Hosts include ash, box elder, camphor, catalpa, Chinese pistache, coral tree, dracaena, dodonaea, elm, fuchsia, hebe, Indian hawthorn, maple, mayten, olive, pepper tree, redbud, rose, syringa, and tulip tree. Various flowering herbaceous plants and garden vegetables are also susceptible to Verticillium wilt.
Plants affected include Chrysanthemum, carnation, aubergine, potato, tomato, cucurbits and strawberries. Woody plants are also affected, including Acer, Cotinus, Rhus, Berberis, Catalpa, Cercis and Rosa, but the full host range is very large. Conifers are not affected.
Symptoms of verticillium wilt can be confusing because they are so variable. They include marginal scorch and complete wilting of leaves on individual branches in the crowns of potential hosts. Symptoms can occur at any time of the year but often show up when hot, dry weather begins.
Control of Verticillium Wilt
Verticillium wilt can't be cured once it enters the plant. It's best to remove and destroy small, easily replaced plants. The disease remains in the soil after you remove the plant, so don't plant another susceptible species in the same area.
The fungus survives in the soil as a thread-like body called a mycelium and as microscopic, dark, resistant structures called microsclerotia. These microsclerotia can survive in soil or dead plant material for up to ten years. For this reason, it is virtually impossible to eradicate the fungus from the soil.
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Laboratory experiments have shown that to kill V. albo-atrum in hop bine fragments it is necessary to maintain a temperature of 40°C (104°F) for at least 7 days, 45°C (113°F) for 12 hours, 50°C (122°F) for three hours, or 60°C (140°F) for 15 minutes.
Laboratories that analyze soil samples for Verticillium report results in number of sclerotia per gram of soil. Where a single (susceptible) cotton variety is planted without rotation: A level of 10 or more microsclerotia per gram usually results in significant yield loss.
The major differences in these wilts are: 1) The fungi proceed slowly in the host relative to bacteria and produce more uniform symptoms through the plant. 2) In bacterial wilt, symptoms appear from the top down, whereas in Fusarium and Verticillium wilt, symptoms begin at the bottom of the plant and progress upward.
The disease is favored by cool soil and air temperatures. Verticillium wilt is difficult to distinguish from Fusarium wilt and positive identification may require cultivating the fungus in a laboratory. Verticillium wilt seldom kills tomato plants but reduces their vigor and yield.
Both fungi invade the plant through the fibrous root system and disrupt water and mineral uptake within the plant. Infection and disease development in Fusarium wilt are favored by warm soil temperatures (80° F) and low soil moisture, while Verticillium wilt develops best at relatively cool (55-75 F) soil temperatures.
Verticillium wilt can affect all cucurbits.
Some of the common woody hosts include ash, black locust, catalpa, dogwood, elm, magnolia, maple, red bud, Russian olive, sumac, tulip tree, viburnum, yellow poplar, and yellow wood. Verticillium wilt is also a common disease of many crop plants such as cotton, eggplant, potato, and tomato.
Vegetables commonly and severely affected by Verticillium wilt include tomato, potato, pepper, eggplant, cucumber, muskmelon, pumpkin and watermelon.
Depending on where you live, you may be able to control verticillium wilt through professional soil fumigation or other means. In warm climates, plastic-covered soil may reach temperatures high enough to suppress the fungi at fault.
They also develop a variety of symptoms that include wilting, curling, browning, and drying of leaves. These leaves usually do not drop from the plant. In other cases, leaves develop a scorched appearance, show early fall coloration, and drop prematurely (Figure 2).
Groups of plants resistant to verticillium wilt include gymnosperms, monocots, members of the rose family, oaks, dogwoods, willows, rhododendrons, azaleas, and others.
Trees and shrubs infected with Verticillium cannot be cured and will likely eventually die. However, you can extend the life of your plants by making sure that you water and fertilize them properly. Make sure established trees and shrubs receive approximately one inch of water per week.
Wilting may occur on only one side of a plant. Heavily infected plants can succumb quickly and if not removed can release the survival structures into the nearby environment where they will wait for the next host to repeat the cycle. The disease can spread from root to root and through infected seed (up to 13 months).
Verticillium has no known perfect stage. The life cycle is an endless repetition of an asexual reproductive cycle (Fig. 42-5). The genus, Verti- cillium is recognized by the hyaline, branched conidiophores which are verticillate, or whorled.
Leaves may yellow or brown prematurely and branches may appear scorched or show dead and dying twigs. Sapwood may appear discolored below the surface of the bark. In other woody plants and ornamentals, discoloration and browning are the first symptoms of the disease.
This disease, mainly caused by Verticillium (V.) dahliae or albo-atrum fungal species, penetrates plants through their roots and spreads upwards. As the infection progresses, it causes damage to the plant's vascular system, resulting in wilting leaves and eventual dieback.
Remove infected crop residues and regularly disinfect tools and machinery to reduce inoculum spread. Pull out diseased plants with their roots and dispose of them away from production fields. For irrigation systems, use chlorination or other approved water treatment methods to prevent Fusarium wilt spread. Plant care.