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Tiny Yellow Spots on Apple Tree Leaves

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Apple trees (Malus domestica) grow in full sun in U.S. Department of Agriculture plant hardiness zones 3 through 9, depending on the cultivar. There are over 100 varieties of apple tree with different heights, fruit characteristics, disease and pest resistance, cold hardiness, chill hours and days to maturity. Problems such as yellow leaf spots can be indicators of disease or insect infestations.

Mites

Mites can cause damage to foliage when they are present in large numbers. Signs of mites include pale dots on the leaves, distorted leaf shape, leaf drop and occasionally visible webbing on the undersides of leaves. Spray with dormant oil in the winter dormant season to kill mite eggs. Monitor the leaves in the summer when the mites are most active. If the infestation is severe, predatory insects such as pirate bugs eat mites. Chemical mite control can also be used if necessary.

Whiteflies

Signs of whitefly infestations include clouds of whiteflies flying up from the leaves when you shake the apple tree, yellow dots on the leaves, and leaves curling then turning brown. If the whiteflies are concentrated in one area, you can remove the infected leaves or branch to remove the pests. Lady bugs, lacewing larvae and parasitic wasps are all natural predators of whiteflies. You can also dislodge the flies with prays of water or treat the apple tree with horticultural oil.

Cedar-Apple Rust

Cedar-apple rust is a fungal disease that cycles back and forth between apple trees and cedar or juniper trees. Both types of tree must be present for the disease to spread. If there are cedars or junipers planted within 2 miles of your apple trees, they may contract the fungus. It appears on apple trees as small yellow spots on the tops of leaves that enlarge and acquire red borders. They are accompanied on the undersides of leaves by hairy, protruding lesions.

Cedar-Apple Rust Control

If possible, remove the cedar or juniper trees in a 2-mile radius around your apple trees. If there are only a few cedars, during the winter dormant season remove all the galls from the cedar trees before the orange tail-like horns form on the galls. Spray apple trees with a rust-controlling fungicide beginning when flower buds turn pink in early spring. Spray every 7 to 10 days until late spring or early summer when the weather is no longer cool and wet and spores aren’t spreading. Consider planting rust-resistant trees such as “Dakota” or “Dayton.”

Tiny Yellow Spots on Apple Tree Leaves. Apple trees (Malus domestica) grow in full sun in U.S. Department of Agriculture plant hardiness zones 3 through 9, depending on the cultivar. There are over 100 varieties of apple tree with different heights, fruit characteristics, disease and pest resistance, cold hardiness, …

Leaf Curl and Yellow Spots on an Apple Tree

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Among the range of mysterious symptoms that strike apple trees are curling leaves, as well as spots on the leaves and fruit. Apples can have more than one problem at a time. So, it’s wise to look for secondary symptoms to determine the presence of such pests as aphids, which are prime suspects in apple leaf-curling, and/or cedar-apple fungus, which first appears as yellow spots on leaves and apples. Because other pests and diseases can cause discolorations and misshapen leaves, make sure you’ve correctly identified the problem before you start treatment.

Cedar-Apple Rust

Yellow spots on both the leaves and the fruits of apple trees are characteristic of cedar-apple rust. Over the course of the growing season, these upper-leaf yellow spots often develop a red border, become larger and spread to the bottom of the leaf. The spots also develop tube-shaped growths that curl back over onto the leaves. The disease gets its name because of its lifespan, which begins as a fungus on cedar and juniper trees before jumping over to apple trees. Damage to apple trees can include spoiled apples, lower yield and decreased fruit size. Untreated cases can eventually cause the trees to stop producing.

Treating Rust

Removing nearby cedars and junipers you think are infected is a good first step to eradicating cedar-apple rust. Look for gall growths on junipers and cedars, sometimes called “cedar apples.” Fungicidal sprays specifically targeted to cedar-apple rust are best applied on apple trees when they begin to blossom. If you plant new apple trees, choose rust-resistant types, such as “Cortland,” “Baldwin,” “Empire,” “Jersey-Mac,” “Red Delicious” and “McIntosh.”

Aphids

In apples, leaf curling is often a sign of an aphid infestation. If the fruits are shaped oddly, rather than spotted — as happens with cedar-apple rust — that may be a sign you have aphids instead of, or along with, cedar-apple rust. Among the most damaging of the aphids that attack apples is the rosy apple aphid, which can also harm the apples themselves. Look for the aphids to determine if leaf curl is caused by the tiny pests, which are dark green in early spring and purple later in the season. The clustering insects gather on the leaves and on the fruit, then begin to lay shiny black eggs on the fruit spurs of the tree.

Aphid Control

You may be able to prevent future infestations by removing nearby weeds, such as plantain, an alternate host for the rosy apple aphid. Avoid insecticidal sprays unless it’s a last resort, because you risk also killing the beneficial insects that keep the aphids in check later in the season. If the aphids are a yearly problem, apply dormant oil spray in late winter, which will smother eggs and larvae.

Leaf Curl and Yellow Spots on an Apple Tree. Among the range of mysterious symptoms that strike apple trees are curling leaves, as well as spots on the leaves and fruit. Apples can have more than one problem at a time. So, it’s wise to look for secondary symptoms to determine the presence of such pests as aphids, …