Isolation distances are part of the seed standards developed to preserve the integrity of a specific variety. The terminology and calculations used to determine isolation zones for a field and whether border removal flags are required can be confusing. Below are general definitions and a few helpful tools to guide you through this topic. For specific isolation requirements for seedstocks or non-wind pollinated grasses, be sure to check the species standard.
Isolation: the distance requirement between a certified field and another field of the same species, or potential cross-pollinator. If the adjacent field is the same variety or different ploidy and also certified, no isolation is required. The certified class requirement for most species is 165 feet from field edge to field edge.
Isolation zone: the acreage of a certified field within isolation. Calculate it by multiplying the length of common border, by the isolation requirement minus the distance between field edges. All field borders within the isolation distance must be included in the total. Calculate your isolation zone.
10% rule: if the isolation zone acreage is 10% or less than the total field acreage, no isolation is required. Remember, the isolation zone is the sum of all sides adjacent to contaminating pollen.
Border removal: when the isolation zone is over 10% of the total field acreage, isolation is required and you may implement border removal. Stakes or flags are placed at a specific distance within the certified field to indicate that they will not be included with the remainder of the field at harvest. Grass in within this border must remain standing to serve as a buffer to absorb pollen flow from the adjacent field, and then taken as uncertified. In most cases, border removal flags are placed at 90 feet from the contaminating field edge. Check your border removal situation.
Is your field at or less than 90 feet from the other field? Border removal may still be required. Check out this graph.
Border removal flagging: obvious stakes or flags for border removal should be clearly marked every 300 feet and above the canopy, and visible at the time of crop inspection. The bigger and brighter your staking or flagging can be, the better. Wire flags are very hard to see and may be cause for reinspection.
Mechanical border: in situations where a mechanical border is required to prevent mixing, the distance is 15 feet. This area may be mowed or flagged, but must be visible at crop inspection.