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 …
What is southern blight in apple trees?
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.…
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 …
What is blue mold, and how do I identify and manage the disease?
Blue mold is a fungus disease caused by Penicillium expansum. It is the most important postharvest decay of stored apples in the United States. The losses from this disease can be significant but can be substantially reduced by following proper sanitation and control measures. The fungus not only causes fruit decay but also produces the carcinogenic mycotoxin patulin. This toxin may rise to unacceptable levels in fruit destined for processing and may also result in off flavors. For more …
When should apple trees be budded?
Budding time will depend on where you live and the type of budding technique you use. Traditional timing in the northern hemisphere above 36 degrees latitude, roughly the Virginia-North Carolina border, would be to bud trees in late August to early September, when the bark readily “slips.” Slipping refers to the ability of the bark to be easily and smoothly pulled away from the heartwood of the tree. When this occurs, “T-budding” or “chip budding” can be performed. If you …
How do I identify and manage Armillaria root rot, or shoestring rot, in apple?
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 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.…