What is the interval for delimitation laboratory testing after a positive nematode find?

The correct choice indicates that a 20x20 ft grid interval over a quarter-acre is the appropriate response after a positive nematode find. This method allows for systematic and efficient sampling in a designated area. By employing a 20x20 ft grid, you can cover a substantial area while still maintaining precision in identifying potential hotspots of nematodes, which are critical for managing plant health and soil quality.

Using this grid size strikes an effective balance between comprehensive coverage and the practicality of testing. It ensures that the testing process provides robust data to inform any necessary follow-up actions, such as soil treatment or crop rotation strategies, to mitigate the positive finding.

In contrast, other options either involve grids that are too large, compromising the detail needed for effective testing, or too small, resulting in unnecessary redundancy and resource expenditure. Thus, the interval represented by the correct answer is designed to optimize both the accuracy and efficiency of nematode management efforts.