Compacted, poorly-drained soils, nutrient imbalances, unsuitable soil pH, air pollution, limited air circulation/plant crowding, road salt injury, improper plant installation practices, inappropriate light levels, and poor irrigation practices are among the most common factors that create plant stress and may result in increased susceptibility to certain diseases. These factors are chronic stresses that weaken the plant over time. Months, years, or decades may be involved before the cumulative effects result in visible problems. Sometimes the chronic stress itself over a period of time will cause the plant to decline and eventually die without involvement of a pathogenic organism. These types of problems that are not caused by pathogenic organisms are generally referred to as 'disorders,' or 'abiotic' or 'noninfectious' diseases.
The prevention of infectious as well as non-infectious diseases linked to chronic stress from environmental factors depends on wise landscape planning and management. Choosing appropriate plants and materials for the site, appropriate site preparation and careful maintenance will go a long way towards avoiding plant health problems. An understanding of the cultural requirements of landscape ornamentals is essential to alleviating plant health problems related to chronic stress.
Acute environmental stress is linked to a single event and, like chronic stress, may sometimes predispose a plant to disease. Damage from drought, cold, wind, hail, and mechanical damage are all examples of acute stress. Unlike chronic stress that occurs over time, acute stress occurs suddenly and causes damage soon after it occurs. With chronic stress, there may be time to reverse an imbalance if it is recognized early; however, with acute stress there is little or no time to prevent plant damage.