Diseases, pests and stressful environmental conditions can lead to severe wilting in shrubs, trees and garden plants. Identifying the cause of wilting and applying the appropriate management tactics is critical for saving the plant or preventing contagious ailments from affecting surrounding vegetation. Wilting plants often suffer from multiple problems -- for example, a fungal disease accompanied by an insect infestation -- which makes diagnosis and recovery more difficult.
Fungal pathogens are responsible for hundreds of diseases of trees, shrubs and herbaceous plants throughout North America. Some fungi cause wilt diseases that damage various tissues and lead to a severe decline in the plant's health. Fusarium wilt, caused by fungi in the Fusarium genus, decays the leaves, roots and stems of its host. Wilt diseases cause significant loss of vigor, discoloration of green growth and possibly death of the entire plant. Early symptoms of fusarium wilt may be localized, with only one shoot or section of the plant showing signs of infection before the entire plant wilts, according to Ohio State University. Species in the fungal genus Verticillium also cause a widespread wilt disease of garden plants and trees.
Tobacco mosaic virus, cucumber mosaic virus and tomato spotted wilt virus cause fatal symptoms in a number of plant species, including tomatoes, tobacco and cotton. The symptoms of a viral infection varies significantly, but many of them cause severe wilting and loss of foliage. TSWV produces dark streaks on the stems of its host, white spots on its fruit and heavy foliage loss. Viral diseases are often transmitted by parasitic insects, like thrips and aphids, but they can also spread through the soil or via gardening tools. Removing infected plants and controlling insect pests helps prevent the spread of pathogenic viruses.
Some insects can deal enough damage to the stems, leaves or roots of a plant to cause severe wilting of foliage and green growth. Infestations of squash bugs and vine borers are extremely damaging to pumpkins and squash in some regions of the United States. These insects cause a number of symptoms, including discolored foliage, holes in stems and partial wilting. Root knot nematodes (Meliodogyne spp.) are tiny worms that infest the roots of garden plants, shrubs and trees. An infestation of nematodes causes deformed, ball-shaped growths, called galls, along the roots of their host. This damage inhibits the plant's ability to absorb nutrients, which can lead to a dangerous mineral deficiency, and decreases its resistance to fungal diseases, according to Kansas State University. Infested plants may wilt periodically and produce stunted or deformed growth.
Exposure to toxic chemicals, nutrient deficiencies and other environmental factors can harm plants, causing them to wilt and exhibit other serious symptoms. An excessive or insufficient supply of moisture is a common cause of wilting. Heavy soils that become saturated easily are not suitable for most ornamental and vegetable species. Soils deficient in minerals like potassium, copper and chlorine may cause wilting leaves and other damage to plants. Plants growing near walnut trees may wilt from exposure to juglone, a toxic chemical produced by the black walnut (Juglans nigra) that is spread throughout the soil in a large radius around the tree.
- North Carolina State University: Action Mode, Deficiency and Toxicity Symptoms of the 17 Essential Nutrients
- Ohio State University Extension: Fusarium and Verticillium Wilts of Tomato, Potato, Pepper, and Eggplant
- University of Minnesota: Squash Bug
- University of Kentucky: Squash Vine Borer and Squash Bug
- Kansas State University: Wilt, Nematode, and Virus Diseases of Tomato
- University of Minnesota: Mulching and Watering
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