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 …
What does hail injury look like on apples, and what can I do when it happens?
Hail can injure apple fruit, shoots, and limbs. The extent of the injury usually depends on the size of the hail, its shape, and the duration of the event. Injury can range from torn or shredded leaves and small dents that don’t break the fruit skin to so severe that an entire crop is lost because of physical damage. In some cases, replacement of trees will be necessary, especially when young trees have large amounts of bark injury. Fungicide protection …
What is Powdery Mildew and how do I identify and manage the disease on apple trees?
Powdery mildew on apple is a fungus disease caused by Podosphaera leucotricha. It can be a persistent disease of susceptible apple cultivars wherever apples are grown. It is the only fungal apple disease that is capable of infecting without wetting from rain or dew. Mildew severity and the need for control measures are related to cultivar susceptibility and intended fruit market. For more information and images, read this article on Powdery Mildew on apple trees.
Answer provided by Alan …
What is sooty blotch, and how do I identify and manage the disease on apple trees?
Sooty blotch and flyspeck are surface blemish diseases caused by fungi that commonly appear together on apple or pear in late summer and fall. Although these diseases may shorten the storage life of fruit due to increased water loss, they do not cause decay, and losses are attributed to unacceptable appearance. During wet growing seasons, losses of 25% or more are commonly found even in orchards treated with fungicides. Many fungi are involved in this complex of pathogens, including Peltaster …
What is Brooks spot, and how do I identify and manage the disease?
Brooks spot is a fungus disease caused by Mycosphaerella pomi. It is a minor disease that occurs throughout the northeastern and mid-Atlantic apple growing regions of the United States and occasionally as far west as Iowa. Some of the more susceptible common commercial cultivars include ‘Jonathan’, ‘Golden Delicious’, ‘Stayman’, ‘Grimes Golden’, and ‘Rome Beauty’. Read more about Brooks Spot in Apple.
Answer provided by Alan R. Biggs, West Virginia University.…
What is fire blight, and how do I identify and manage the disease?
Fire blight is a destructive bacterial disease of apples and pears that kills blossoms, shoots, limbs, and, sometimes, entire trees. The disease is generally common throughout the United States wherever apples are grown, although outbreaks are typically very erratic, causing severe losses in some orchards in some years and little or no significant damage in others. This erratic occurrence is attributed to differences in the availability of overwintering inoculum, the specific requirements governing infection, variations in specific local weather conditions, …
I want to espalier an apple tree along a garage wall. What rootstock should I use?
Espalier is a technique of pruning and training apples in two dimensions, usually against a flat surface such as a wall or fence. The rootstock that you choose needs to induce enough vigor in the scion cultivar so that growth occurs but does not produce a tree with too much vigor. The environment where you are located will alter this decision. The colder, northern areas of the United States — that is, USDA hardiness zones 3 and 4 (look up …
What is fly speck, and how do I identify and manage the disease?
Fly speck and sooty blotch are surface blemish diseases caused by fungi that commonly appear together on apple or pear in late summer and fall. Although these diseases may shorten the storage life of fruit due to increased water loss, they do not cause decay, and losses are attributed to unacceptable appearance. During wet growing seasons, losses of 25% or more are commonly found even in orchards treated with fungicides. Many fungi are involved in this complex of pathogens, including …