Which Synthetic Substances Are Allowed in Organic Crop Production?

1What § 205.601 actually says

The section opens with two binding conditions before it lists a single substance:

Two rules fall out of that chapeau:

1. No contamination — even a listed synthetic isn't allowed in a way that contaminates crops, soil, or water.
2. Last resort for pest control — insecticides, herbicides, disease controls, and the like may only be used after the preventive practices of §205.206(a)–(d) — rotation, sanitation, habitat, mechanical/physical controls — prove insufficient. Your certifier will expect your OSP and records to show that sequence, not just the spray log.

2How the list is organized — the use category is part of the rule

§205.601 is organized into use categories (a) through (o): algicides/disinfectants/sanitizers, herbicides, compost feedstocks, animal repellents, insecticides, insect management, rodenticides, slug/snail bait, disease control, crop and soil amendments, plant growth regulators, floating agents, synthetic inert ingredients, seed preparations, and production aids. A substance is allowed only under the category where it appears. The same substance can appear in several categories with different annotations — copper sulfate, for example, is listed separately as an algicide in rice systems, as tadpole-shrimp control in rice, and as disease control, each with its own restriction.

3The annotations are binding — examples from the list

The em-dash text after a substance is not advice; it's the legal limit of the allowance. A few high-demand examples, quoted from the list:

• Fixed coppers (disease control): "Coppers, fixed—copper hydroxide, copper oxide, copper oxychloride, includes products exempted from EPA tolerance, Provided, That, copper-based materials must be used in a manner that minimizes accumulation in the soil and shall not be used as herbicides."
• Horticultural oils (insecticide): "Oils, horticultural—narrow range oils as dormant, suffocating, and summer oils."
• Insecticidal soaps: "Soaps, insecticidal." — one of the few with no annotation.
• Micronutrients (soil amendment): "Micronutrients—not to be used as a defoliant, herbicide, or desiccant. Those made from nitrates or chlorides are not allowed. Micronutrient deficiency must be documented by soil or tissue testing or other documented and verifiable method as approved by the certifying agent." — note the documentation requirement written into the substance listing itself.
• Elemental sulfur appears as insecticide, slug/snail bait, disease control, and soil amendment — an example of a substance allowed across several categories.

4The list changes — check the current text

The National List is amended through federal rulemaking on an ongoing basis (sunset reviews, petitions, NOSB recommendations). A substance that's allowed today can be removed, re-annotated, or restricted. That's why this page tells you the logic and points you at the current official text1 rather than promising a frozen list — and why the review date at the bottom of this page matters more here than on any other explainer.

5Substance vs product — the step people skip

§205.601 allows substances. The jug on the shelf is a product — active ingredient plus inerts, and the inerts have their own rule (§205.601(m)). A brand-name product needs to comply as formulated; an OMRI listing is the common evidence certifiers accept. Then your certifier still has to approve the input on your OSP.

6How to document this on your farm

For every §205.601 input, your records need to show: the exact product used, where and when, the target pest or need, and — for pest-control uses — that preventive practices came first. OrganicAssistant logs inputs as you use them, runs each against the OMRI/National-List check, and keeps the "we tried prevention first" story connected to your OSP's pest-management plan, so inspection day is a lookup, not a reconstruction.

7The bottom line

§205.601 is a list of narrow permissions, not a menu of organic-approved sprays. Check the substance, the use category, the annotation, and the prevention-first requirement — then verify the specific product and clear it with your certifier before it touches the field.

This explainer summarizes federal regulation in plain language; it is not legal advice or a compliance determination. Your certifier makes the final call on your operation. Reviewed against the eCFR text of 7 CFR § 205.601 current as of 2026-07-02.