Fusarium Wilt

Fusarium wilt was first described by G.E. Massee in England in 1895. Today it has been reported in at least 32 countries worldwide. Some symptoms of Fusarium are as follows:

Infected Seedlings:

• Stunted growth

• Older leaves may droop and curve downward (some might turn yellow)

• Vascular tissue can become a dark brown

• The bases of some affected stems enlarge

• Plants may wilt and/or die

Older Plants:

• Yellowing of older leaves (this often happens on one side of the plant)

• Wilting of the plant

• Vascular tissue is usually a dark brown (extending from the stem and is especially noticeable in the petiole scar)

• Fruit infection occasionally occurs and can be detected by the vascular tissue discoloration within the fruit

Click photos to enlarge

Disease Cycle

Fusarium wilt is a warm-weather disease, most prevalent on acid sandy soils. The pathogen is soil borne and remains in infested soils for several years. Invasion occurs through wounds in the roots growing through infested soil. In general, factors favoring wilt development are soil and air temperatures of 28°C, a soil moisture optimum for plant growth, plants preconditioned with low N and P and high K, low soil pH short day lengths, and low light intensity.

Control

Use resistant cultivars for the control of races 1 and 2. Monogenic resistance to race 3 has been identified. Use resistant cultivars, when available for the control of this race.

Pasteurization of the infested soil with steam or fumigants reduces the instance of wilted plants and greatly increases marketable and total yields.

Raise the soil pH to 6.5-7, and use nitrate nitrogen rather than ammoniacal nitrogen. This significantly retards disease development and results in yield increases equal to those gained by injecting fumigants into 5.5 pH soil.

Prevent movement of Fusarium-infected seed and plants and Fusarium-infested soil clinging to machinery, transplants, vehicles, tools and stakes into areas free from the pathogen. Do not irrigate with ditch water or pond water, because surface water might be contaminated with the pathogen. Keep tomato fields away from seedlings production houses or seedbeds. A 5 - 7 year crop rotation does not eliminate the pathogen but greatly reduces loss.

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