How can you tell if your tree is sick? Often, there are some clear signs that something is wrong, such as yellowing or spotted leaves. But sometimes it’s not that obvious until a branch breaks off of the tree starts to lean.
In this article, we cover 8 common signs of a sick tree – symptoms that show your tree is suffering from pests, disease, or environmental stress, including:
- Yellowing leaves
- Brown and dying leaves and needles
- Spots or blemishes on leaves, fruit, and/or bark
- Fuzzy or moldy-looking patches
- Holes in leaves
- Dead, dying or dropping branches
- Leaning tree
Once you know the common signs that something is wrong with your tree, you’ll have a better idea how to deal with the problem.
Sign #1 – Wilting Leaves
If your tree has wilted leaves, pay attention. Leaves are a tree’s farmers, harvesting sunlight and processing it into food energy. But if they’re wilting, they’re not working at their full capacity and the whole tree suffers.
There are many reasons why tree leaves wilt; it may be an easily remedied issue, or it could be a bigger problem that requires treatment.
So, what makes leaves wilt?
Heat stress wilts leaves. Leaves respond to temperature and humidity by regulating how much water they take up from the tree’s root system and release (transpire) from their pores. When the weather gets too hot, leaves can’t take up and release water fast enough, and they wilt.
A schedule of slow, deep watering in the early mornings should solve the problem until temperatures drop.
Trees that are drought-stressed during hot weather, meaning there isn’t enough water in the soil for tree roots to keep the tree hydrated, will also wilt. A regular supplemental irrigation schedule should keep your trees from wilting until rainfall returns. If wilting is caused by drought, your tree’s leaves should be back to normal within a day or two after a good soaking,
If your trees are not stressed by heat or drought, wilting leaves may mean something else. If you have water-logged soil that doesn’t drain well, wilting leaves can be an indication. In this case, it’s lack of oxygen that causes wilting, as too much water is drowning leaf tissue.
How can you tell the difference between tree leaves wilting from heat or drought stress versus those wilting from too much water? While both conditions cause the tips and the edges of leaves to brown and die, heat- and drought-stressed leaves will be browner and drier overall while overwatered leaves will be soft and limp.
Other causes of wilting leaves include diseases, such as fireblight, which appears during warm, rainy spring weather. Fireblight is a bacterial disease that affects plants in the rose family, including apple and pear trees. The infected leaves wilt and look as though they’ve been burned.
One key difference in identifying fireblight is that it first appears early in the growing season, and it affects only the portion of the tree that has been infected. In contrast, the whole tree is affected by heat and water stress.
Note: Unlike temporary dry or hot conditions, fire blight is a potentially fatal disease and needs immediate attention.
Connecticut’s Agricultural Extension Service has more information about identifying and treating fire blight.
Sign #2 – Yellowing Leaves
If your trees have yellow leaves (and it’s not due to fall color), it’s often the result of nutrient deficiency. When your trees aren’t getting the full range of nutrients they need, their leaves tell you by becoming yellow or chlorotic. You may also find stunted leaves and fruit.
Yellowing leaves generally occur because:
- Your soil’s pH is too low(meaning it’s highly acid). This makes soil’s mineral nutrients, such as iron, insoluble and the tree cannot absorb them.
- There aren’t enough soil minerals, or the right minerals, present in the soil.
- Your soil lacks nitrogen, which is the macronutrient most responsible for green growth.
How can you tell which deficiency is which?
- Nitrogen deficiency will show up on old leaves, as the tree sends its limited nitrogen to new, developing leaves.
- Yellowing from iron chlorosis will appear in all leaves, but those leaves will retain green veins.
For both conditions, fertilizing your trees is the best treatment. In most cases, slow-release fertilizers and compost added to the soil will provide the missing nutrients. However, it’s worth noting that extremely acid soils can’t be permanently changed to become more alkaline. In that situation, the best approach is to choose plants that are adapted to acid soil conditions, rather than creating an artificial cycle of fertilizing to keep struggling trees alive in an inhospitable environment.
Sign #3 – Brown & Dying Leaves or Needles
Salt damage from winter road salt or salt spray will show up as brown, dying, and dead leaves and needles. It’s seen mostly in spring and early summer as plants start to leaf out. Thankfully, salt damage can be prevented with a few simple precautions.
If you live near Long Island Sound, wind-borne salt can cause leaf browning and burning. In windy locations, leaves can also dry out (especially in winter). Choosing trees with thick, protected leaves adapted to windy, salty conditions is the best way to minimize wind damage; save more delicate trees for protected areas.
In autumn, you may notice pine needles turning yellow and dropping. While it can look alarming, it’s usually not a cause for concern. Although pines are “evergreen” trees, they normally drop old needles in fall to make space for new growth in spring.
Sign #4 – Spots & Blemishes on Leaves, Fruit, or Bark
Many fungal and bacterial diseases cause spots, blotches, sunken areas, and other blemishes on tree leaves, fruit, and/or bark. Some spots are also signs of insect damage, such as yellow stippling caused by sap-sucking spider mites.
To diagnose the issue, look at the color, shape, size, and location of the spots, as well as the time of year and the tree species. In some cases, you may see insect pests that are causing the problem (although some, such as spider mites, are so small they’re difficult to see with the naked eye). In other situations, there may be other signs that can help you diagnose the issue, such as the presence of fungal fruiting bodies or galls.
In most cases, it’s best to have a Certified Arborist inspect spots or blemishes on your trees. Proper diagnosis is essential to effective treatment; improper diagnosis can lead to ineffective treatment or even damage to the plant or beneficial insects.
Sign #5 – Fuzzy or Moldy Areas on Leaves
Black, white, or gray patches on leaves that look “furry” or powdery are usually signs of a fungal infection. Powdery mildew and black sooty mold are two common examples, although they have very different causes.
Powdery mildew is a fuzzy, whitish coating that appears on the leaves of landscape shrubs, such as lilacs, as well as perennials (phlox are frequently affected), annuals, and vegetables. It usually shows up later in the growing season, particularly during humid weather, on overgrown or closely-spaced plants, and on new growth.
In contrast, black sooty mold is a fungus that grows on the sticky substance (called honeydew) excreted by aphids as they feed on the sap in leaves. It will grow on any surfaces covered by honeydew, including leaves and branches but also anything beneath the tree, such as decks, patio furniture, driveways, roofs, and walls.
There are many other types of fungal infections that commonly affect trees and shrubs in Connecticut. If you’re not sure what it is, it’s best to bring in an arborist to inspect the plant, diagnose the issue, and recommend a treatment or course of action.
Treatment usually involves prevention (such as pruning to increase air circulation throughout a shrub or tree), removing infected debris (don’t compost it!), watering early in the day to allow leaves to dry, and using fungicide applications when needed (most are applied in early spring).
Sign #5 – Holes in Tree Leaves
Holes or ragged areas in leaves can be a problem that requires treatment. But, most often, it’s just temporary cosmetic damage that won’t seriously harm your tree.
If your tree has holes in its leaves, it may be from insect damage. Insects that chew, such as beetles and caterpillars, will move along the undersides of leaves, eating leaf tissue and leaving holes as they go. Usually, this is just temporary cosmetic damage that won’t seriously harm your tree, as beetles will fly off to other trees and caterpillars turn into butterflies after a few weeks.
However, more serious insect infestations need to be treated with sprays or systemic tree injections.
Another cause of holes in tree leaves is fungal diseases. For example, shot hole disease, as the name suggests, creates scatterings of small holes in leaves. Shot hole disease affects fruit trees in the Prunus genera, such as:
- Peaches, and
Fungal leaf diseases are usually spread by wind and splashing water depositing spores on leaves. Just as with spraying for insects, identifying the disease first means you’ll know when and what to spray to effectively combat it.
One way to tell the difference between leaf holes from insect damage and fungal damage is their development:
- fungal leaf diseases will start with a blemish that’s brown or black, often with a ring of yellowing leaf tissue around it, and will turn into a hole as the leaf damage progresses
- insect damage appears quickly, with no signs of blemishes or spots before the holes appear
Leaf damage also occurs because of strong winds. Wind and cold can dry out leaves, and persistent, strong winds can tear thin leaves the way strong winds tatter flags. Wind damage is irregular and can look like several types of damage at once. Look for:
- Ragged, wind-torn leaf edges
- Scorched-looking leaves from drying winds
- Leaves that are stunted or have curled edges from desiccation.
Sign #7 – Dead, Dying, or Dropping Branches
If large branches break or drop, take the time to examine your tree as it might mean there’s a serious tree-health issue developing. While a tree’s size, structure, and appearance change over its lifespan, a healthy tree doesn’t usually drop large branches.
Dead or dying branches can be a sign of natural tree decline—if it’s old. An old tree slows down as it ages and may no longer produce enough food energy to support all its structure. When this happens, a portion of its branches will decline and die. Eventually, their attachment to the tree’s trunk or to larger structural branches weakens, and they drop.
But branch drop can also be a sign of tree disease. When a branch is compromised by disease and decay, the tree will separate the branch from the rest of the tree’s internal system to prevent the spread of disease. With its resources cut off, the branch will be killed by disease and decay and will break off or drop.
A tree in decline usually has:
- No flowering or fruiting
- Areas of twig and branch dieback
- Twigs and branches with sparse foliage or no leaves at all.
If your tree has been healthy and vigorous, this change is reason enough to have an arborist inspect it. Depending on the reason for the branch dieback, an arborist may be able to prune out diseased branches and keep the rest of the tree healthy. It’s better to find out sooner than later, as waiting too long may mean that disease and decay have spread too extensively to save the tree.
If your tree is dropping more than the occasional branch, and if these branches are large, it’s time to examine your tree. And we don’t mean you!
Unless you can see and treat what is wrong with your tree from the ground, call an arborist. Large trees are dangerous. Too many homeowners are injured and killed each year trying to climb them, prune them, or remove dead limbs from them. Let a professional with training, safety gear, equipment, and knowledge examine your tree.
Sign #8 – The Tree is Leaning
If your tree’s trunk is leaning it’s important to find out what’s wrong, fast. While you may not be able to see any reason for its leaning, there may be interior or underground damage that’s causing it. An unstable tree, especially a large one, can be a dangerous hazard and can fall over without warning.
- Oozing wounds or cankers on the tree’s trunk
- Areas of sunken bark
- Insect infestations
- Bark cracks or swollen raised areas of bark
- Sawdust collecting at the base of your tree’s trunk.
All these are signals that your tree is struggling against decay and its anchoring roots or trunk strength have been lost. Mushrooms, or “conks,” growing on your tree’s bark mean that your tree is currently decaying, and these fungi are using the nutrients from the decaying wood to grow.
Call Us for Help with Your Trees
Trees are a valuable resource that can live long, healthy lives – if they’re properly cared for. By regularly inspecting your trees, you can spot any problems early and get them diagnosed and treated before they become a more serious issue.
While we always encourage tree owners to check their trees, we also encourage getting a professional inspection before doing any DIY tree care. We have equipment that allows our experienced arborists to reach the high crowns of large trees and down into the mysterious underground world of tree roots. This lets us accurately inspect and diagnose your whole tree’s health. The right treatment at the right time can make all the difference!
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