Armillaria root rot, also known as shoestring root rot, is a soilborne disease that can affect several fruit crops, but it is most common in the eastern United States on peach and apple trees. Its host range also includes numerous species of deciduous and evergreen trees, shrubs, and woody vines. The greatest prevalence of the disease is in orchards planted on newly cleared land in which the soils are sandy and well drained. In these locations, pieces of wood invaded …
What is black root rot (dead man’s fingers), and how do I identify and manage the disease?
Black root rot, also called dead man’s fingers or Xylaria root rot, is occasionally observed on mature apple and cherry trees. Although trees of all ages can be infected, most trees that die from black root rot are at least 10 years old. Black root rot is caused by two species of the fungus Xylaria, X. mail and X. polymorpha, with the former being more common in the southern Appalachian states, and the latter more common in the eastern …
What is apple union necrosis and decline, and how do I identify and manage the disease?
Apple union necrosis and decline is caused by tomato ringspot virus, which also causes disease in other fruit trees, small fruits, and many herbaceous plants. Symptoms appear as infected trees reach bearing age. Bud break is often delayed in the spring, and leaves are small and sparse with a dull, pale green color. Terminal shoot growth is reduced, with shortened internodes. Infected trees flower heavily and set large numbers of small, highly colored fruit. Leaf discoloration and leaf drop occur …
What is quince rust, and how do I identify and manage the disease on apple trees?
Quince rust is a fungus disease caused by Gymnosporangium clavipes. The fungus infects fruit, but not leaves, of most apple cultivars. It infects both leaves and fruit of hawthorn. Typically, an infection on apple fruit shows up first as a slightly raised purplish area on the calyx end of the fruit. On mature fruit, the lesion is sunken and dark green or purple. Usually, the entire calyx end of the fruit is involved, and the flesh is deformed to …
What is black pox, and how do I identify and manage the disease?
Black pox is a fungus disease caused by Helminthosporium papulosum. It is considered to be of minor economic importance. When it occurs, the disease can affect apple bark, fruit, and foliage. It is more common from southern Virginia southward than in the northern mid-Atlantic region. The same fungus causes blister canker on pear. For more information, read this article on Black Pox of Apple.
Answer provided by Alan R. Biggs, West Virginia University.…
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. The 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.…