Fungus Gnats on Indoor Seedlings: Organic Control Options

Black gnats infesting indoor seedling greenhouses are likely fungus gnats. Their larvae feed on organic matter and roots in overly moist soil. Insecticidal soap may not suffice for heavy infestations.

Organic Treatment Options

When soap fails, escalate to botanical insecticides:

• Pyrethrum – derived from chrysanthemum flowers, fast-acting, low toxicity.
• Rotenone – plant-based, effective against a wide range of insects.

Both break down quickly in soil with no harmful residues. Apply as directed during active insect periods. Sources include:

• Gardens Alive – Pyrethrum
• Gardens Alive – Rotenone
• Planet Natural – Pyrethrum Powder

Reduce soil moisture and improve air circulation to prevent recurrence.