What is Nectria canker, and how do I identify and manage the disease on apple trees?

Nectria canker is a fungus disease caused by Nectria galligena. It is occasionally found on apple nursery stock shipped into the eastern United States. The economic effects of the disease in the eastern United States are minor.┬áThe fungus grows deep into the wood and kills new wound callus as it develops. This annual killing of successive layers of callus results in perennial, target-like, zonate cankers. Eventually the cankers girdle the tree, resulting in a dieback of infected limbs …

What is X-spot, and how do I identify and manage the disease on apple trees?

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. 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’. A fungus has been associated with X-spot lesions, but the typical lesion symptom has not been duplicated by controlled inoculation, …

What is blister spot, and how do I identify and manage the disease?

Blister spot is a bacterial disease of apple fruit caused by Pseudomonas syringae pv. papulans. This disease is of economic importance mainly on the cultivar ‘Mutsu’ (‘Crispin’) but can be seen on ‘Golden Delicious’ when grown adjacent to ‘Mutsu’. Even though fruit grow to maturity and no detectable yield loss occurs, severe infection results in ugly fruit and greatly reduces fresh market quality. For more information and images, read this article on Blister Spot of Apple.

Answer provided …

What is Nectria twig blight, and how do I identify and manage the disease?

Nectria twig blight is a fungus disease that results in dieback of apple twigs. It is caused by the fungus Nectria cinnabarina. Recognition of the disease is important because it is often confused with fire blight, which requires different control measures. For more information and images, read this article on Nectria Twig Blight of Apple.

Answer provided by Alan R. Biggs, West Virginia University.…

What is black rot, and how do I identify and manage the disease on apple trees?

Black rot is a fungus disease that can cause serious losses in apple orchards, especially in warm, humid areas. Three forms of the disease can occur:

  • a fruit rot, which causes fruit to become unmarketable;
  • a leaf spot known as frogeye leaf spot which, if severe, can result in defoliation which weakens the tree; and
  • a limb canker which can girdle and eventually kill entire branches.

Read more and see images in this article, Black Rot of Apple.…

What is cedar-apple rust, and how do I identify and manage the disease?

Cedar-apple rust is a fungus disease of apple and cedar and spends parts of its life cycle on each host. It is caused by Gymnosporangium juniperi-virginianae. The fungus can infect leaves and fruit of most cultivars in the eastern region. A notable exception is ‘Delicious’, which is nearly immune. For more information, see this article on Cedar-Apple Rust.

Answer provided by Alan R. Biggs, West Virginia University.…

What is white root rot in apple trees?

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 is found 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, …

What is apple mosaic virus, and how do I identify and manage the disease?

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

What is bitter rot, and how do I identify and manage the disease?

Bitter rot is a fungus disease that causes fruit rot during the summer and preharvest period. The bitter rot fungi are almost worldwide in distribution and cause an especially economically important disease in the southern areas of the United States. Outbreaks can occur rapidly, and losses can be severe, especially under prolonged warm, wet weather. Several host species can be affected. On peach and nectarine, the same fungus causes a disease known as anthracnose, and on grape, it causes ripe …