Common Cultural Disorders of Plants
Cold injury: Freezing injury can cause death or dieback. Symptoms of cold stress are stunting, yellowing, bud or leaf drop, and stem cracking. Fruit may form a layer of corky tissue or be russeted if exposed to cold when young.
Heat injury: Temperatures that are too high cause sunscald of fruits, leaves, or trunks on the sunny side of the plant. Discoloration, blistering, or a water-soaked and sunken appearance are other symptoms of heat stress.
Moisture imbalance: Plants need a relatively constant supply of water. If they don’t have enough, they will wilt. Long periods of wilting, or repeated wilting, can cause stunting, pale color, and reduced flowering and fruit production. Plant roots also need oxygen. Too much water in the soil damages roots and will cause symptoms like frequent wilting, pale color, root decay, leaf dropping, and lack of vigor.
Wind damage: High winds also take their toll on plant appearance. Silvery discoloration and tattered leaves are symptoms of wind damage.
Salt damage: Ocean spray and road salt, as well as animal urine, can injure plants. Salts can accumulate on leaves, stems, and buds, or build to toxic levels around the roots. Over time, salt burn weakens the entire plant and causes droughtlike symptoms.
Ozone damage: Ozone is a common air pollutant that can cause a wide range of symptoms in susceptible plants, including withered leaves on citrus and grapes and tipburn on conifers. If you confirm that ozone is a common pollutant where you live, your only recourse is to avoid planting sensitive species.