appropriate disease management actions can be taken. When seeking assistance from county agents or specialists, it is important to provide relevant information that can help your local county agent or specialist to identify the problem in a timely manner and determine the best management options. It is always a good idea to provide at least the following information: the affected plant host and variety, the extent of the damage, a description of the symptoms, and your preferences for disease management, which may range from conventional to strictly organic. Additional information such as disease history and recent pesticide use is also valuable.

     Often times, digital images (photos) of plants are also received from growers or homeowners wanting to know what is wrong with their plant. These images can be very valuable and provide additional information regarding a situation, but it is often not possible to diagnose a disease problem from a digital image. Information about the types of images that are most useful and examples of good images are available in MSU Extension publication P3022 Taking Photos of Plant Disease Problems. If sending photos to your local county agent or specialist, please remember to make sure that your photos are in focus and that you also provide the information requested above.

     Despite the valuable information that can be provided through words and images, it is often still necessary to examine a physical sample for diagnosis. Samples submitted for diagnosis should not be in an advanced stage of decay. They should also be fresh and arrive undamaged. Instructions for collecting and packaging samples for diagnosis are available in MSU Exteension publication M1562 How to Collect and Package Plant Disease Specimens for Diagnosis.

(The majority of this article originally appeared in the April 2017 issue of the North MS Fruit and Vegetable Newsletter.)