We usually think of plant problems as due to pests or diseases: Biotic agents! These living organisms include insects, disease causing pathogens, nematodes, parasitic plants, and viruses. But abiotic—nonliving agents—can also injure our landscape plants. If you think about it, you’ve probably lost plants to many of these, which include environmental extremes in moisture and/or temperature; mechanical damage, such as severe root cutting; and chemical factors, such as high soil salinity or herbicide damage.
Accurate diagnosis is key to remedying any plant problem, biotic, abiotic, or both!
How to diagnosis?
• Identify the plants: Determine the botanical name: genus, species and family—plant labels usually have plant genus and species and with that information you can look up the plant family.
• Identify the symptoms: Chlorotic (yellowing), necrotic (blackening or death), or distorted plant parts. Be thorough and accurate!
• Inspect the whole plant: Examine all parts of the plant, not just the injured area.
• Look for patterns: Are symptoms uniform throughout the plant or scattered?
• Inspect the site: Is the soil well-drained, is there recent evidence of disturbance, how long has the plant been in the ground?
• Do you have any records of plant care—watering, fertilizing, pruning, spraying?
• Identify likely causes from the information collected— Keep in mind that there may be multiple causes!
• Collect samples and submit for testing to rule out disease or insect problems at the North Carolina Plant Disease and Insect Clinic.
Examples and symptoms of common environmental abiotic plant problems:
Water—Too much or too little—both can damage plants! Waterlogging kills roots if oxygen levels in the root zone are too low, but excess soil moisture is more commonly a factor in root disease. At the other extreme, insufficient moisture can result in scorch symptoms on foliage, stunting, leaf yellowing, leaf drop, early Fall color; and death of flowers and fruits.
Sunscald usually occurs in late winter or early spring when sunlight heats tree bark during the day. This causes the water in the ground to start to rise from the roots. With freezing nighttime temperatures, this water freezes within the bark tissue and an elongated canker can form that appears discolored and sunken. Cracking and peeling bark may follow. It may be the next spring or summer when new growth occurs before the damage shows. Tree with thin bark such as beech (Fagus), dogwood (Cornus), honey locust (Gleditsia triacanthos), linden (Tilia), mountain ash (Sorbus americana) and sugar maple (Acer saccharum), and newly planted trees are especially susceptible.
Wind moving across leaves takes moisture from them, sometimes in excessive amounts resulting in a scorched appearance. Evergreen trees and shrubs are particularly susceptible to this during the winter when the roots cannot extract water from frozen soil.
Low temperature—Plants have critical temperature levels at or below which they may experience frost or freezing injury. Plant cells are injured when the temperature falls below a critical level for a species. Injury at above freezing temperatures is called chilling injury. Such injury may affect any plant parts of both evergreen and deciduous plants. Young leaves are most sensitive to lower temperatures; injured leaves look water soaked and black. Flowering plants putting on new growth are especially susceptible. It may be a few weeks before you see damage from cold temperatures. To minimize injury from low temperatures be sure to select plants that are hardy in your area—Zones 5b to 7a, depending where you live in Buncombe county.
Article by Bob Wardwell, Extension Master GardenerSM Volunteer
Abiotic Disorders of Plants https://content.ces.ncsu.edu/extension-gardener-handbook/5-diseases-and-disorders#section_heading_7612
Sunscald of Woody Plants www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/environmental/sunscald/sunscald-of-woody-plants.aspx
Abiotic Disorders of Landscape Plants: A Diagnostic Guide, Costello, L., et al., University of California Press, February 2014.
How to submit a sample for Insect and disease identification: https://projects.ncsu.edu/cals/plantpath/extension/clinic/submit-sample.html