Tag: botrytis

Strategies for Effective Management of Botrytis and Anthracnose Fruit Rot in Strawberries

Emily Zobel on

Strategies for Effective Management of Botrytis and Anthracnose Fruit Rot in Strawberries

Dr. Mengjun Hu, Univ. of Maryland, and Kathy Demchak, Penn State Extension

Managing gray mold (Botrytis) on strawberries is increasingly challenging because of fungicide resistance development, plus a new Botrytis species that is less susceptible to fungicides is becoming common in the mid-Atlantic region. Resistance to certain fungicides is also a problem in management of anthracnose fruit rot.  This article describes disease management strategies designed to slow further resistance development, while also providing specifics for managing our two most common fruit rots.

Gray mold on strawberry. Photo: Kathy Demchak, Penn State Extension

First, what’s new with Botrytis.  There are at least 4 species of Botrytis that can infect strawberries, but only two of them have been commonly found in the region. Botrytis cinerea, the species traditionally infecting strawberries, is present nearly everywhere and affects many horticultural crops.  Recently another species, Botrytis fragariae, has also been found and as its name indicates, is more specific to strawberry plants. It appears to overwinter on strawberry plant tissue, and preferentially colonizes blossoms early in the spring, causing them to “turn brown and dry up”.  While sometimes only one of these species is present, both can be present at the same time in a field and even in the same blossom.  Using certain fungicides selects for resistant strains of either species, and also preferentially selects for one species over the other.  This means that both species have resistance to multiple fungicide groups, and both species can survive in fungicide-treated fields.

How can you tell if the newer species of Botrytis might be present in your fields?  While B. cinerea (the traditional species) is often isolated from both flowers and fruit, B. fragariae (the new one) is often isolated from flowers, and it has been shown that B. fragariae infection was much more aggressive on strawberry flowers than fruit. If you see larger-than-usual numbers of blossoms turning brown and shriveling (not to be confused with frost damage, which blackens the center of the flower), it may be prudent to choose fungicides as if B. fragariae presence had been confirmed in your field.  If you see no more symptoms on the flowers or buds than usual, you may be able to assume that the new species isn’t present, or at least not to a great extent.

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Blueberry IPM Post Bloom – Diseases Pathogens

Emily Zobel on

By Haley Sater
Agriculture Agent, Wicomico County
University of Maryland Extension
HSater@umd.edu

( Article from May 2021 issues of UME Fruit and Vegetable Newsletter)

Most blueberry cultivars here in Maryland bloomed and green fruit are developing. Now is the time when a variety of pathogens and pest will begin to take up residence in your field which can harm your developing crop. It is important to perform routine scouting throughout your farm and make sure that you’re not seeing symptoms of some of
the common pests and pathogens. Below is a description of several of the most common diseases and pests you may find at this time in your blueberries.

Pathogens to be on the lookout for:
During the cool, wet days where temperatures do not reach above 70 degrees you may begin to see symptoms of several fungal pathogens including botryosphaeria canker or stem blight, botrytis, anthracnose and powdery mildew. These conditions make for an ideal environment for some of these fungal pathogens to grow or spread.

Blueberry Pathognes
A.)  Botryosphaeria stem blight, Bill Cline NCSU.  B.) Botrytis, Caleb Slemmons, National Ecological Observatory Network. C.) Anthracnose, Bruce Watt, University of Maine D.)  Powdery Mildew, Florida Dept. of Agriculture. Bugwood.org

Botryosphaeria stem blight (A) will exhibit dieback symptoms. It is initially detectable as yellowing and reddening of leaves which will move down then stem as vascular tissue becomes blocked by the pathogen. Whereas, botryosphaeria canker will develop as stem lesions which will sometime become swollen resulting in the formation of a canker. If botryosphaeria stem blight or canker is observed the best method to prevent the spread is pruning the infected tissue and fruit clusters six inches below any infected stems. Then, remove pruned branches from the field.

Botrytis (B) also known as gray mold, affects both fruit and the plant. It infects the fruit from bloom. As with botryosphaeria, the best tactic to reduce the spread of this disease is by pruning out infected fruit clusters and wood, then removing clippings from the field.

Anthracnose (C) will appear as stem, bud and leaf lesions and may have orange spore masses. Infections will cause leaf browning and will move from top of the leaf to the bottom. If untreated, anthracnose will also cause fruit rot. Fungicides may be used to prevent further development of anthracnose during the green fruit
development stage.

Powdery mildew (D) will start as chlorotic discoloration spots and develop into powdery masses on leaves. The infection usually begins in the spring with young leaves and may become more severe throughout the season eventually causing defoliation. However, while unsightly, powdery mildew will not significantly damage the developing fruit crop and therefore no action is required.