Liquid fertilizers, pesticides, fungicides, and herbicides should, in general, have the OMRI label if they…
Treated wood isn’t allowed for new construction where it will come into contact with the soil, though existing wood can be grandfathered in. If you’re looking for alternatives, you might consider naturally rot-resistant wood, such as cedar, black locust, black walnut, or white oak; materials like concrete, plastic or steel; or wood-plastic composites, as long as they do not contain fungicides.