Problems on apple leaves
Leaf spots/blotches on foliage - In a random or regular pattern are often caused by misapplication or spraying on hot days.
Leaf yellowing or browning
- Drought stress - first observed on newer growth. Leaf tips and margins may appear dry or scorched (brown and dry).
- Excessive water - older leaves uniformly yellow.
Leaf scorching /marginal burning (the edges of the leaves are dry and brown)
- Pesticide burn - including soaps and oils. Stressed plants are more likely to be burned. Emulsifiable concentrates are more likely to burn than wettable powders. Leaf margins are affected first. Leaves are particularly susceptible to burn when temperatures exceed 80-85°F. Copper, sulfur, and Captan® fungicides may cause leaf burn.
- Fertilizer burn/root damage - Marginal leaf scorch and root dieback caused by root contact with excessive salts from fertilizers.
- Drought stress is first seen on new growth.
Leaves curled, twisted, or rolled
- Sub-freezing temperatures after bud swell. First leaves will curl and be off-color.
- Herbicide injury - The new growth is affected first. Do not apply herbicides near fruit trees.
Wilting of foliage
- Drought stress - foliage wilts, droops and drops prematurely. May lead to twig and limb dieback. Provide adequate water during the summer and fall months.
- Root damage - associated with freezes, dry sites, drought, insufficient watering, or mechanical injury. Prune out affected branches. Don’t cultivate near the root zone.
- Poorly drained/heavy clay soils - limits root growth. Select suitable, well-drained planting sites.
Problems on limbs or trunk
- Frost/freeze cracks, sunscald - cracks usually occur on the south or west side of a tree. Caused, in part, by differential freezing and thawing of water in trees. Consider painting the trunks and large scaffold branches of young trees with white latex paint. Failure of trees to properly harden off makes them more vulnerable to frost crack and sunscald injury. Avoid late summer-early fall pruning or fertilizing.
- Trunk bark/wood is gouged or scarred - Lawnmower, string trimmer injury, embedded wires, or collars from tree support apparatus. - Mulch to within 6 inches of trunk. If tree support is necessary due to slope, high wind, or type of dwarfing rootstock, be sure to use a soft collar and adjust annually to allow for tree growth.
- Water sprouts/suckers - Environmental stress. Removal of large branches and limbs causes prolific growth of water sprouts directly below the pruning cut. In all cases promptly pull or cut all suckers and water sprouts at the point of attachment, unless you wish to select one to train as a scaffold branch.
- Dark, raised circles on the trunk with rough texture - Burr knots: caused by the progressive formation of aerial roots. Occurs frequently with dwarfing rootstocks M.7, M.9, M.26, MM.106, MM.111, and Mark. Burr knots can weaken a tree structurally if present in large numbers.
- Top of young tree breaks off at or near ground level - Failure of graft union or incompatibility between scion wood and rootstock. Check with suppliers before purchasing trees to determine the degree of compatibility.
Problems with apple blossoms or fruit
Blooms are brown and dry or water-soaked (blasted)/Bud cross-section reveals brown tissue
- Winter-kill of buds - extended periods of very cold temperatures. Young trees are more vulnerable. Blooms and buds at the ends of branches and facing upwards are more vulnerable. Avoid planting very early blooming cultivars. For further information on buds and killing temperatures.
- Spring frost damage to buds and flowers - open blooms are more cold-sensitive. Cover espaliered or short stature trees with tarps or quilts to prevent freeze damage.
- Low-temperature damage in early spring - trees may leaf out without flowering. Leaf buds are hardier than flower buds. Avoid planting very early blooming cultivars.
- Misuse of dormant oil sprays or pesticide sprays, including spraying when blooms are open or when temperatures are below 40°F. Over-spraying dormant oil, lime-sulfur, and other fungicides and insecticides may damage buds and blooms. Follow label directions.
- Stressful conditions - drought, wind, low temperatures.
- Lack of pollinizer trees - almost all apple and pear cultivars are self-infertile. At least two different cultivars with similar bloom times are required for pollination and fertilization. Determine the pollination requirements of trees before planting. Pollination charts are available in fruit tree catalogs.
- Poor pollination/fertilization - bee activity is low during cool, wet weather.
- Spraying insecticides during bloom period - Avoid broad-spectrum pesticides that kill pollinating insects.
- Over-use of nitrogen fertilizers prior to bloom period. Reduce applications of high nitrogen fertilizers.