To Fight Fusarium Wilt in Your Watermelon Crop, ID It Early
May 4, 2022 There are over five million fungal species that exist in the world but it takes only one to overwhelm watermelon disease management strategies and damage roots – Fusarium oxysporum f.sp niveum. Infecting only watermelon, this pathogen causes fusarium wilt. The most widespread and economically damaging watermelon disease in the Southeast, fusarium wilt can reduce yields by 40-80%[1], depending on the severity of the disease. And it can have a dire affect an operation’s bottom line.
How it Begins
Plants under stress don’t fight off disease as quickly or efficiently as healthy plants. Fusarium infects watermelons in the cool wetness of the spring when the plants are young. The additional stress from the heat and humidity of Southeastern summers make it difficult for growing watermelon plants to out-compete the pathogen. That’s when the wilting symptoms associated with the disease develop. Once symptomology is visible in the field, it can often be too late to control the disease. That makes early detection and action imperative to maintain yield potential.
Fusarium is a soilborne pathogen that moves from field to field on equipment. Management strategies require alteration as the pathogen develops new races. Previous tactics become less effective because the disease develops resistance to treatments. Growers and consultants must remain extra vigilant. Not only monitoring for disease presence, but also making sure management strategies remain effective.
Fighting Back
Most growers dealing with fusarium wilt in the Southeast are acutely aware which fields that have a history of disease presence. For them, soil fumigants and crop protectants are standard procedure. But in fields with no history of the disease, or where growers unknowingly inherit the issue, it can easily be mistaken for natural wilt from clogged drips.
“Soil fumigants provide the best depth to try and control and kill the spores that are there,” says Brock Ward, agronomy service representative at Syngenta. “The problem is that you can’t get them all. By the time the roots grow, Fusarium infests the plant and inhibits the root system from being able to take in the water and nutrients it needs, causing the wilt.”
Reliable crop scouts or consultants play a pivotal role combatting fusarium wilt. They notice small variations in the plant as early as 21 days after infection. Similarly, growers seeing wilting 21 days after planting should pull the plant from the field and send it to a university extension program for diagnosis.
“We’ve seen some success in the fight against Fusarium through soil fumigants used in succession with an in-furrow fungicide in the transplant water, followed by Miravis Prime fungicide over top,” says Ward. “That’s the most reliable form of control we have. But I’d strongly urge any grower to contact their retailer or trusted adviser to provide guidance on implementing a management plan early.”
[1] Rahman, M.Z.; Ahmad, K.; Bashir Kutawa, A.; Siddiqui, Y.; Saad, N.; Geok Hun, T.; Hata, E.M.; Hossain, M.I. Biology, Diversity, Detection and Management of Fusarium oxysporum f. sp. Niveum Causing Vascular Wilt Disease of Watermelon (Citrullus lanatus): A Review. Agronomy 2021, 11, 1310.
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