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Sun scald is the freezing of bark following high temperatures in the winter season, resulting in permanent visible damage to bark. Fruits may also be damaged. In the northern hemisphere, it is also called southwest injury. [1]
The reason the sun can cause so much damage to trees is because of dormancy. When a tree is dormant in the winter it can be reactivated by warm weather. In the northern woods trees are exposed to the most sunlight and heat on the southwest facing side, so this side is heated during warm sunny winter days (in the afternoon, that's why westwards) to the point that it can be awoken from dormancy. The temperature required to wake up a tree depends on plant species and length of day, but it is typically just above freezing. [2] Once active, the cells on the southwest side of the plant are unable to return to dormancy by nightfall, at which time the temperature returns to levels capable of killing active cells. Fluctuating winter temperatures can also cause frost cracks, which result from the expanding and contracting of the tree trunk.
When sun scald appears on trees it is most frequently a result of reflected light off the snow during winter months. The damage in this case will appear as sunken or dead bark on the trunk of the tree, then later in the tree's life the bark might fall away revealing dead tissue in the tree's cambium layer. This damage will typically be found on the south west facing side of the tree's trunk. It can be found on other sides of the tree if there is light reflection from other sources, like man made structures or reflective rock faces. After a tree is afflicted by sun scald it becomes much more vulnerable to decay organisms. The plant will create walls around the affected area, but sometimes it is not enough to block the infections. The leaves of the tree are also affected by sun scald, particularly on a bright sunny day following a period of warm cloudy humidity. The damage to the leaves will start as bronzing of the epidermis between the veins of the leaf, and if the sunny conditions persist the tissue of the leaf will die.
Sun scald on fruit appears when a fruit is exposed to direct sunlight after cold storage for an extended period of time, typically after harvest. The damage can often lead to the death of the fruit via consumption by insects, animals, bacteria, or fungi. This is the case if the defenses of the fruit are too heavily inflicted, which may occur when the outer skin is damaged to the point that the cell walls/membranes are either gone or weak enough for the plant's enemies to penetrate. Sun scald often presents as more of an internal damage, with the affected tissue gaining a leathery or wrinkled appearance and a pale discoloration. The terms "sun scald" and "sunburn" are frequently used interchangeably, however fruit sunburn is generally distinguished by only occurring pre-harvest and leaving yellow, bronze, or brown discoloration of the skin. [3] Fruits damaged to either extent are usually considered unmarketable due to diminished appearance, taste, and texture, but those of the latter are sometimes sold at a lower grade or utilized as an (often puréed) ingredient. Sun damage cannot be reversed, but the fruit may still be able to fend off attacks and partially recover if properly treated and protected from further damage.
The treatment of sun scalding is fundamentally simple: reduce the intensity of the sun, or block the sun completely.
The most common method used to prevent sun scalding on the trunks of trees is to wrap the tree up to the first branch with white paper overlapping approximately thirty three percent each time around the tree. The white paper is effective in reflecting the heat of the sun off the tree. The paper should be applied after the tree has gone dormant for the winter and taken off before it becomes active again. If the paper is left on too long it can interfere with the growth of the tree and harbor insects that may damage the tree.
Painting the tree white has the same effect as wrapping, although it is a permanent change to the color of the tree. This discoloration can be aesthetically displeasing, so this method is mostly used in orchards and rarely in landscaping.
The amount of light a tree receives on its southwest side is correlated with the amount of sun scald the tree endures. Reducing the amount of light the tree is exposed to by planting a shrub or bush strategically to shade the southwest side can be less effective than wrapping or painting, but can have better aesthetic qualities for landscaping.
For fruit the most important part of avoiding sun scald is to be aware of where the fruit has been during its growth. If the fruit grew in the shade then exposing it to the sun will be likely to yield damage to the produce. Because of the importance of keeping shaded fruits out of the sun, leaves of fruit plants should be monitored for wilting and disease. If the leaves that shade a fruit die, the fruit will be exposed and in danger of sun scald. Another measure that can be taken to avoid damage is covering the fruits with straw or screen to block the sun.
Frost is a thin layer of ice on a solid surface, which forms from water vapor that deposits onto a freezing surface. Frost forms when the air contains more water vapor than it can normally hold at a specific temperature. The process is similar to the formation of dew, except it occurs below the freezing point of water typically without crossing through a liquid state.
Dimocarpus longan, commonly known as the longan and dragon's eye, is a tropical tree species that produces edible fruit. It is one of the better-known tropical members of the soapberry family Sapindaceae, to which the lychee and rambutan also belong. The fruit of the longan is similar to that of the lychee, but less aromatic in taste. It is native to tropical Asia and China.
Acer rubrum, the red maple, also known as swamp maple, water maple, or soft maple, is one of the most common and widespread deciduous trees of eastern and central North America. The U.S. Forest Service recognizes it as the most abundant native tree in eastern North America. The red maple ranges from southeastern Manitoba around the Lake of the Woods on the border with Ontario and Minnesota, east to Newfoundland, south to Florida, and southwest to East Texas. Many of its features, especially its leaves, are quite variable in form. At maturity, it often attains a height around 30 m (100 ft). Its flowers, petioles, twigs, and seeds are all red to varying degrees. Among these features, however, it is best known for its brilliant deep scarlet foliage in autumn.
Meryta sinclairii, the puka or pukanui, is a large-leaved evergreen tree endemic to New Zealand that grows to about 8 m tall, with the distinctly tropical appearance typical of the genus. There are about 27 species of Meryta, all small, resinous trees of the subtropical and tropical Pacific Ocean.
A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of gymnosperms and dicotyledonous flowering plants. It functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases. The name lenticel, pronounced with an, derives from its lenticular (lens-like) shape. The shape of lenticels is one of the characteristics used for tree identification.
Mangosteen, also known as the purple mangosteen, is a tropical evergreen tree with edible fruit native to Island Southeast Asia, from the Malay Peninsula to Borneo. It has been cultivated extensively in tropical Asia since ancient times. It is grown mainly in Southeast Asia, southwest India and other tropical areas such as Colombia, Puerto Rico and Florida, where the tree has been introduced. The tree grows from 6 to 25 m tall.
Quercus suber, commonly called the cork oak, is a medium-sized, evergreen oak tree in the section Quercus sect. Cerris. It is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring and as the cores of cricket balls. It is native to southwest Europe and northwest Africa. In the Mediterranean basin the tree is an ancient species with fossil remnants dating back to the Tertiary period.
Alnus glutinosa, the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa. It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium-sized, short-lived tree growing to a height of up to 30 metres (98 feet). It has short-stalked rounded leaves and separate male and female flowers in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water.
Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots.
The tamarillo is a small tree or shrub in the flowering plant family Solanaceae. It is best known as the species that bears the tamarillo, an egg-shaped edible fruit. It is also known as the tree tomato, tomate de árbol, tomate andino, tomate serrano, blood fruit, poor man's tomatoe, tomate de yuca, tomate de españa, sachatomate, berenjena, chilto and tamamoro in South America, tyamtar, rambheda or rukh tamatar in Nepal, and terong Belanda in Indonesia. It is popular globally, especially in Peru, Colombia, New Zealand, Ecuador, Nepal, Rwanda, Burundi, Australia, Bhutan and the United States.
A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticulture. Their causes include a wide range of organisms as fungi, bacteria, mycoplasmas and viruses. The majority of canker-causing organisms are bound to a unique host species or genus, but a few will attack other plants. Weather and animal damage can also cause stress to the plant resulting in cankers. Other causes of cankers is pruning when the bark is wet or using un-sterilized tools.
The Royal Ann or Royal Anne is a variety of cherry, similar in appearance and taste to the 'Rainier cherry'.
Schisandra chinensis, whose fruit is called magnolia berry or five-flavor fruit, is a vine plant native to forests of Northern China, the Russian Far East and Korea. Wild varieties are also found in Japan. It is hardy in USDA Zone 4. The fruits are red berries in dense clusters around 10 centimetres (3.9 in) long.
Tree paint, also known as wound dressing, is any substance applied to damaged surfaces of a tree intended to improve its health. It is commonly applied after pruning, or at locations where the tree bark has been damaged.
Grafting or graftage is a horticultural technique whereby tissues of plants are joined so as to continue their growth together. The upper part of the combined plant is called the scion while the lower part is called the rootstock. The success of this joining requires that the vascular tissues grow together. The natural equivalent of this process is inosculation. The technique is most commonly used in asexual propagation of commercially grown plants for the horticultural and agricultural trades. The scion is typically joined to the rootstock at the soil line; however, top work grafting may occur far above this line, leaving an understock consisting of the lower part of the trunk and the root system.
In viticulture, the canopy of a grapevine includes the parts of the vine visible aboveground - the trunk, cordon, stems, leaves, flowers, and fruit. The canopy plays a key role in light energy capture via photosynthesis, water use as regulated by transpiration, and microclimate of ripening grapes. Canopy management is an important aspect of viticulture due to its effect on grape yields, quality, vigor, and the prevention of grape diseases. Various viticulture problems, such as uneven grape ripening, sunburn, and frost damage, can be addressed by skillful canopy management. In addition to pruning and leaf trim, the canopy is often trained on trellis systems to guide its growth and assist in access for ongoing management and harvest.
Syzygium floribundum, synonym Waterhousea floribunda, is a rainforest tree of eastern Australia. It grows along streams from the Williams River near Dungog to Mackay in central eastern Queensland. Known as the weeping lilli pilli, this tree is widely planted as an ornamental. Planted trees from 1827 may be seen at the Royal Botanic Gardens, Sydney. However, these trees are damaged and threatened by the roosting grey headed flying foxes. A very large tree is located at Western Park in Auckland, New Zealand.
Frost crack or Southwest canker is a form of tree bark damage sometimes found on thin barked trees, visible as vertical fractures on the southerly facing surfaces of tree trunks. Frost crack is distinct from sun scald and sun crack and physically differs from normal rough-bark characteristics as seen in mature oaks, pines, poplars and other tree species.
Kiggelaria africana is a large, robust, low-branching African tree, and is currently the only accepted species in the genus Kiggelaria.
Leucostoma canker is a fungal disease that can kill stone fruit. The disease is caused by the plant pathogens Leucostoma persoonii and Leucostoma cinctum (teleomorph) and Cytospora leucostoma and Cytospora cincta (anamorphs). The disease can have a variety of signs and symptoms depending on the part of the tree infected. One of the most lethal symptoms of the disease are the Leucostoma cankers. The severity of the Leucostoma cankers is dependent on the part of the plant infected. The fungus infects through injured, dying or dead tissues of the trees. Disease management can consist of cultural management practices such as pruning, late season fertilizers or chemical management through measures such as insect control. Leucostoma canker of stone fruit can cause significant economic losses due to reduced fruit production or disease management practices. It is one of the most important diseases of stone fruit tree all over the world.
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