Fusarium wilt on tomatoes: identify, prevent, replace

A tomato plant that yellows on one side while the other side stays green is sending a clear signal. That asymmetric wilt -- a single branch or half the plant yellowing before the rest -- is one of the most recognizable signatures of Fusarium wilt, a soilborne fungal disease that kills plants from.

A tomato plant that yellows on one side while the other side stays green is sending a clear signal. That asymmetric wilt — a single branch or half the plant yellowing before the rest — is one of the most recognizable signatures of Fusarium wilt, a soilborne fungal disease that kills plants from the inside out. By the time you see it, the infection is already weeks old.

I don't grow tomatoes at my Long Island property — the deer pressure and available space have kept me focused on ornamentals — so this guide draws entirely on University Extension and USDA research.

What causes Fusarium wilt

Fusarium wilt is caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici. Per Cornell Cooperative Extension, this pathogen is host-specific to tomatoes and does not infect other solanaceous crops such as peppers or eggplant. Two races are common in North America: Race 1 and Race 2. A third race (Race 3) has been documented but is less widespread.

The fungus colonizes the plant's vascular system — the xylem vessels that carry water and nutrients — blocking water transport and causing the characteristic wilt even when soil moisture is adequate.