Diagnostic Guide to Common Home Orchard Diseases (B 1336) University of Georgia Extension This publication is intended to be used as a pictorial diagnostic guide to identify the most common diseases seen on fruits grown in home landscapes, gardens, and/or orchards in Georgia. Use this guide as a supplemental resource and/or reference to the Homeowner Edition of the Georgia Pest Management Handbook. 2015-09-29 17:38:51.833 2008-02-14 15:06:30.0 https://secure.caes.uga.edu/extension/publications/images/primary-pub-images/orcharddisease.png Diagnostic Guide to Common Home Orchard Diseases | Publications | UGA Extension Skip to content

Diagnostic Guide to Common Home Orchard Diseases (B 1336)

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Holly Thornton, Homeowner IPM Specialist
Dr. Phil Brannen, Extension Plant Pathologist

Introduction

This bulletin is intended to be used as a pictorial diagnostic guide to identify the most common diseases seen on fruits grown in home landscapes, gardens, and/or orchards in Georgia. Refer to the Homeowner Edition of the Georgia Pest Management Handbook for chemical control recommendations.

In terms of plant disease management in home orchards, an integrated pest management (IPM) approach is necessary to manage plant pathogens and ensure production of quality produce. Using clean plant stock, selecting disease-resistant varieties (when available), sanitation, proper cultural care and control, and maintaining healthy plants are all essential components in minimizing home orchard plant diseases. Most fungicides are largely protectant in nature and must be applied before symptoms are seen.

Keeping records or a journal of past plant diseases will be useful in managing future problems in the home orchard. Remember, when applying pesticides, read the chemical label carefully and follow all instructions written on the label. More specifically, take note of the Preharvest Intervals (PHI – interval of time between when the last chemical spray is applied and when the fruit is harvested) for each individual chemical. The PHI will vary depending on the chemical used.

Apples and Pears

Sooty blotch and fly speck

Sooty blotch and fly speck

Diagnostic features: Dull black sooty blotches and individual“fly specks”

Pathogen: Multiple organisms that usually occur together as a disease complex, referred to as SBFS (Peltaster fructicola, Geastrumia polystigmatis, and Leptodontium elatius – sooty blotch; Zygophiala jamaicensis – fly speck)

Comments: This disease complex appears late in the summer/early fall. Pruning is important to increase air circulation. Fruit thinning is also important. Diseases favor moderate temperatures and high humidity. These are superficial diseases, and they do not cause rots. Application (rubbing with a cloth) of a bleach solution (1 ounce household bleach per gallon of water) will help to remove these, but subsequent shelf life of apples is reduced.

Bitter rot

Bitter rot concentric rings
Bitter rot V-shaped lesions

Diagnostic features: Concentric rings of acervuli; V-shaped lesions extending to core of fruit

Glomerella cingulata
Conidia
(J. Brock, UGA)

Pathogen: Glomerella cingulata

Comments: This is a very important summer disease, especially when conditions are warm and moist! Pustules of spores are formed in concentric rings on the fruit. A sunken, sour-smelling rot results. Good sanitation is vital to management. Remove diseased fruit, which will hang on the tree, and any cankers formed in the woody tissues.

Black rot

Black rot

Diagnostic features: Brown, bruised-look on the calyx end of fruit

Botryosphaeria (Physalospora) obtusa
Conidia

Pathogen: Botryosphaeria (Physalospora) obtusa

Comments: A major disease on both apples and pears in the Southeast. On leaves, a symptom known as "frogeye" leaf spot occurs. Infection occurs early in the season at silver tip; rots become evident in the late season at the calyx or bottom end. Rot will be seen as concentric rings, and it will be dark (eventually turning black). Good sanitation is important, so prune out dead wood and remove fallen debris.

Apple scab

Apple scab
Apple scab

Diagnostic features: Black, scabby lesions on leaves and fruit

Venturia inequalis
Perithecia and spores

Pathogen: Venturia inequalis

Comments: Not a consistent problem in the Southeast. Cool, wet weather favors infection. Fruit and foliage must be protected season-long for adequate management if the disease does occur. Plant resistant varieties (ask local nurseries for availability). Sanitation is important. Rake and destroy fallen leaves to reduce the amount of disease that will carry over to the next year.

White or bot rot

White or bot rot

Diagnostic features: Depressed, soft enlarged lesion on fruit

Botryosphaeria dothidea
Ascospores within asci

Pathogen: Botryosphaeria dothidea

Comments: This is a serious and common late-season problem in apples and pears. This fruit rot is a rapidly developing soft rot (unlike bitter rot and black rot, which form harder rots). Sanitation is important. Remove mummified apples (dried, dead apples hanging in the tree) and prune out deadwood.

Fire blight

Fire blight
Fire blight

Diagnostic features: Shepard’s crook symptom on foliage; dieback on branch due to presence of a canker

Pathogen: Erwinia amylovora - Bacterial disease

Comments: This is a bacterial disease, and it is very destructive on both apples and pears. It's difficult and expensive to control. Avoid spraying too often, as resistance may develop. Succulent tissues are most vulnerable to infection, so avoid excessive nitrogen fertilization. Avoid pruning during and after the blossom period (corresponds to insect feeding). Promptly prune out any blighted tissue; remove infected plant parts through cutting 8 to 12 inches below diseased tissue; between cuts, disinfect pruning tools using a 10 percent bleach solution.

Cedar-apple rust

Cedar-apple rust
Cedar-apple rust

Diagnostic features: Lesions on apple leaves; telial gall on cedar (alternate host)

Gymnosporangium juniperi- virginianae
Teliospores

Pathogen: Gymnosporangium juniperi-virginianae

Comments: Can cause extensive defoliation of apple trees. Plant resistant varieties! If possible, remove galls from nearby cedar trees (breaks the fungal life cycle, as it needs both hosts to reproduce).

Blueberries

Botrytis blight

Botrytis blight
Botrytis blight
(Bill Cline, NCSU)

Diagnostic features: Blighted flowers (covered in conidia); berries covered in conidia

Botrytis cinerea
Conidiophore and conidia

Pathogen: Botrytis cinerea

Comments: Disease affects green twigs, flowers, leaves and fruit. Outbreaks often occur after freeze injury to flowers in the spring, especially when followed by cool, wet weather. Fruit rot does not generally occur until after fruit is harvested. Sanitation is important. Remove infected fruit/mummies and maintain a good mulch layer.

Mummy berry

Mummy berry
(H. Scherm, UGA)
Mummy berry
(Bill Cline, NCSU)
Monilinia vaccinii-corymbos
(H. Scherm, UGA)
Monilinia vaccinii-corymbos
(H. Scherm, UGA)
Mummy berry
(Bill Cline, NCSU)

Diagnostic features: Shoot blight; mummified berries; apothecia

Monilinia vaccinii-corymbos
Conidia

Pathogen: Monilinia vaccinii-corymbosi

Comments: Sanitation is important; rake and remove mummies (dead fruit on the ground); prune annually.

Septoria leaf spot

Septoria leaf spot
(Bill Cline, NCSU)

Diagnostic features: Small leaf spots with tan center and purple border (black dot in center – pycnidia of pathogen)

Septoria albopunctata
Narrow, filiform several-celled conidia

Pathogen: Septoria albopunctata

Comments: Rake and remove infected leaf debris. Summer pruning or topping will help remove older, infected tissues. Increased spacing will improve air circulation, resulting in dryer foliage.

Twig blight and fruit rot

Fruit rot
(Bill Cline, NCSU)
Twig blight
(Bill Cline, NCSU)

Diagnostic features: Dieback of blueberry twigs, rotting berries

Phomopsis vaccinii
Conidia (two types: alpha [oval or fusoid] and beta [long and curved])

Pathogen: Phomopsis vaccinii

Comments: Twig blight – remove infected twigs in winter; choose resistant cultivars when available. Fruit rot – harvest fruit before it becomes overripe.

Brambles (Raspberries and Blackberries)

Anthracnose

Anthracnose
(NCSU/PDIC, courtesy Bill Cline)

Diagnostic features: Small, purplish or tan, slightly raised
or sunken spots along young canes

Pathogen: Elsinoe veneta

Comments: Disease affects canes, leaves, fruit and stems of berry clusters. Symptoms on canes are ash grey lesions with raised purple to brown borders. Sanitation is very important. After harvest, cut old floricanes to the ground, and remove and destroy them.

Orange rust

Orange rust
Orange rustOrange rust of blackberry, aecial stage (Charles Mims, UGA CAES Department of Plant Pathology)

Diagnostic features: Yellow-orange pustules on leaf surfaces (usually lower leaf)

Kunkelia nitensOrange rust of blackberry, spermogonial stage (Charles Mims, UGA CAES Department of Plant Pathology)
Kunkelia nitens
Spores

Pathogen: Kunkelia nitens

Comments: Attacks all brambles except red raspberries. Establishes a systemic infection and, once infected, no cure is available. Symptoms include stunting and limited fruit production. Symptoms occur shortly after leafing out. When disease is first detected, dig up and discard/destroy any infected plants to reduce spread.

Rosette or double blossom

Rosette

Diagnostic features: Bunchy growth at nodes

Cercosporella rubi
Spores

Pathogen: Cercosporella rubi

Comments: Most damaging to blackberries. In the spring, infected buds from the previous year produce numerous leafy sprouts — "rosettes" or "witches brooms." Berries do not develop from infected blossoms. Remove/destroy nearby wild brambles — they serve as reservoirs; remove infected rosettes and blossom clusters before they open.

Orange felt (orange cane blotch)

Orange felt

Diagnostic features: Yellow, disc-shaped spots on canes

Cephaleuros virescens
Algal sporangiophores

Pathogen: Cephaleuros virescens

Comments: Remove old floricanes after harvest; increase air circulation in canopy; avoid stressing plants; improve drainage.

Cane blight

Cane blight

Diagnostic features: Dieback of canes

Pycnidia
Pycnidia
Ascospores in ascus
Ascospores in ascus

Pathogen: Leptosphaeria coniothyrium

Comments: Remove old floricanes after harvest; increase air circulation in canopy; avoid stressing plants; improve drainage. Sanitation is very important. Remove dead and infected canes during and after harvest. Avoid stressing plants. During the summer, prune by pinching off tender primocanes when they reach 3-4 feet high. Remove 1-4 inches of primocane tip; avoid making severe pruning cuts on older tissues. Do not prune ahead of predicted rains; prune when 3-4 days of dry conditions are predicted.

Bunch Grapes

Black rot

Black rot
Black rot
Black rot

Diagnostic features: Small, yellowish spots on leaves; sunken oval lesion with pycnidia of the fungus (black dots); shriveled mummies (infected berries)

Guignardia bidwellii
Pycnidia in a mummified grapevine berry

Pathogen: Guignardia bidwellii

Comments: Annual pruning in February; removing infected berries both on the ground and on the plant. After pruning, only the permanent trunk, one-year-old fruiting canes and short spurs should remain. Sanitation is important. Remove mummified fruit! Disease spread is favored by moist, wet weather.

Powdery mildew

Powdery mildew

Diagnostic features: White powdery fungal growth on berries

Uncinula necator
Conidia
Uncinula necator
Cleistothecia

Pathogen: Uncinula necator

Comments: Annual pruning in February will help to remove inoculum; remove infected berries both on the ground and on the plant. After pruning, only the permanent trunk, one-year-old fruiting canes and short spurs should remain.

Downy mildew

Downy mildew

Diagnostic features: Yellow, irregular-shaped lesions on upper surface; whitish-gray fungal growth directly under lesions on lower surface of leaves

Plasmopara viticola
Conidiophores
Plasmopara viticola
Conidia

Pathogen: Plasmopara viticola

Comments: Annual pruning in February; remove infected berries both on the ground and on the plant. After pruning, only the permanent trunk, one-year-old fruiting canes and short spurs should remain.

Pierce’s disease

Pierce's disease

Diagnostic features: Scorched leaves with a defined margin and yellow/chlorotic border

Pathogen: Xylella fastidiosa - Bacterial disease

Comments: Vectored by various sharpshooters (such as glassywinged sharpshooter). New growth is stunted, yellow, deformed (resembles zinc deficiency). Choose more resistant cultivars; native grapes are generally more resistant. Do not propagate from symptomatic vines. Do not plant vinifera wine or table grapes at elevations below 1,300 feet. Muscadines are generally resistant, and some other native grapes have limited resistance.

Phomopsis

Phomopsis

Diagnostic features: Small, black pycnidia of the fung

Status and Revision History
Published on Feb 14, 2008
Re-published on Oct 9, 2009
Re-published on Feb 18, 2011
Reviewed on May 29, 2015