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Diagnosing Apple Tree Leaf Discoloration

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Discoloration can be alarming on your apple tree leaves and with good reason. There are a few common causes behind this problem and we have some management tips to help you combat the problem.

Sections

Fireblight

Erwinia amylovora

Distinctive “shepherd’s crook on apple (Penn State Department of Plant Pathology & Environmental Microbiology Archives, Penn State University, Bugwood.org)

Symptoms

Young shoots wilt and droop, forming a distinctive “shepherd’s crook.”
Leaves on infected shoots turn brown as if scorched by fire.
Fruit may turn dark and shriveled and persist on the branch.
Slightly sunken bark cankers may appear on branches and stems.

Fruit on a branch darkened and shriveled by fireblight

Fireblight symptom on fruit (Bruce Watt, University of Maine, Bugwood.org)

Management and other important facts

Plant less susceptible apple and crabapple cultivars.
Mark infected twigs with ribbon or paint during the growing season.
Prune all marked twigs and cankered branches in late winter at least 8-12 inches below the infection.
May also use “ugly stub” method of pruning.
Avoid excessive application of fertilizer that may promote overly lush growth.
If fireblight is a yearly problem on a high value apple tree, apply a copper spray just as the leaf buds are starting to swell in spring; do not apply after ½-inch of green, leafy tissue is visible because the copper spray may burn the leaf tissue

Authors: Esther McGinnis and Kasia Kinzer

Honeycrisp Leaf Mottling

Leaf showing irregular yellow blotches on leaf margins of honecrisp leaf mottling

Note the irregular yellow botches that may be more pronounced in the leaf margins (Esther McGinnis, 线上赌博app)

Symptoms

Leaves have a blotchy pattern of yellowing during the summer
This disorder only appears in young ‘Honeycrisp’ apple trees that are not producing much fruit yet
The appearance is more random than iron chlorosis

Leaf mottling has an irregular pattern and may resemble leafhopper damage (Esther McGinnis, 线上赌博app)

Management and other important facts

This disorder is genetic and occurs primarily in juvenile ‘Honeycrisp’ apple trees
The mottling is caused by the accumulation of large starch granules in the leaves that reduce photosynthesis
No treatment is necessary and the symptoms will abate as the tree matures and produces more apples

Author: Esther McGinnis

Iron Deficiency

Hosts

Freeman maples, silver maple, river birch, Swedish columnar aspen

River birch leaf with interveinal chlorosis (Esther McGinnis, 线上赌博app)

Symptoms

Leaves turn yellow-green or bright yellow but veins remain green (interveinal chlorosis)
In severe cases, leaf margins may turn brown and appear scorched
Symptoms first appear on newest leaves at branch tips
Over time, twigs and branches may die back from the crown
Eventually, the tree may die if the iron deficiency persists for years

Silver maple tree with some dead branches caused by iron deficiency

Branch dieback on silver maple (Joseph Zeleznik, 线上赌博app Extension)

Management and other important facts

This abiotic disorder is caused by an iron deficiency that is associated with alkaline soils, cool temperatures, and wet soils; these conditions render the normally abundant iron in North Dakota soils as unusable by the plant
Foliar sprays of chelated iron may provide quick green-up of the foliage but this treatment is temporary and trees do not always respond
Iron chelate products may be applied to the soil or injected into trees for longer lasting relief
Broadcasting soil acidifiers such as elemental sulfur or iron sulfate onto the soil surface may lower the soil pH; gradually converting the iron in the soil into a usable form by the plant
Replace iron-deficient trees with individuals that are better adapted to alkaline soils

Authors: Esther McGinnis and Kasia Kinzer

Leaf Scorch

Symptoms

Look for browning around the margins of the leaves.
Eventually the entire leaf may turn brown and wilt.
Damage will be worst on branch ends.

Elm tree leaf with brown and crisp edges caused by leaf scorch

Leaf scorch on an elm leaf; symptoms would be similar on apple leaves (Esther McGinnis, 线上赌博app)

Management and other important facts

Leaf scorch is caused by drought or the interruption in the flow of water to the branches and leaves.
Supplemental irrigation may ameliorate the effects of drought.

Author: Esther McGinnis

线上赌博app

Diagnosing Apple Tree Leaf Discoloration

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