August is when soybean aphid pressure begins to shift rapidly. What appears manageable early can escalate within days, particularly as soybeans move through R1 to R3, when feeding pressure has the greatest potential to impact yield.
Conversations with growers around soybean aphid economic thresholds, consistent scouting and responsible insecticide use don’t just support good decisions. They shape how those decisions are made in-season and protect both yield and long-term control options.
When to spray for soybean aphids
Late-season soybean aphid management isn’t about calendar sprays. Recommendations should focus on staying disciplined, monitoring populations and advising action when the data support it. August is a critical scouting window, so make sure your growers are checking fields regularly to put themselves in a much better position to make the right call.
Guide growers to begin scouting in late June or early July, checking 20 to 30 randomly selected plants across several areas of each field.¹ Aphids tend to congregate at the top of the plant early but will move throughout the canopy and onto stems as populations grow. The standard recommended approach is to pull a plant from a random spot in the field and scan it thoroughly, counting aphids by tens or twenties when numbers are high.
Speed scouting is a practical alternative. The economic threshold for soybean aphid is 250 insects per plant, but growers don’t have to count them all. With speed scouting, they can flag plants as infected if they find at least 40 aphids present on a plant, then use a tracking tool to determine whether treatment is warranted. This recommendation can save growers time without sacrificing the integrity of the threshold-based decision. ²
Soybean aphid economic threshold
As mentioned above, the economic threshold for soybean aphid is 250 aphids per plant, with 80% of sampled plants infested and populations actively increasing. At that point, growers typically have five to seven days to schedule treatment before populations reach economically damaging levels.
You can help growers look beyond the raw count when making that call. If beneficial insects such as ladybugs, lacewings or flower bugs are present, or if there are many dark mummies that have been parasitized, populations may be held in check without intervention. If the majority of aphids are winged, the colony may be preparing to leave the field. Consistent scouting is what makes these distinctions visible.³
Recommending the right insecticides for soybean aphids
Spraying too early or overusing an insecticide can disrupt beneficial insect populations, trigger secondary pest pressure and contribute to resistance issues down the line.
Encourage growers to make product selection and timing decisions with careful consideration. Pyrethroids and organophosphates can provide reliable control, but results vary with temperature, canopy density and overall application quality.
Because aphids feed throughout the canopy and on the undersides of leaves, coverage is critical. Higher water volumes and adequate pressure help ensure the product reaches target areas, particularly in later growth stages when canopy density increases.
Guide growers toward labeled use, resistance management and post-application scouting. When recommended as a part of a threshold-based program, tools such as Sefina® Inscalis® insecticide and Renestra® insecticide can support consistent late-season control.
Late-season soybean aphid management comes down to timing, discipline and execution. Help reinforce the importance of threshold-based decisions and proper application practices to help growers protect yield while preserving long-term control options.
Experts are available to help you make your insecticide recommendations. Reach out to your seed retailer, a nearby extension office agent or a seed company professional like your regional BASF representative.
________________________________________________
Endnotes
- Ohnesorg, Wayne, and Thomas Hunt. On the Lookout for Soybean Aphids in 2025. University of Nebraska–Lincoln Extension CropWatch, 2 Aug. 2023, https://cropwatch.unl.edu/2023/soybean-aphid-scouting-and-management/.
- Ohnesorg and Hunt. On the Lookout for Soybean Aphids in 2025.
- Ohnesorg and Hunt. On the Lookout for Soybean Aphids in 2025.
