Objectives : provide enough space between plants and potential sources of contamination to minimize the risk of contamination via water splash
What you need to know: The ground surface, even if it is covered with gravel or landscape fabric, is nearly impossible to maintain as a clean surface. The common practice of placing containers on the ground is generally not compatible with clean production.
6.3.1. Keep all plants on benches that will keep the bottom of plant pots are at least 2.5 ft above the underlying surface to minimize the risk of contamination via water splashed from the ground surface.
6.3.2. Bench tops should be made of expanded wire mesh or other open materials that do not allow water movement between pots and can be effectively sanitized. Plywood, wood pallets, or similar solid surfaces that allow water to pool or run laterally are not acceptable. Do not use benches that have wide horizontal surfaces that can catch and hold water or debris.
6.3.3. Wood is difficult to keep clean and to sanitize, so its use in nursery benches is generally discouraged. Wood is acceptable in applications such as upright members (bench legs) or other supports that do not catch soil, water, plant debris, etc.
6.3.4. Manage surfaces underneath benches and in walkways and driveways to prevent puddles, eliminate potential for splash, and remain free of weedy vegetation. Maintain adequate drainage and use gravel, landscape fabric, pavers, concrete, or other materials to keep underlying soil covered and avoid having exposed wet soil or mud.
6.3.5. Allow as much space as possible between benches and between blocks of plants within benches to minimize the potential for cross contamination via splash. Where it is not practical to provide a relatively safe gap of about 5 ft (1.5 m), consider using barriers (e.g., made of plastic film, or acrylic sheets) to separate adjacent blocks on a bench. Note that if contamination is detected, all plants within splash distance of a Phytophthora-infected plant or block of plants need to be quarantined for further testing or discarded, so maintaining separation helps localize spot infestations to the fewest plants possible.
6.3.6. Increase spacing between pots within blocks where possible to reduce the potential for pot-to-pot splash.