Fusarium Wilt on Okra

From Clemson Plant Pathologist Tony Keinath.

Late summer is the time of year when Fusarium wilt shows up on okra. Because the fungus travels in the xylem, external symptoms are visible on all above-ground plant parts. Although the main stem may remain partially green, side branches turn brown, and pods dry completely.

Plant Pathologist Ginger examines dried shoots and pods on an okra plant affected with Fusarium wilt.

To diagnose Fusarium wilt, cut the main stem of an affected plant along its length. Extensive, reddish brown vascular discoloration confirms Fusarium wilt.

Reddish brown vascular discoloration on ‘Clemson Spineless’ okra affected with Fusarium wilt.

Fusarium wilt of okra (Abelmoschus esculentus) is caused by Fusarium oxysporum f. sp. vasinfectum, the same special form (“forma specialis,” f. sp.) that causes Fusarium wilt of cotton (Gossypium hirsutum). Botanically, okra and cotton are members of the Malvaceae (mallow) family and the Malvoideae subfamily. These two hosts, however, are members of different tribes, the botanical unit that is smaller than a family but larger than a genus. Thus, this Fusarium wilt fungus has a wider host range than other Fusarium wilt fungi, which typically infect one main plant species.

In August 2020, Fusarium wilt was found on ‘Clemson Spineless’ okra on a farm in Upstate South Carolina. The okra was growing in a field that had not been planted to cotton for 20 years. The grower had been following a good crop rotation of strawberries (non-host), okra, and tomatoes or cucurbits (non-hosts). However, it appears that 2 years between okra crops in the same field is not enough to prevent Fusarium wilt. Crop rotations should include 3 years of non-host crops between crops of okra.

It’s assumed that all okra cultivars are susceptible to Fusarium wilt. During the winter I will be testing okra cultivars recommended in the 2022 Southeast Vegetable Crop Handbook to check susceptibility. If you have a favorite okra cultivar you would like me to include in the test, please email me by Oct. 1.

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