Pest Control · June 2025 · 5 min read
Aphids can multiply explosively in warm weather, reaching damaging populations within days. A balanced approach using scouting thresholds, biological control, and targeted sprays keeps populations in check without flaring secondary pests.
Scout fields at least twice per week during rapid growth stages, checking 30 or more plants per field on both upper and lower leaves. In soybeans, the economic threshold for soybean aphid is 250 aphids per plant with 80% of plants infested and populations increasing. For vegetables, treat when aphid colonies are found on more than 50% of plants and natural enemies are scarce.
Lady beetles, lacewings, and parasitic wasps are the most important natural enemies of aphids and can suppress populations without any chemical input. Avoid broad-spectrum insecticide applications early in the season that kill these beneficials. Planting insectary strips of alyssum, dill, or buckwheat near crop fields attracts and sustains beneficial insect populations throughout the growing season.
When thresholds are exceeded and beneficials cannot keep pace, apply a selective insecticide such as a Group 4C (sulfoxaflor) or Group 9C (flonicamid) that targets piercing-sucking insects with minimal impact on predators. Avoid pyrethroids when possible, as they tend to flare spider mites and kill beneficials. Time applications to avoid bloom periods when pollinators are active in the field.
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