The woolly apple aphid, Eriosoma lanigerum (Hausmann), is a reddish brown insect covered with a white wax mass produced by specialized dermal glands. This wax mass gives the insect its characteristic woolly appearance (fig. 1). The woolly apple aphid is distributed worldwide.
The most important form of injury caused by woolly apple aphids is root injury, consisting of galls at feeding sites (fig. 2). This root injury can reduce the growth of young apple trees; mature trees are affected to …
Apple Phytophthora root, crown, or collar rot has caused extensive death of apple trees in many eastern orchards during the past two decades. It often occurs on trees between 3 and 8 years of age grown on Malling-Merton 104 (MM.104), MM.106, and, to a lesser degree, MM.111 rootstocks. The disease often affects low areas of orchards having heavy, poorly drained soils, but it can affect all orchard sites if trees are first infected in the nursery. This table illustrates susceptibility …
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 (Fig. 1). 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’.
| Figure 1. X-spot is likely a fungal disease, although the pathogen is undetermined at this time. Photo: A. |
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Black rot is a fungus disease that can cause serious losses in apple orchards, especially in warm, humid areas. The black rot fungus covers a wide geographical range and can infect many hosts other than apple. The role these hosts play in the spread and development of the disease is not known. Three forms of the disease can occur: a leaf spot known as frogeye leaf spot, a fruit rot, and a limb canker. Severe leaf spotting can result in …
Hail can injure apple fruit, shoots, and limbs. The extent of the injury usually depends on the size and shape of the hail 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 effects so severe that an entire crop is lost due to physical damage. In some cases, replacement of trees is necessary, especially when young trees have significant bark injury. Fungicide protection of injured …
Many nurseries supply fruit trees to commercial and home growers. We’ve assembled lists of some of these nurseries to help you source particular plant material or locate nurseries in your region. As Cooperative Extension educators, our goal is to provide you with basic information and resources to make informed decisions. These lists are for informational purposes only. They are neither comprehensive nor intended to promote any individual businesses.
Figure 1. Blossom cluster and adjacent shoot with fire blight. (Alan R. Biggs, West Virginia University)
Fire blight is a destructive bacterial disease of apples and pears that kills blossoms, shoots, limbs, and, sometimes, entire trees (Figs. 1, 2). The disease is generally common throughout the United States wherever apples are grown. Outbreaks are typically very erratic, causing severe losses in some orchards in some years and little or no significant damage in others.
Figure 2. Apple shoot with fire …
White rot is often referred to as Botryosphaeria rot or Bot rot and is caused by Botryosphaeria dothidea, a serious fungal pathogen of apple wood and fruit. The fungus causing white rot is ubiquitous in nature, occurring on a wide variety of woody plants, including birch, chestnut, peach, and blueberry. The canker phase of the pathogen can cause considerable loss in many parts of the South, Midwest, and Northeast. Fruit rot infection is most common in areas of the southeastern …
Wood-rotting fungi cause losses over longer periods of time than most other apple diseases. Losses result mainly from breakage of branches and trunks due to a decline in the structural integrity of the wood. Fungal pathogens that colonize wood alter its structural integrity through enzymatic digestion of wood cell wall components. Some of the same fungi that cause wood rot can cause dieback as well.
The two most common symptoms of wood rot are the breakage of limbs or main …
A large number of latent viruses have been identified in apple. More common latent viruses include apple chlorotic leaf spot virus, apple stem pitting virus, and apple stem grooving virus. These viruses also cause diseases in other fruit crops. Apple chlorotic leaf spot virus causes pear ring pattern mosaic and has been found in all pome and stone fruit species. Apple stem pitting virus is the causal agent of pear vein yellows.
As the designation “latent” implies, these viruses are …