Verticillium wilt tends to develop during the cooler periods of late spring. Symptoms of this disease are similar to Fusarium wilt. Older leaves are affected first; they turn yellow, wilt and eventually drop from the plant.
The first symptoms appear when fruit begins to mature. Lower leaves turn yellow, sometimes on one side of the plant or one side of a branch. This is followed by leaf and stem wilting. When an infected stem is scraped or split lengthwise you will see browning of the vascular tissue (the tissue closest to the "skin").
Symptoms and Signs
Older leaves on tomato plants infected with Verticillium appear as yellow, V-shaped areas that narrow from the margin. The leaf progressively turns from yellow to brown and eventually dies. Older and lower leaves are the most affected.
Symptoms include yellowing, stunting, and death of seedlings and yellowing and stunting of older plants. Infected plants wilt readily, lower leaves yellow and dry, the xylem tissues turn brown, and the plant may die. In the early stages of disease, the roots are not rotted.
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 first noticeable symptom of Verticillium wilt is sudden, abnormal wilting of branches. 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.
The first symptom is wilting of a few leaves. This often goes un-noticed. Soon thereafter, the entire plant wilts suddenly and dies. Such dramatic symptoms occur when the weather is hot (86-95 F), and soil moisture is plentiful.
There is no effective fungicide or other cure for Fusarium wilt. The pathogen nearly always kills infected hosts. Prevention and exclusion are the only effective management strategies. Avoid this problem by replanting at that site using species from different genera than plants previously infected there by Fusarium.
Avoid over-watering: Over-watering can increase the chances of Fusarium Wilt because the fungus thrives in moist soil.
Colonies are usually fast growing, pale or bright-coloured (depending on the species) with or without a cottony aerial mycelium. The colour of the thallus varies from whitish to yellow, pink, red or purple shades. Species of Fusarium typically produce both macro- and microconidia from slender phialides.
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.
Symptoms and Signs
Initially, symptoms of Fusarium wilt of tomato appear as one-sided wilting of only half of the plant, branch, or leaflet. At first, the plant will appear to recover from the wilt, but as the disease progresses, it will become permanent regardless of temperature or water status.
How to Control Verticillium Wilt: There is no effective treatment for verticillium wilt.
Symptoms. Initial symptoms of Verticillium wilt include yellowing of the lower leaves, wilting, stunted growth, and v-shaped lesions that extend inward from the margin of the leaf. Brown, necrotic tissue begins to develop within the lesions as the disease progresses.
Prochloraz and bromuconazole were the most effective fungicides against the pathogen both in vitro and in vivo, followed by benomyl and carbendazim. All other fungicides were less effective.
Peeling the epidermis (outer tissue layer) off the lower stem will reveal dark red and brown discolored vascular tissue. Confirm diagnosis by sending a plant sample to the University of Minnesota Plant Diagnostic Clinic, as this disease is easily confused with Verticillium wilt.
Symptoms. Leaves on infected plants turn yellow and fall. The plant wilts over several days and then dies. A characteristic symptom of fusarium wilt is the reddish-brown discolouration of the water conducting tissue of the stem and roots, seen when these parts are cut with a sharp knife.
How to Control Fusarium Wilt: Once fusarium wilt infects a plant, there is no effective treatment. Remove and dispose of affected plants immediately; don't compost this garden refuse. Whenever possible, remove and replace fusarium-infected garden soil.
Bacterial ooze from a freshly cut stem. This is unique to bacterial wilt and pith necrosis, and is not seen in case of Fusarium wilt/crown root rot and Verticillium wilt.
The significant reduction of fusarium wilt disease in tomato plants treated with neem extract could be due to the presence of gedunin i.e. tetranortriterpenoid which posses antifungal properties (Sadre et al., 1983) or due to presence of Azadirachtin (tetranortriterpenoid).
There are three strains of fusarium, the following are listed as having resistance to at least one. Resistant varieties for garden tomatoes: Sun Start, Sunny, Daybreak, Mt. Spring, Mt. Fresh, Celebrity, Floralina, Jet Star, Merced, Sunmaster, Sun Leaper, Carolina Gold.
Prothioconazole is the only commercially available fungicide with proven efficacy. Azoxystrobin, prothioconazole and thiophanate-methyl led to the highest values for reduction of Fusarium wilt and did not cause phytotoxicity in watermelons.
Unfortunately there is no cure for fungal wilt diseases, so infected plants should be removed and discarded, but do not place diseased plants in the compost pile. Management techniques can be used in the home vegetable garden to control Verticillium and Fusarium wilt.
The variety Cobra 26 showed the lowest incidence of bacterial wilt during the two experiments (15% and 17.5%, respectively) which was not significantly different from that of the tested resistant varieties PADMA and Hawaii 7997 for which the IBW was 0%.
Once bacterial wilt infects a plant, there is no way to control the disease. The bacteria cannot transmit in seed, does not survive in soil, and only survives in plant debris for a short period.