Foliage or leaves
Leaf scorching/ marginal burning
- Pesticide burn - including soaps and oils. Stressed plants are more likely to be burned and emulsifiable concentrates (liquid concentrates) are more likely to burn than wettable powders (finely ground powder). 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 - causes marginal leaf scorch and possible root dieback. Follow U of MD recommendations.
- Damage from lawn herbicides - marginal scorching. Read the product label before applying.
- Drought stress - marginal scorching. It is important to irrigate during dry periods.
- Sunburn - yellow, brown, or white areas develop on the upper sides of leaves. Damage can occur due to excessive sunlight, heat, and insufficient water.
Branches and Trunk
- Gum oozes from holes at the base of the trunk or lower branch crotches (sawdust-like frass may be observed - If the gum is clear suspect mechanical injury or stress. If the gum is mixed with sawdust-like frass (borer excrement) suspect borers. Found primarily on peach and nectarine but will also attack cherry. One or two borers can kill a tree.
- Root damage, drought, or mechanical injury - prune out affected areas and keep trees well-watered.
- Wet, poorly drained soil - select suitable, well-drained planting sites.
- Herbicide damage - twigs are stunted and distorted. Avoid drift by spraying on calm days; follow label instructions carefully when applying herbicides.
Bark is cracked longitudinally
- Frost/freeze cracks, sunscald - cracks usually occur on the south or west side of the 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. Therefore, avoid late summer-early fall pruning or fertilizing.
- Trunk bark/wood is gouged or scarred - lawnmower or string trimmer injury. To protect the trunk, mulch around the tree to within 6 inches of the trunk. Or embedded wires or collars from tree support apparatus. Stone fruits do not need physical support.
Water sprouts, root suckers
- Caused by environmental stress and removal of large branches and limbs - prolific growth of sprouts occurs directly below large pruning cuts. In all cases promptly pull or cut all water sprouts at the point of attachment.
Bulging or deformity of the trunk at the graft union
- Normal on grafted trees for scion wood to over-grow or under-grow the rootstock. Remove all suckers that arise below the graft union. If graft union is damaged or killed, sucker growth may outgrow desired scion stock.
Fruit and Flowers
Blooms are brown and either dry or watersoaked (blasted)
- Late spring frost.
Damaged buds (cross-section reveals brown tissue). Buds cut lengthwise will be brown inside
- Winter-kill of buds - sustained periods of very cold temperatures.
- Spring frost damage to buds and flowers - trees may leaf out without flowering. Leaf buds are hardier than flower buds. Open blooms are more cold-sensitive than closed buds. Avoid planting in low areas or frost pockets. If possible, cover small trees with a tarp or other light cover if a frost is expected.
- Misuse of dormant oil sprays or pesticide sprays: including spraying when temperatures are below 40°F. Over-spraying of dormant oil, lime-sulfur, and other fungicides and insecticides may damage leaf and flower buds and blooms. Follow label directions.
- Water stress - causes drying out of leaf and flower buds. Irrigate during dry periods.
- Lack of pollinizer trees (a second variety) - applies to most sweet cherries and Japanese plums, and apricot-plum crosses. 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. Especially a problem on cross-pollinated species (most sweet cherries and Japanese plums, apriums, and plumcots).
- Spraying insecticides during bloom period - kills pollinators. Do not spray insecticides during the bloom period.
- Overuse of nitrogen fertilizers prior to bloom period - reduce applications of high nitrogen fertilizers.
Failure to fruit, minimal fruit set
- Winter-kill of buds - sustained sub-freezing temperatures. Spring frost damage to buds and flowers.
- Low light conditions; excessive shade. Follow proper thinning and pruning guidelines. Situate plantings for optimum light exposure.
- Low-temperature damage - trees may leaf out without flowering. Leaf buds are hardier than flower buds. Select late blooming cultivars.
- Lack of pollinizer trees: (a second variety) - applies to most sweet cherries and Japanese plums, and apricot-plum crosses.
- Poor pollination/fertilization - bee activity is low during cool, wet weather.
- Spraying insecticides during bloom period - Not recommended because it kills pollinating insects.
- Spraying dormant oil or Bordeaux on open blooms - may damage tender tissue.
- Over-use of nitrogen fertilizers.
- Severe pruning - will reduce the number of blooms. Do not prune out fruit-bearing wood during the dormant season.
Premature fruit drop
- Natural thinning: “June drop” (peach) - peach trees over-produce fruit and thin themselves naturally.
- Late spring frost - May damage or kill buds and developing fruits. Don’t plant trees in low, cold areas susceptible to late frost.
Small or undersized fruits
- Failure to thin or prune properly - thin to reduce the number of fruit or blossoms.
- Low soil fertility - Follow soil test recommendations.
- Excessive moisture during ripening (sweet cherry especially vulnerable) - pick ripened fruit promptly and use mulches and irrigation to maintain even soil moisture.
- Split pit disorder: (peach and nectarine); the opening of the pit at the stem end - a physiological problem that can lead to secondary insect and disease problems. Occurs more on early season cling-type peaches. Encouraged by severe thinning, excessive rainfall, and excessive nitrogen fertilization.
External damage on peaches
- Pesticide burn - spots in a pattern or russeting. Captan®, sulfur, and oil sprays may produce russeting on sensitive varieties.
- Hail - small, roughened areas on fruit. Cosmetic damage. Should not affect eating quality.
- Mechanical damage - skin is torn, gum buildup. From contact with branches or rough handling.
- Sunscald - white, tan, or brown sunken areas on exposed surfaces. May alter fruit flavor. Remove and discard affected fruit.