It's lurking in your soybean fields waiting for the right conditions to kill soybean plants. The "it" is Sudden Death Syndrome (SDS) in soybeans. "SDS is common in most soybean growing areas, particularly in the Corn Belt," says Scott Dickey, Beck's Hybrids Field Agronomist for Western Missouri.
SDS is caused by a species of fusarium fungus that lives in crop residue. The disease thrives in continuous soybean fields but can survive through a corn rotation to attack soybeans the following year if conditions are favorable for infection. SDS flourishes in cool, wet soils early in the soybean growing season.
The fusarium enters the soybean plant through infection sites in the roots. "Harsh soil conditions, such as waterlogged and compacted soils, can damage roots creating infection sites," says Dickey. "That's why SDS is more prevalent in wetter areas of fields, often showing up in low-lying patches."
It's also more common in fields with high soybean cyst nematode (SCN) pressure because nematodes feeding on roots open infection sites for the SDS-causing fusarium to enter.
SDS can infect soybean plants as early as 2 to 3 weeks after planting. However, disease symptoms usually don't show up until plants move into heavy pod load later in the season. It's then, after flowering, that leaves start dying and falling off the petioles. "By the time the signs of SDS show, it's too late to do anything to reduce losses," says Dickey. "You can manage against SDS losses," he adds, "but it must be done before planting."
TACTICS TO TACKLE SDS
Dickey recommends a multifaceted approach incorporating as many of the following management practices as possible on fields with a history of SDS:
> Plant soybean seed with SDS tolerance: "The benefit can be significant," says Dickey. Varieties with good tolerance for SDS are available in all soybean maturities.
> Seed treatment: Dickey recommends Beck's Escalate Nemasect for cyst nematode control.
> SDS+ seed treatment to control SDS. "Escalate Nemasect SDS+ works in several ways to control SDS," he explains. "It includes a hard-chemistry fungicide, a bio-fungicide and a bio-stimulant which, when combined, provide good protection against SDS. The seed treatment protects against nematodes, too, which may help reduce SDS problems."
> Improve drainage: SDS is more prevalent in soils that remain wet from poor drainage or compaction. "Improving drainage reduces soybean root damage and improves overall plant health," says Dickey.
Two other management practices to help control SDS are: (1) reduce plant residue in the soil and (2) later planting. "While these will help control SDS, both come with downsides," says Dickey. "I'm reluctant to give a blanket recommendation to increase tillage, but there may be situations where reducing residue via tillage may help. Farmers need to find a balance and manage fields individually when fighting this disease."
Later planting tends to avoid the cold soils that favor the SDS-causing fungus. It's counter to other research showing yield benefits for early-planted soybeans, notes Dickey. That research includes a 2018 Beck's Practical Farm Research (PFR) study in Missouri comparing soybean yields for planting dates ranging from April 21 to June 15. The study found that after May 12, the later the planting date the lower the yield potential.
New control tools give growers the opportunity to adjust their SDS management program, notes Dickey. "The development of effective SDS seed treatments gives growers the flexibility to plant earlier for higher yields and the opportunity to reduce the use of delayed planting to manage SDS."
You can hear more about SDS by listening to the Practical Research Drives Profitable Performance podcast at: https://spotlights.dtnpf.com/…
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