Thread blight is a fungus disease caused by Corticium stevensii. The disease is primarily a problem in poorly managed orchards in the southeastern United States. Thread blight symptoms are readily noticed in early summer. Leaves wilt and turn brown, usually in the interior or shaded portions of the tree. Dead, curled leaves cling to blighted branches, frequently in mid-branch, with unaffected leaves still appearing on both sides of the diseased area. In well-managed orchards, the disease is usually not …
What is white rot, and how do I identify and manage the disease on apple trees?
White rot is often referred to as Botryosphaeria rot or Bot rot and is caused by Botryosphaeria dothidea, a serious fungal pathogen of apple fruit and wood. The fungus causing white rot is ubiquitous in nature, occurring on a wide variety of woody plants including birch, chestnut, peach, and blueberry. Fruit rot infection is most common in areas of the southeastern United States where losses of up to 50% have been reported. The canker phase of the pathogen can …
What are wood rots in apple trees?
Wood-rotting fungi cause losses over longer periods of time than most other diseases. Losses are caused mainly by breakage of branches and trunks due to a decline in the structural integrity of the wood. Structural integrity of the wood is altered by the enzymatic digestion of wood cell-wall components by the fungal pathogen or pathogens that have colonized the wood. Some of the same fungi that cause wood rot can also cause dieback. Learn more and see images in this …
What is 'Golden Delicious' necrotic leaf blotch, and how do I identify and manage the disease?
Necrotic leaf blotch (NLB) is a physiological disorder whose occurrence is related to air temperature, light intensity, and soil moisture. The cause of NLB of apple is not known. A hormonal imbalance may be involved because symptoms are enhanced by gibberellins and reduced by abscisic acid. The disorder occurs worldwide on ‘Golden Delicious’ and its bud sports. ‘Golden Delicious’ seedlings vary in susceptibility. ‘Prime Gold’ and ‘Nugget’ are also affected by NLB. For more information, read this article on ‘Golden …
Will an apple tree grow differently if I plant the graft union high above the soil or close to the ground?
The planting depth is critical, especially for trees on dwarf or semi-dwarf rootstocks. When planting, dig the hole deep enough to allow the tree to be planted with the graft union 2 to 3 inches above the ground. If the tree is planted too deep and the graft union is below the ground level, the scion variety will form roots and the tree will become a standard-sized tree. Also, if the graft union is buried, the tree may send up …
Do trees planted on dwarfing rootstocks produce small apples?
Without question, a dwarfing rootstock can reduce vegetative growth, resulting in a tree with a smaller trunk, shorter height, narrower canopy, and lower root volume. These rootstocks, however, do not reduce size of leaves, flowers, or fruit. Nearly all NC-140 apple rootstock trials have evaluated rootstock effects on fruit size, and, in some cases, rootstock did in fact affect size. In no case was the relationship between the degree of dwarfing and fruit size such that the more dwarfing the …
What is apple scab, and how do I identify and manage the disease?
Apple scab is a fungus disease caused by Venturia inaequalis. It is of major economic importance and, if not controlled, the disease can cause extensive losses (70% or greater) where humid, cool weather occurs during the spring months. Losses result directly from fruit or pedicel infections or indirectly from repeated defoliation, which can reduce tree growth and yield. For more information, read this article on Apple Scab.
Answer provided by Alan R. Biggs, West Virginia University.…
Why can’t I plant seeds from my apple?
You can plant seeds from your apple, but the resulting fruit from that seedling will not be exactly like the apple parent. Most apple seeds are formed when pollen from one apple cultivar pollinates the flower of another cultivar. This results in the combination of two different genetic parents and results in an offspring (seed) that has a different genetic code. The resulting seed and potential tree will have characteristics of both the pollen parent and the flowering parent. Therefore, …
Why are rootstocks used for apple trees?
Apples do not come true from seed, so when we plant apple seeds, the plants that result are not the cultivar that we obtained the seeds from. If we take six seeds from an apple and plant them, the resulting trees will produce fruit that is different from fruit on the parent tree, and the seedlings will be different from each other. To maintain a cultivar, we have to propagate the tree vegetatively. Since apple cuttings are difficult to root, …
Why do nurseries use budding versus grafting?
Budding is often used because a single scion bud is inserted into the rootstock to produce a new tree. Also, with budding, many trees can be produced from a stick of bud wood that has different sized buds.
In contrast, a piece of scion wood with two buds is used in grafting, and the diameter of the rootstock and the scion piece must match precisely to form a union. Thus, fewer trees can be propagated by grafting as compared to …