Your Plant Health map may be as detailed as a few centimeters per pixel. Management zones make the highly detailed agricultural maps into more manageable datasets by grouping similar regions (either geographically or visually) within a field. Categorizing your area of interest according to a range of values can lead to better understanding of overall crop health. More details here: Zone Management.
Once you have defined the zones or grid you want, you can then export your data. More details in this Displaying SHP Plant Health Data article.