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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
Tree cankers that ooze orange or amber-colored sap may indicate that the tree has Cytospora canker disease. The only way of fixing tree cankers caused by the disease is to prune out diseased branches. The best method of control is preventing damage that allows the airborne fungus to gain entry into the tree. Keep reading to learn more about what causes amber sap on trees and what can be done for a tree weeping amber color sap. What is Cytospora Canker? Cytospora cankers occur when the airborne cytospora fungus enters a tree through injuries and damage.
It forms a sunken canker that spreads gradually, eventually girdling the branch and killing everything beyond the site of the canker. The diseased area may become covered with a growth of black fungus. What Causes Amber Sap on Trees? Cytospora canker is caused by the fungus Cytospora chrysosperma. The fungus enters the tree through damaged bark. The types of damage that leave the tree susceptible to infection include pruning wounds, flying debris from lawn mowers, string trimmer injuries, frost, fire and cat scratches. Tiny, bumpy fruiting bodies, called pycnidia, form on the dead tissue, giving the bark a rough texture. The pycnidia ooze an orange or amber, jelly-like sap that stains and discolors the bark. Symptoms are seen on a variety of fruit and shade trees throughout the United States.
How to Control Cankers There is no cure for cytospora canker on fruit trees and shade trees, but you can control the spread of the disease by pruning out the infected area. In late winter or early spring, remove infected branches at least 4 inches below the canker where the tree is weeping amber color sap. Disinfect pruners between cuts with a disinfectant spray or ten percent bleach solution.
If you use bleach on your pruners wash, rinse and dry them before putting them away to prevent corrosion. Proper tree maintenance that prevents stress goes a long way toward helping a tree resist disease and recover from cytospora canker. Water the tree slowly and deeply during dry periods. Fertilize annually in late winter or spring with a low-nitrogen, high-potassium fertilizer. Prune regularly so that you don’t have to make severe cuts later on. Remove dead, damaged and weak twigs and branches that may provide an entry point for disease and never leave stubs attached to trunks or large branches. Remember to disinfect your pruners. Avoid injuring trees when performing lawn maintenance. Raise the mower blades high enough so that they won’t nick exposed roots, and mow so that debris flies away from the tree rather than toward it. Use string trimmers with care to prevent cuts in the bark of the tree.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
If you’ve noticed an outbreak of leaf mottling along with blistering or leaf curl in the garden, then you may have plants affected by TMV. Tobacco mosaic damage is caused by a virus and is prevalent in a variety of plants. So exactly what is tobacco mosaic virus? Keep reading to find out more, as well as how to treat tobacco mosaic virus once it’s found. What is Tobacco Mosaic Virus? Although tobacco mosaic virus (TMV) is named for the first plant in which it was discovered (tobacco) back in the 1800s, it infects over 150 different types of plants.
Among plants affected by TMV are vegetables, weeds and flowers. Tomato, pepper and many ornamental plants are struck annually with TMV. The virus does not produce spores but spreads mechanically, entering plants via wounds. History of Tobacco Mosaic Two scientists made the discovery of the first virus, the Tobacco Mosaic Virus, in the late 1800’s. Although it was known to be a damaging infectious disease, tobacco mosaic was not identified as a virus until 1930. Tobacco Mosaic Damage Tobacco mosaic virus does not usually kill the plant that is infected; it does cause damage to flowers, leaves and fruit and stunts a plant’s growth, however. With tobacco mosaic damage, leaves may appear mottled with dark green and yellow-blistered areas. The virus also causes leaves to curl. Symptoms tend to vary in severity and type depending on the light conditions, moisture, nutrients and temperature. Touching the infected plant and handling a healthy plant that may have a tear or nick, whereby the virus can enter, will spread the virus.
Pollen from an infected plant can also spread the virus, and seeds from a diseased plant can bring the virus to a new area. Insects that chew on plant parts may carry the disease as well. How to Treat Tobacco Mosaic Disease There has not yet been found a chemical treatment that effectively protects plants from TMV. In fact, the virus has been known to survive for up to 50 years in dried plant parts. The best control of the virus is prevention. Reducing and eliminating sources of the virus and the spread of insects can keep the virus kept under control. Sanitation is the key to success.
Garden tools should be kept sterilized. Any small plants that appear to have the virus should be removed immediately from the garden. All plant debris, dead and diseased, should be removed as well to prevent the spread of the disease. In addition, it is always best to avoid smoking while working in the garden, as tobacco products can be infected and this can spread from gardener’s hands to plants. Crop rotation is also an effective way to protect plants from TMV. Virus-free plants should be purchased to help avoid bringing the disease into the garden.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
Leaves that curl, wilt, discolor and die may mean that a plant is suffering from verticillium wilt. You may first notice these symptoms in spring or fall when temperatures are mild. Read on to find out how to distinguish verticillium wilt from other plant diseases and what to do about it. What is Verticillium Wilt? Verticillium wilt is a fungal disease that lives in the soil. It invades susceptible plants through their roots and spreads through the plant’s vascular system. The list of plants affected by verticillium wilt is extensive and includes trees, shrubs, and garden annuals and perennials. It can also affect fruit and vegetable crops. Verticillium wilt symptoms mimic those of other plant diseases and environmental problems, and this makes it hard to diagnose.
The leaves wilt and curl, and turn yellow or red. They eventually turn brown and drop off. Stems and branches die back. It’s not unusual to see these symptoms on one side of the plant while the other side appears unaffected. As the disease travels up a tree or shrub’s vascular system, it leaves dark discolorations. If you peel back the bark, you’ll see dark streaks on the wood. If you cut through a branch and look at the cross section, you’ll see rings of dark color. These discolorations in the wood can help you tell the difference between verticillium wilt and other plant diseases. Control of Verticillium Wilt Verticillium wilt can’t be cured once it enters the plant. It’s best to remove and destroy small, easily replaced plants. The disease remains in the soil after you remove the plant, so don’t plant another susceptible species in the same area.
Verticillium wilt treatment for trees and shrubs focuses on giving the plant the best possible care to build up its resistance. Water the plant regularly, and when possible, provide afternoon shade. Fertilize on schedule, using a low-nitrogen, high-phosphorus fertilizer. Prune off dead and dying branches. You can often get rid of the verticillium wilt fungus in the soil by solarization. Soil solarization heats up the top 6 inches or so of soil to temperatures high enough to kill the fungus. Prepare the soil by tilling or digging and then wetting it down. Cover the area with a clear plastic tarp and bury the edges under a few inches of soil to hold it in place and keep the heat in.
It takes three to five weeks of bright sunlight and warm temperatures for the soil to heat up enough to kill the fungus. Verticillium wilt is a devastating and incurable disease, but with special care and attention, you can preserve the plant and enjoy it for several more years.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
Alternaria leaf spot in the garden is a real problem for growers of brassicas, but it also makes life miserable for tomato and potato growers, causing plaque-like spots on leaves and fruits. Treating alternaria can be difficult, so many gardeners do what they can to prevent this fungus from getting a toe-hold in their plots. Let’s learn more on what is alternaria and how to treat this gardener’s nightmare. What is Alternaria? The fungal pathogens in the genus Alternaria can be devastating to plants year after year.
The spores overwinter on old plant debris and attach themselves to seeds, making alternaria leaf spot especially tricky to completely eliminate if you save your own seeds. Garden vegetables are common targets of these wind-blown spores, but alternaria is not discriminatory in the plants it attacks — apples, citrus, ornamentals and weeds have been known to develop leaf spots caused by this fungus. Alternaria symptoms once infection begins include small, dark, circular spots that regularly reach ½ inch in diameter. As they spread, alternaria leaf spots may change in color from black to tan or gray, with a yellow halo around the outside. Because spot development is heavily influenced by the environment, there are frequently noticeable concentric rings that spread from the initial point of infection. Sporulation causes these spots to develop a fuzzy texture. Some plants tolerate alternaria spots better than others, but as these spots increase on tissues, leaves may wilt or drop, leading to sunburned crops or weak plants. Fruits and vegetable surfaces can be infected with alternaria spots as well, the lesions making them unsightly and unmarketable.
Because alternaria can invade tissues invisibly, eating spot-covered produce is not recommended. How to Treat Alternaria Treatment for alternaria requires fungicide to be sprayed directly on infected plants, as well as improvements in sanitation and crop rotation to prevent future outbreaks. Organic gardeners are limited to sprays of captan or copper fungicides, making control much more challenging. Conventional gardeners can use chlorothanil, fludioxinil, imazalil, iprodine, maneb, mancozeb or thiram on plants listed on the label of their chemical of choice, but should still strive for prevention in areas with known alternaria pathogens. Mulch can help to slow the spread of alternaria spores already in the soil when applied immediately after planting. Experiments at the New York State Agricultural Experiment Station showed that mulched kale crops experienced fewer and less severe problems with alternaria leaf spot than the control plants, with straw mulches significantly more successful at suppression than black plastic or biodegradable plastic mulches. The straw-mulched plants also grew much taller than other plants in the experiment.
Crop rotation is vital to preventing alternaria fungal spores from germinating – although the many alternaria fungal diseases look similar, the fungi themselves are often very specialized in the type of plant they will attack; gardens on four year rotations can avoid alternaria building in the soil. Cleaning up fallen leaves and spent plants as soon as possible will also limit the number of spores in the soil. Healthy, well-spaced plants tend to suffer less severe damage from alternaria than their overly-stressed kin.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
It’s a gardener’s worst nightmare — a young tree, lovingly established and bathed with affection refuses to come into its own, instead collapsing several years after planting. The tree didn’t have problems with insects or any visible diseases, it just faded away. The culprit in cases like this is often phytophthora, a soil-borne pathogen that infects trees, woody plants and even vegetables.
What is Phytophthora? Once known as phytophthora fungus, this organism is now classified as an oomycete, a life form similar to fungus but more closely related to algae. Although perhaps an insignificant distinction when your plants are ill, this new understanding may allow for better control methods in the near future. There are many phytophthora species, some that favor warmer weather and others cooler, but the majority of these oomycetes appear in the spring and fall. Phytophthora symptoms are often generalized, causing weakness and slow collapse in affected plants. Early warning signs are few; most plants appear drought stressed regardless of adequate watering. Some plants wilt and die from water stress during the first warm weather after infection, but others linger for several years before succumbing.
Leaves may appear dull or fade to yellow, red or purple long before fall sets in. Controlling Phytophthora Root Rot A tree demonstrating phytophthora symptoms can sometimes be saved by removing the soil from around the base of the tree all the way down to the top of the main roots, cutting away any bark that’s oozy or dark and leaving the root system exposed. This allows the root system to dry completely, slowing the spread of phytophthora. In most other cases, phytophthora management is limited to prevention. Trees and shrubs, like azaleas, should be planted in well-draining areas, so their roots remain dry for most of the day. Phytophthora only needs four hours of standing water to germinate, making it difficult to combat in areas with poor drainage. Some gardeners get around this by planting their landscaping on mounds 8 to 10 inches tall and being extra careful to plant crowns at the same depth they were at the nursery (often indicated by a dark line on the trunk).
Well-established trees are less frequently affected than younger trees because they have widely spread roots that provide lots of avenues for water and nutrition. If a few sections are damaged, they are prepared to compensate. In smaller plants, such as shrubs or vegetables, all bets are off — they can be lost to phytophthora before you even realize the disease has taken hold.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
No matter how closely you listen to your plants, you’ll never hear a single “Achoo!” from the garden, even if they’re infected with viruses or bacteria. Although plants express these infections differently from humans, some gardeners worry about plant disease transmission to humans — after all, we can get viruses and bacteria, too, right? Can Plant Bacteria Infect a Human? Although it would seem like a no brainer to assume that plant and human diseases are distinct and cannot crossover from plant to gardener, this isn’t the case at all. Human infection from plants is very rare, but it does happen. The primary pathogen of concern is a bacteria known as Pseudomonas aeruginosa, which causes a type of soft rot in plants.
P. aeruginosa infections in humans can invade nearly any tissue in the human body, provided they are already weakened. Symptoms vary widely, from urinary tract infections to dermatitis, gastrointestinal infections and even systemic illness. To make matters worse, this bacterium is becoming increasingly antibiotic resistant in institutional settings. But wait! Before you run to the garden with a can of Lysol, be aware that even in severely ill, hospitalized patients, the infection rate of P. aeruginosa is only 0.4 percent, making it highly unlikely that you will ever develop an infection even if you have open wounds that come in contact with infected plant tissues. Normally-functioning human immune systems make human infection from plants highly improbable.
Do Plant Viruses Make People Sick? Unlike bacteria that can function in a more opportunistic fashion, viruses need very exacting conditions to spread. Even if you eat fruits from your squash mosaic infected melons, you won’t contract the virus responsible for this disease (Note: eating fruits from virus-infected plants isn’t recommended — they’re not usually very tasty but won’t hurt you.). You should always cull virus-infected plants as soon as you realize they’re present in your garden, since they are often vectored from sick plants to healthy ones by sap-sucking insects. Now you can dive in, pruners blazin’, confident that there’s not a significant connection between plant diseases and humans.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
It’s the greatest feeling in the world when your landscape is complete, the trees are big enough to cast a puddle of shade onto the lawn and you can finally relax after the years you’ve spent turning an old drab lawn into a planted paradise. When you notice that sad little plant in the corner, wilted and covered in dark spots, you’ll know it’s time to get back to work if you know how to recognize botryosphaeria canker on plants.
What is Botryosphaeria Canker? Botryosphaeria canker is a common fungal disease of trees and woody shrubs, but it only attacks plants that are already stressed or weakened by other pathogens. Cankering can become quite extensive within the cambian layers, heartwood and inner bark of woody plants, cutting off the tissues that transport water and nutrients throughout the plant. Affected tissues develop black, pimple-like fruiting structures or cankers on bark surfaces. When the bark is peeled back, the wood underneath will be reddish-brown to brown instead of a healthy white to pale green. Some trees will weep gummy sap or develop blisters on their bark along with the more obvious widespread wilting of botryosphaeria canker disease.
Control of Botryosphaeria Canker If caught early, localized botryosphaeria canker on plants can be cut out and the entire plant saved. In the winter or very early spring before bud break, prune any branches or canes back to unaffected tissues and immediately dispose of infected debris. Prevent spreading the botryosphaeria fungus further by soaking pruning tools in a mixture of one part bleach to nine parts water for at least 10 minutes between cuts. Fungicides aren’t generally recommended for botryosphaeria canker treatment, since the fungus penetrates tissues, where chemicals can’t reach. Instead, after pruning out diseased areas of the canopy, pay closer attention to the plant. Make sure that it is properly watered, fertilized and protect it from bark damage.
Once your plant is again thriving, you can keep it from developing new problems with botryosphaeria canker disease by continuing to provide it with excellent care and waiting to prune until late winter or early spring, when it’s still too cold for fungal spores to take hold while the wounds are healing.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
It can be difficult to differentiate between leaf-related problems that occur in the summer garden, but angular leaf spot disease is pretty distinctive, making it easy for new gardeners to diagnose successfully. Plants that develop very regular leaf spots that follow veins may be suffering from this disease. Read on to find out more. What is Angular Leaf Spot? Angular leaf spot in plants is caused by several bacteria that survive in seeds and plant debris, including Pseudomonas syringae and Xanthomonas fragariae. These bacteria are somewhat host-specific, with P.
syringae targeting cucurbits and X. fragariae attacking strawberries. Symptoms first appear as small, water-soaked spots on leaves, but spread rapidly when conditions are moist and ambient temperatures are between 75 and 82 F. (24-28 C.). Spots expand until they fill the entire area between leaf veins, but do not cross over, which creates a tiled appearance on larger leaves. Older spots may dry out and tear, leaving holes behind. On fruits, angular leaf spot disease manifests as perfectly circular, water-soaked spots, much smaller than those on the leaves. As the disease progresses, the spots take on a chalky white appearance and may crack open, allowing pathogens to contaminate fruits and cause fruit rot.
How to Treat Angular Leaf Spot Treating angular leaf spot is not a simple, straightforward task. Once a plant is infected, it cannot be cured easily and most gardeners will remove the plant from their garden to prevent further spreading of the disease. Future problems can be prevented by only using certified, disease-free seed, practicing a three-year crop rotation with different plant families and making a habit out of cleaning up plant debris as it falls to the ground.
Beds with poor drainage or that are over-watered favor angular leaf spot — pay close attention to your watering habits if this disease has already developed in your plants. Before watering, check the soil moisture level with your hand. Unless the top 1 to 2 inches of soil feel dry to the touch, do not water; and when you do, make sure to water at the base of plants. Good watering practices can reduce the risk of many diseases, including angular leaf spots in plants.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
You can tell a lot about your plant’s health from its leaves. When they’re green, shiny and flexible, all systems are go; that plant is happy and care-free. But when plants develop brown leaves in the middle of their canopy or leaf browning in center of leaves, problems are afoot. Most of the time, these symptoms can be traced back to improper growing conditions, but they may also be caused by fungi and viruses.
Causes for Plants Going Brown in Center Crown and Root Rot The center rotting out of a plant is almost always related to crown or root rot. Most plants can’t tolerate a soggy environment, especially those with crowns densely covered with leaves, like African violets. When you keep the soil wet all the time, fungal pathogens take advantage of the humidity that develops under the leaves of these low-growing plants, reproducing rapidly. Both root and crown rot can appear similar in these short plants, with the plants going brown in the center as the disease progresses. If you’re asking yourself, “What is causing brown leaves in center of my plant,” you need to check the soil moisture first. Allow the top inch or two of soil to dry between waterings and never leave plants soaking in water-filled saucers. Plants with root rot may be saved if you catch it in an early stage. Dig your plant, trim out any brown, black or soggy roots and replant into a well-draining medium — chemicals won’t help, the only thing that will fix root rot is a drier environment.
Diseases That Cause Brown Leaves Other reasons why leaves turn brown in middle include fungal diseases like anthracnose and host-specific rusts. They often start along the mid-vein of leaves, either near the center or toward the stem end. Fungal diseases are aggravated or initiated by humid conditions. Rusts can be treated early in the disease process, but good sanitation is vital to prevent it from spreading further. When tiny, rust-colored spots appear in the middle of your plant’s leaves, try neem oil before breaking out stronger chemicals like thiophanate methyl, myclobutanil or chlorothalonil. Remove any plants that resist treatment and keep all plant debris cleaned up off of the ground. Anthracnose also begins along the mid-vein in many plants, but is primarily a problem for woody plants, although tomatoes and other crops have been known to contract it. This fungus creates water-soaked lesions on leaves along the mid-vein that soon dry out and brown. Anthracnose is difficult to treat, but crop rotation and sanitation are the keys to preventing reinfection. A number of plant viruses result in vein necrosis, the death of the central leaf vein and those tissues surrounding it, causing browning. Other common symptoms include discolored spots, rings or bullseyes in a range of colors, general unthriftiness and distortion of emerging growth.
A plant affected by a virus cannot be cured, so it’s best to destroy them before other plants are infected as well. Many viruses are vectored by small, sap-sucking insects; be on the lookout for pests in and around sick plants.
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Dummer. ゛☀
2017年08月08日
Dummer. ゛☀
As gardeners, we face a lot of hurdles when it comes to keeping our plants alive and healthy. If the soil’s wrong, the pH is off, there are too many bugs (or not enough bugs), or disease sets in, we’ve got to know what to do and do it right away. Bacterial or fungal diseases can be devastating, but they usually give us a fighting chance. Viroids and viruses are another story altogether. Impatiens necrotic spot virus (INSV) is one of the most common viruses in the plant world. It’s an intimidating diagnosis for your plants, but without understanding the disease, you’ll never be able to manage it properly. What is INSV? INSV is an aggressive plant virus that can quickly infect greenhouses and gardens, and is especially common in impatiens plants.
It results in total losses, since plants affected by impatiens necrotic spot virus are no longer marketable, cannot be used for seed-saving and can continue to spread the virus as long as they’re present. Impatiens necrotic spot virus symptoms are highly variable, a fact that often delays gardeners’ decision making about infected plants. They may develop yellow bull’s eye markings, stem lesions, black ring spots and other leaf lesions, or infected plants may simply struggle to thrive. Once you suspect impatiens necrotic spot, treatment won’t help – you must destroy the plant immediately. If many plants are infected, it’s a good idea to contact your university extension office for testing to confirm the virus is present.
What Causes Impatiens Necrotic Spot? Western flower thrips are the primary vector for INSV in the garden and greenhouse. These tiny insects spend most of their lives on or near the flowers of your plants, though you may never see them directly. If you’ve noticed black spots or areas where pollen is spread across the flower, western flower thrips may be to blame. Placing yellow or blue sticky cards throughout potentially infected areas are the best way to confirm your suspicions of an infestation. Having flower thrips is annoying, but if none of your plants are infected with INSV, they can’t transmit the disease on their own. This is why it’s so important to quarantine any new plants that come into close contact with your old plants.
You should also clean your tools thoroughly between plants, especially if you are concerned about INSV. It can easily be transmitted via plant fluids, like those found in the stems and branches. Unfortunately, there’s no easy answer for INSV. Practicing good tool hygiene, keeping thrips under control and removing suspect plants are the best ways to protect yourself from the heartbreak this disease brings with it.
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