Tag: apple disease

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X-Spot of Apple

The names X-spot, X-rot, and Nigrospora spot have been applied to a small, circular, depressed, necrotic spot typically on the calyx end of apple fruit in the mid-Atlantic region (Fig. 1). Although uncommon, incidence of X-spot as high as 86% was reported on unprotected ‘Golden Delicious’ and ‘Rome Beauty’ fruit in 1950. Other susceptible cultivars include ‘Jonathan’, ‘Stayman Winesap’, and ‘York Imperial’.

Figure 1. X-spot is likely a fungal disease, although the pathogen is undetermined at this time. Photo: A.
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Black Rot of Apple

Black rot is a fungus disease that can cause serious losses in apple orchards, especially in warm, humid areas. The black rot fungus covers a wide geographical range and can infect many hosts other than apple. The role these hosts play in the spread and development of the disease is not known. Three forms of the disease can occur: a leaf spot known as frogeye leaf spot, a fruit rot, and a limb canker. Severe leaf spotting can result in …

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Fire Blight of Apple

Fire blight

Figure 1. Blossom cluster and adjacent shoot with fire blight. (Alan R. Biggs, West Virginia University)

Fire blight is a destructive bacterial disease of apples and pears that kills blossoms, shoots, limbs, and, sometimes, entire trees (Figs. 1, 2). The disease is generally common throughout the United States wherever apples are grown. Outbreaks are typically very erratic, causing severe losses in some orchards in some years and little or no significant damage in others.

Fire blight

Figure 2. Apple shoot with fire …

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Table of Apple Cultivar Susceptibility to Bitter Rot

 

Bitter rot is a fungus disease that causes fruit rot during the summer and the preharvest period. The bitter rot fungi are almost worldwide in distribution and cause an especially economically important disease in the southern United States. Outbreaks can occur rapidly, and losses can be severe, especially under prolonged warm, wet weather. This table lists the bitter rot susceptibility rating of many popular apple cultivars.

Apple cultivar

Bitter rot
susceptibility ratingz

 Apple cultivar

Bitter rot
susceptibility ratingz

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Table of Apple Cultivar Susceptibility to Quince Rust

 

Quince rust is a fungus disease caused by Gymnosporangium clavipes. The fungus infects fruit, but not leaves, of most apple cultivars. It infects both fruit and leaves of hawthorn. This table lists the quince rust susceptibility of numerous apple cultivars.

Apple cultivar Quince rust
susceptibility ratingz		 Apple cultivar Quince rust
susceptibility ratingz
Ambrosia HS Milton R
Arkansas Black HS Mutsu R
Arlet S Northern Spy R
Baldwin R Orin R
Ben Davis R Paulared R
Braeburn S Pinova
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White Root Rot of Apple

White root rot, caused by the fungus Scytinostroma galactinum (formerly Corticium galactinum), has been known as a parasite of apple trees for many years and is widely distributed (Canada to Texas and westward to the Pacific coast, Europe, West Indies, and Japan). It occurs in both bearing and non-bearing apple orchards. Other hosts include a wide variety of woody plants, ornamental shrubs, and herbaceous perennials, including white pine, ash, peach, blackberry, dewberry, Japanese wineberry, dogwood, sumac, white campion, holly, …

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Apple Mosaic Virus

Apple mosaic virus is one of the oldest known and most widespread apple viruses. The same virus can cause line pattern symptoms in plum and rose mosaic disease. Apple mosaic virus is related to Prunus necrotic ring spot virus.

Apple trees infected with apple mosaic virus develop pale to bright cream spots on spring leaves as they expand (fig. 1). These spots may become necrotic after exposure to summer sun and heat. Most commercial cultivars are affected, but severity of …

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Thread Blight of Apple

Thread blight is a fungus disease caused by Corticium stevensii. Primarily, the disease is a problem in poorly managed orchards in the southeastern United States.

Thread blight symptoms are noticeable in early summer. Leaves wilt and turn brown (fig. 1), usually on the interior or shaded portions of the tree. Dead, curled leaves cling to blighted branches, frequently mid-branch, with unaffected leaves remaining on both sides of the diseased area (fig. 2). In well-managed orchards, the disease usually does not …

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White Rot of Apple

White rot is often referred to as Botryosphaeria rot or Bot rot and is caused by Botryosphaeria dothidea, a serious fungal pathogen of apple wood and fruit. The fungus causing white rot is ubiquitous in nature, occurring on a wide variety of woody plants, including birch, chestnut, peach, and blueberry. The canker phase of the pathogen can cause considerable loss in many parts of the South, Midwest, and Northeast. Fruit rot infection is most common in areas of the southeastern …

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Wood Rots in Apple Trees

Wood-rotting fungi cause losses over longer periods of time than most other apple diseases. Losses result mainly from breakage of branches and trunks due to a decline in the structural integrity of the wood. Fungal pathogens that colonize wood alter its structural integrity through enzymatic digestion of wood cell wall components. Some of the same fungi that cause wood rot can cause dieback as well.

The two most common symptoms of wood rot are the breakage of limbs or main …

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