Control Methods for Tomato Rot and Stem Base Rot

[Control of Tomato Fusarium Wilt]

Tomato Fusarium wilt is caused by the pathogenic fungus Fusarium oxysporum f. sp. Lycopersici. When seedlings are infected, they wilt and die rapidly. It generally occurs in the mid-to-late stages, first with vein clearing and epinasty, then gradually yellowing and wilting from the lower leaves upward. In the early stage, symptoms often appear on only one side of the plant, after which the petioles droop and the entire plant dies (Figure 1). When the stem is cut open, the vascular bundles can be seen to have turned brown (Figure 2), but there is no white turbid bacterial ooze as in bacterial wilt, which can be used to distinguish the two diseases. Tomato Fusarium wilt is another highly troublesome disease in tomato cultivation in the Taitung area. This disease is a soil-borne disease that is difficult to control and shows an increasing trend of spread. This article briefly introduces its disease characteristics and control methods.

 

After the chlamydospores of this fungus germinate, the germ tubes penetrate directly from the tomato root tips or through wounds. When the hyphae encounter the vessels, they grow upward and downward and can also move upward with the water flow. Before the diseased plant shows wilt symptoms, slight browning can already be found on the vessel walls; then the tissue around the vessels turns brown, the leaves wilt and die, and finally all remaining parts of the diseased plant wilt. At this point, the pathogen develops to the plant surface, produces conidia, and spreads by wind or water. When soil moisture is high and temperature is low, the pathogen can develop onto the fruit, and the seeds then carry the pathogen. Therefore, in addition to soil transmission, this disease can also be transmitted through seeds.

 

This fungus grows best at a soil pH of 7 to 8, and the optimum soil temperature is 28°C. When the temperature is above 33°C or below 21°C, the occurrence of this disease is suppressed, meaning it mainly occurs in the mid-to-late growth stages.

 

The officially recommended control chemicals for this disease are still under testing. At present, appropriate cultivation management practices remain the control strategy, with the following key points:

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1.

Plant disease-resistant grafted seedlings and clean seedlings.

2.

Because this disease is mainly transmitted through soil, when diseased plants are found, they should be immediately removed together with the surrounding plants, and irrigation should be minimized to avoid spread.

3.

Adjust the soil pH to 6~7.