The Pro Farmer

Fusarium wilt / crown root rot

The fusarium fungus harms the root, and the water & minerals transport tissues (xylem and fluem), in the plants. Expressed in the wilting of the leaves, root rot and a significant reduction in yield. The fungus harms many species, including banana, lettuce, potato, tomato, melon, watermelon and cucumber. The fungus spores can survive in the soil, sometimes for more than a year; it can also survive on other things such as pots, benches, irrigation equipment and pipework, tanks of nutrient solution and plant debris. It can live at great depth (100 to 150 cm). The spores which are drought-resistant can be spread in air and in dust. Insects and mites also can spread spores. Spores produced in massive numbers and can also be spread during handling of the plants or by watering. It settles in the tip tubes and leads to clogging. The incubation period is from 2 to 13 weeks.

Watermelon plants in the greenhouse wilting due to fusarium
Watermelon plants in the greenhouse wilting due to fusarium

The infected plant suffers from a significant shortage of water and nutrients leading to the appearance of symptoms of wilting. The plant appears thirsty and as the disease progresses the leaves lighten and wither and later death of the plant. Young plants may show no immediate symptoms even though infected. The stem of the plant dries out and becomes hollow. A cut in the stem will reveal the core is dry but white. Chocolate brown lesion girdles the main stem just above the soil line.
Reddish to brown discoloration of the stem cortex when sliced lengthwise. In many cases it will be possible to see signs of recovery at night, when there is a drop in the temperatures, but as the disease progresses the whole plant will show signs of wilting without recovery.

Brown lesion created by fusarium, girdles the main stem just above the soil line
Stem of Tomato plant infected with fusarium
Wilting tomato plant attacked by fusarium

A proper soil disinfection in this case, will reduce or kill all the fungus spores, however it will not prevent from other fusarium spores to come from other places dew to their ability to be airborne. Without soil disinfection there will be an enormous quantities of fusarium spores in the ground which will contaninate immidiatly, all the new seedlings of the new season. After 2 months all the plants in the plot will be infected and wilt. Soil disinfection will only postpone the infection of the plants, due to the reason that these spores will arrive with the air/dust/insects, and contaminate the roots. Wilting plants will appear after 3 months, when first harvest starts. So the two ways to deal with it, is using plants that have fusarium resistance or using a rootstock that have a resistance to fusarium. But there is a third way. PROCHLORAZ is a fugicide that can protect the root during the first month. FLUDIOXONIL is also a fungicide that protects the root from fusarium. This method have almost 100% of success. The fungicide is best applied through the drip irrigation system, 3 times. 1. one week after planting 2. Three weeks after planting 3. five weeks after planting.

You can choose to use PROCHLORAZ or FLUDIOXONIL , but not the both of them together. The amount is 0.15cc of PROCHLORAZ per plant for each time, so each plant get around 0.45cc per season. The amount of FLUDIOXONIL is 0.05cc per plant each time, so each plant get 0.15 cc per season.

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