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 diseases are problematic when planting apple trees in heavy soils?
Heavy soils are those that contain more clay particles relative to sand and silt components. The high clay content causes the soils to be less friable, making them “sticky,” and more dense, thus making them hard to work with. They often remain cold and wet in spring and need grit or coarse organic material to admit air and help roots remain healthy. Because of their tendency to be cold and wet for longer periods than lighter soils, there is an …
Which apple rootstocks are susceptible to fire blight?
Consider the relative susceptibilities of the scion and rootstock to fire blight when establishing new orchards. There is considerable variation among apple cultivars (and pear cultivars) in susceptibility to fire blight, although none are immune. Some cultivar/rootstock combinations are so susceptible to fire blight that investments in these combinations are extremely high risk. In the eastern United States, ‘Gala’ on M.26 is an example of a high-risk combination. For more information, read this article on Fire Blight of Apple.…
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.…
What is apple union necrosis and decline, and how do I identify and manage the disease?
Apple union necrosis and decline is caused by tomato ringspot virus, which also causes disease in other fruit trees, small fruits, and many herbaceous plants. Symptoms appear as infected trees reach bearing age. Bud break is often delayed in the spring, and leaves are small and sparse with a dull, pale green color. Terminal shoot growth is reduced, with shortened internodes. Infected trees flower heavily and set large numbers of small, highly colored fruit. Leaf discoloration and leaf drop occur …
What is quince rust, and how do I identify and manage the disease on apple trees?
Quince rust is a fungus disease caused by Gymnosporangium clavipes. The fungus infects fruit, but not leaves, of most apple cultivars. It infects both leaves and fruit of hawthorn. Typically, an infection on apple fruit shows up first as a slightly raised purplish area on the calyx end of the fruit. On mature fruit, the lesion is sunken and dark green or purple. Usually, the entire calyx end of the fruit is involved, and the flesh is deformed to …
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.…
What is Nectria canker, and how do I identify and manage the disease on apple trees?
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 …
What is X-spot, and how do I identify and manage the disease on apple trees?
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, …
What is blister spot, and how do I identify and manage the disease?
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.
Answer provided …