Leaf Scorch
Multiple causes: drought, salt, wind, Xylella fastidiosa (bacterial leaf scorch)
Overview
Leaf scorch is a physiological browning of leaf margins and tips caused when water loss from leaves exceeds what roots can supply. Drought, hot wind, salt, root damage, compacted soil, and reflected heat from pavement are common drivers. Unlike infectious leaf blights, scorch usually lacks pathogen signs and follows weather extremes. Trees with limited root zones, new transplants, and evergreens exposed to winter wind are frequent victims. Improving the soil-root environment is more effective than foliar sprays.
Symptoms
Leaf edges turn tan, brown, or black while the center may stay green longer. A yellow halo sometimes separates dead margin from living tissue. Scorch often appears first on the sunny, windward side of the canopy or on the most exposed leaves. Entire leaves may drop prematurely after severe episodes. On evergreen broadleaves, winter browning of margins is common. There is usually no fungal fruiting body or bacterial ooze in classic abiotic scorch.
Environmental Conditions
Hot
Prevention
Plant species adapted to local summer heat and wind. Design beds with mulch, windbreaks, and soil organic matter that hold moisture. Avoid planting sensitive trees in narrow parking-lot islands without irrigation plans. Water thoroughly before predicted heat and drying winds. Protect evergreen foliage from winter desiccation with antitranspirant practices only when appropriate, or better, with windbreaks and adequate fall watering before ground freeze.
Management
Deep-water during drought, especially for recent transplants and shallow-rooted trees. Apply wood-chip mulch over the root zone, keeping it off the trunk flare. Reduce competition from turf against tree roots. Temporary shade can help newly planted shrubs through heat waves. Do not fertilize heavily during severe drought. Prune only dead wood after you confirm dieback; live twigs with scorched leaves may still recover next season if buds are sound.