Browning apple tree leaves

What Causes Brown Edges on Apple Tree Leaves?

Related Articles

Apple trees can suffer damage to their fruit, branches, trunk and leaves due to disease, insect pests, environmental conditions and nutrient deficiencies. The specific symptom of scorching or browning of the edges on apple tree leaves is associated with drought, salt injury, potassium or magnesium deficiency. Often, more than one condition or deficiency may cause scorched edges on apple tree leaves.

Drought

Drought conditions can turn the tips and edges of apple tree leaves brown and young leaves are especially susceptible. Browning of leaves is worse when the drought is accompanied by drying winds. After the leaf edges have dried and browned, the leaf may completely dry out and drop. Water trees at least once a week during drought conditions and create a windbreak, such as a hedge, to reduce exposure of your apple trees to drying winds.

Salt Injury

Browning or scorching of apple leaf edges may occur due to excessive salt — sodium chloride or calcium chloride — in the soil or water. Salt damage usually affects the older leaves on apple tree shoots with the growing tips of the shoot remaining green. The cause of excessive salt exposure may be due to large amounts of salts in fertilizers, irrigation water, foliar sprays or salt-laden winds in coastal areas. Leaf scorch can also be caused by winter road salt applications near apple trees. Deep watering can reduce salt injury.

Potassium Deficiency

The first signs of potassium deficiency show up in the leaves of apple trees. Older leaves develop brown edges and the leaves may curl up, creating a little boat shape. These symptoms are characteristic on apple trees and occur less often on other fruit trees. Potassium deficiency is caused by either a lack of sufficient potassium, as occurs in infertile soils, or a high soil pH level, indicating alkaline, which prevents the apple tree from taking up potassium and other nutrients. The optimal pH for nutrient uptake by apple trees is slightly acidic, a pH level of 6.5 to 7. Excess nitrogen fertilization also increases potassium deficiency. If you suspect a potassium deficiency, perform a leaf and soil analysis using a home test kit or use a laboratory service before beginning treatment or adding potassium fertilizer.

Magnesium Deficiency

Magnesium deficiency is a less common cause of scorching or browning of the edges of apple tree leaves. Discoloration starts out yellow at the edges and around rhe major veins of the older basal leaves. Symptoms first appear in mid to late summer and excessive potassium fertilizer applications increase symptoms. Magnesium deficiency is often associated with sandy soils. Analysis of soil pH and mineral content of soil and apple tree leaves will determine if the apple tree suffers from magnesium deficiency.

Источник

Why Apple Tree Leaves Turn Brown (and How To Fix It)

It’s fairly common for apple tree leaves to turn brown, but it can have many possible causes. Some sources say one thing, while others say another. So, I wanted to dig a little deeper and find out the most likely reasons why apple tree leaves turn brown. Here’s what I found.

Apple tree leaves usually turn brown from improper watering, weather stress, or a disease called fire blight. The easiest way to tell what’s causing the brown leaves is to check if they’re curled or look scorched. If they’re just curled, the tree needs water. If they’re scorched looking, it’s likely fire blight.

So, while there are several reasons why apple tree leaves turn brown, how can you tell what’s causing it, and how can it be fixed?

By the way, if you’d like some gardening supplies that are on sale this fall and winter, check out these new items on Amazon.

Over or Under-Watering

If your apple tree has brown leaves, watering should be the first thing you check.

Over and under-watering apple trees are common reasons why they get brown leaves. Compared to other causes, watering is also the easiest to test. To prevent leaves from turning brown, only water the tree when the first 2-4 inches of soil gets dry and use mulch and compost.

Overwatering

Symptoms of overwatering an apple tree include:

Overwatering can be caused by many factors but is the most common in clay soils or those with poor drainage.

Clay soils have tightly packed particles, preventing the soil from draining well. This can lead apple trees to hold water for days at a time, leading to other issues, such as root rot (a fungal disease that typically requires repotting the tree).

The most common reasons why apple trees get overwatered are:

• Watering too frequently
• Clay soil
• Poor drainage
• Watering during rainstorms

To prevent overwatering apple trees, use loamy, well-draining soil and only water when the top 2-4 inches of soil gets dry. By using compost and mulch, you can water apple trees every 1-2 weeks. The compost will help hold the moisture and the mulch prevents evaporation.

If you check your apple tree’s soil 2 or more hours after watering it, and it’s still sopping wet, it likely has poor drainage and is getting overwatered.

You can test your soil’s drainage by digging a 1-foot by 1-foot hole near the apple tree and filling it with water. If the water is still present 2 hours after, the soil needs to be amended with better drainage. Compost, sand, and perlite are some good amendments to use. Over time, these materials will work their way into the soil and promote aeration.

While overwatering apple trees can lead to brown leaves, it’s more likely to lead to green leaves being shed. Under-watering (drought-stress) is a far more likely cause of brown leaves on apple trees.

Under-Watering

Compared to overwatering, a lack of water dries out the apple tree’s leaves—which curl to conserve moisture, and if not watered soon, will turn brown and die.

Under-watering apple trees is easy to do, and it can result in several symptoms. Most commonly, the apple tree’s leaves will begin curling, but brown leaves can occur if the drought stress is bad enough.

The common symptoms of under-watering apple trees include:

You can tell if your apple tree is under-watered if the soil is bone dry. Typically, this happens in hotter weather. For this reason, composting and mulching your apple trees are essential.

Composting not only helps the soil receive valuable nutrients but also improves the richness of the soil. This is important because each 1% increase in a soil’s organic matter can help hold 20,000 gallons more water per acre. And who doesn’t want to use less water?

Similarly, mulching greatly improves the water retention of the soil by limiting evaporation. Mulch also shields the soil from baking in the hot sun, which helps protect the tree’s roots as well as the beneficial bacteria in the soil. Some good mulches for apple trees include straw, bark, pine needles, and leaves.

Overall, mulching and composting are two of the most valuable practices you can do in your garden and can dramatically help with under-watering and drought stress.

Weather Stress

Apple trees can develop brown leaves from environmental stress, such as extreme weather. Generally, apple trees prefer USDA growing zones 3-9 and climates with cold winters, moderate summers, and medium-high humidity. However, apple trees are fairly flexible and can tolerate temperatures ranging from -40ºF to 100ºF.

If your local temperatures have recently been outside of these suggested growing zones, it’s a likely cause of the brown leaves on your apple tree.

In hot weather, you can help cool apple trees by providing a couple hours of afternoon shade and mulching their soil. Make sure the soil stays moist as apple trees primarily stay cool by sending moisture from the roots to the leaves.

Cold weather is less likely to stress apple trees since they’re naturally cold-hardy. If your weather does get too cold for your apple tree variety, then consider growing it indoors or in a greenhouse.

While too much hot or cold exposure can be bad, like most living things, apple trees can benefit from some stress (also called hormetic, or mild stress). An example of this would be the chill hours that apple trees benefit from. Apple trees typically benefit from 400-1000 hours of chill hours per year at 45ºF or less, depending on the variety of trees. These chill hours will help stimulate the tree to provide more leaves and flowers.

So, try your best to keep your apple trees within the -40ºF to 100ºF range. If you get a mild to moderate frost every year, you shouldn’t need to worry as this should help your apple trees bloom during the growing season. Just make sure to check the growing zone of your specific variety of apple trees.

Improper Nutrients

A lack or excess of nutrients is not too likely to cause brown leaves on apple trees, but it shouldn’t be ruled out. Improper nutrients can cause several growing issues, such as leaf drop, fruit drop, and browning leaves. Apple trees should be fed a fertilizer once per growing season or compost every 1-2 months.

Generally, apple trees should be fertilized with either a balanced NPK (nitrogen, phosphorus, and potassium) or one with higher nitrogen. For example, a fertilizer with a 6-2-4 NPK would work well for most apple trees, while apple trees suffering from fire blight should be fed a more balanced fertilizer (such as a 10-10-10). This is because the higher amount of nitrogen can feed the fire blight bacteria (more on this later).

If your apple tree doesn’t have fire blight, and you’re looking for a good fertilizer to use, Down to Earth’s Organic Fruit Tree Mix on Amazon is a good choice (I use them for my citrus trees).

On the other hand, a simple, quality compost can often be the best thing for apple trees. If you’d like to learn more about making your own homemade fertilizer for your apple trees, make sure to check out my recent post: Create an Amazing Homemade Fertilizer for Your Fruit Trees.

Keep in mind that soil pH is equally important as soil that’s too acidic or alkaline will prevent the tree from absorbing nutrients. Apple trees prefer a soil pH of 6.0-7.0, so keep it in this range if possible (see the image below for a pH scale).

You can measure soil pH by either pH strips or a pH meter. To see which pH meter I use on my plants, you can visit my recommended tools page.

Fire Blight

While a few apple tree diseases can cause brown leaves, fire blight is by far the most common.

Fire blight (erwinia amylovora) is a highly infectious bacterial disease that affects members of the rose family—including apple, pear, crabapple, rose, cotoneaster, mountain ash, hawthorn, quince, spirea, and pyracantha. Fire blight causes browning and disfiguring of the leaves and fruit, sometimes killing the tree.

Fire blight is one of the biggest reasons why apple trees get brown leaves. An easy way to tell if your apple tree has fire blight is if the branches have a 180º bend and a scorched appearance (hence its name).

It can be difficult to treat fire blight, but there are both conventional and organic methods that help control it. Mostly, treating fire blight involves pruning the diseased branches and applying a spray while the tree is dormant, as well as blooming.

For more information about fire blight and how to treat it, refer to my recent post: Fire Blight: The Most Effective and Natural Treatments.

Fire Blight Resistant Apple Trees

It can be helpful to know if your apple trees are resistant to fire blight or not. While no apple tree is immune to fire blight, having a tree with genetic resistance can make this disease much more manageable. Here’s a ranked list that I put together of apple trees that are resistant and susceptible to fire blight.

Most Resistant	Moderately Resistant	Least Resistant
Haralson	Honeycrisp	Cortland
Liberty	Zestar	Keepsake
Red Baron	–	McIntosh
SnowSweet	–	State Fair
Chestnut crab	–	Sweet Sixteen
Dolgo crab	–	Beacon
–	–	Fireside
–	–	Honeygold
–	–	Paulared
–	–	Wealthy

For more information about fire-blight-resistant trees, check out this resource from the University of Minnesota. Also, this page is a good resource for other diseases that can cause brown leaves on apple trees.

Final Thoughts

A good rule to keep in mind that if your apple tree leaves are curling and then browning, the tree is likely under-watered (or drought-stressed). On the other hand, if its leaves are scorched looking and bent 180º, fire blight is a good possibility. Another way to tell is that trees infected with fire blight typically don’t shed their brown leaves.

While the above causes aren’t exhaustive, I did want to cover the most likely reasons why apple trees get brown leaves and what you can do to resolve it.

If you get stuck, or you believe your apple tree is suffering from a different issue, such as early leaf drop, then a good option would be to check with your county extension office or local professional orchard.

They should be more familiar with why apple tree leaves commonly brown in your region and can likely provide a more specific solution. Your county extension office should also be able to test the nutrients in your apple tree’s soil to see if it’s lacking or has too much of anything.

Источник