Southern blight is caused by the fungus Sclerotium rolfsii. The disease is a problem primarily in the Piedmont apple-growing region in the southeastern United States. S. rolfsii is a widespread pathogen that affects several hundred plant species. For more information, read this article on Southern Blight in Apple Trees.
Answer provided by Alan R. Biggs, West Virginia University.…
Results from a number of apple rootstock trials in different regions of North America indicate that some rootstocks can influence fruit size. Trees on M.7, G.16, and M.26 generally produce smaller fruit than trees on M.9. Most other tested rootstocks produce fruit slightly smaller than M.9. Although experiments have not been performed to compare fruit size from trees grown on semi-dwarf or non-dwarfing rootstocks, orchard observations indicate that fruit produced by trees on M.9 are larger than fruit produced by …
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:
Read more and see images in this article, Black Rot of Apple.…
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.…
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.
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Choosing the best dwarfing rootstock for your orchard will depend on multiple factors. Probably one of the most important is the cultivar that will be propagated on the rootstock. Cultivars vary greatly in vigor, with some being very weak growing (‘Honeycrisp’) compared to others that are very vigorous (‘Cripps Pink’/’Pink Lady’). You should select the cultivar/rootstock combination that will give you the desired tree size for your desired tree density, support system, soil, and management system.
The disease sensitivity of …
Burr knots are root initials that develop above ground. Rootstocks are selected for their ability to produce roots, but some rootstocks try to produce roots above the ground. The severity of burr knot development differs depending on the variety and region. In several rootstock trials, trees in Virginia tended to produce more burr knots than trees in most other locations. Sometimes several burr knots will coalesce and partially girdle the tree. Burr knots are considered undesirable because they can be …
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, …
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 …
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.…
