Ukrainian sources give different thresholds for spider mites (Tetranychus urticae) on soybean — read each separately. The Vinnytsia oblast forecast (2025): 2–3 per trifoliate leaf with 10% of plants infested at flowering, 10 per trifoliate leaf at pod formation and fill. The trial methodology of the NAAS Institute of Plant Protection (Trybel et al., 2001): 2–3 motile mites per trifoliate leaf before flowering, 10 at pod formation and filling. Its authors (2022) call the common 3–5 motile mites per trifoliate leaf «actually very low». Above threshold, one acaricide pass (abamectin 0.5 L/ha or hexythiazox 0.3 L/ha) rescues 1.5–4 t/ha yield in heat-stressed droughty years common in eastern oblasts. Lower-than-threshold populations self-regulate via predatory mites (Phytoseiulus) if you haven't wiped them out with broad-spectrum insecticide earlier. Scout weekly in hot, dry conditions when risk is highest.