These wilt diseases are all soil-borne and can persist for many years in the soil even if no host plants are grown. They can also be brought into a garden on infected transplants or soil. Fusarium wilt does not spread above the ground from plant to plant.
Fusarium wilt is caused by a soilborne fungus that is able to survive in the soil without a host for up to ten years. Ideal conditions include warm soil temperatures, acidic soil pH (5.0 - 5.5), and high humidity.
If fusarium wilt hits your garden, don't plant the same or related plant types in that area for at least four years. Depending on your climate, it may be possible to control fusarium wilt by "solarizing" your soil. This involves covering it with plastic so it reaches very high temperatures over a long period.
Isolation and Identification of Fusarium Species
Three methods, namely soil dilution agar plates, debris isolation and direct isolation, were used to isolate species of Fusarium from mangrove soil. These techniques were based on the methods described in The Fusarium Laboratory Manual (Leslie & Summerell 2006).
Bacterial wilt is caused by the bacterium Ralstonia solanacearum. The bacterium can survive in the soil for several years, even in the absence of a host plant. It infects the plant through its roots and moves up through the vascular system, where it multiplies and blocks the flow of water and nutrients.
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.
Treating fusarium wilt of tomatoes is not possible. Affected branches or entire plants can only be destroyed, as they will die eventually. Prevention is the only way to avoid the damage of fusarium wilt in your tomato garden. Start with varieties that resist the disease.
To effectively kill fungus in soil, removing infected soil and treating both soil and plant roots with fungicides or natural remedies like bicarbonate of soda mixed with water is important. Addressing soil fungus promptly can prevent it from spreading and harming other plants.
Synthetic fungicides are widely used to control wilt diseases. Thiophanate-methyl was found to be effective against Fusarium wilt disease when applied as a soil drench and a seed dresser3.
Avoid over-watering: Over-watering can increase the chances of Fusarium Wilt because the fungus thrives in moist soil.
For Fusarium oxysporum f. sp. lactucae, the pathogen which causes Fusarium wilt of lettuce, the required temperature for control is generally taken to be > 140°F for 20 minutes.
Plant cultivars of vegetables with resistance to Fusarium and Verticillium wilts. Cantaloupes, peas, and tomatoes have a wide selection of resistant varieties whereas other crops have limitations (Table 3).
The Fusarium oxysporum life cycle, is similar to that of most Fusarium species. Fusarium overwinters for many years in the soil and on crop residues of infected plants as chlamydospores (thick walled mycelium cells) or mycelium. Survival is also possible on seed, greenhouse structures, tools and machinery.
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.
Sclerotia allow the fungus to survive in the soil and plant debris for 5 or more years. In spring and summer when temperatures are cool (51 to 68 F) and the soil is moist, sclerotia produce a few tiny mushrooms. These mushrooms release spores that can travel up to a mile or more by wind.
Fungi can be remarkably drought tolerant—they can remain active and even grow under extremely dry conditions [1, 2]. Similarly, fungal abundance can increase under drought [3–8].
Check soil regularly. Removing mushrooms before they're big enough to produce spores will help slow the spread. Putting fine gravel on the surface of the soil can prevent fungus taking hold. Some people also swear by cinnamon, a natural fungicide, sprinkled on the soil.
Fusarium can survive in soil for 5-10 years, surviving as saprophytes (lives on dead/decaying organic matter) in plant debris in soil indefinitely and producing dormant and tough resting spores.
Fusarium wilt affects the productivity of tomato plants and may lead to death, but the fruit is still edible.
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.
Fungal and bacterial wilts display many of the same or similar symptoms of other plant diseases and disorders, making diagnosis sometimes difficult. However, the most prominent symptom in fungal wilts is xylem vascular discoloration and in bacterial wilts the presence of bacterial ooze, vascular discoloration and rot.
Heat is the only practical means of treating soil physically. Complete treatment, or sterilization, requires heating soil to 2120 F. Partial treatment, or pasteurization, requires heat of 140 to 1600F.
Chemical Control
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.