How could you gauge a grove owner’s crop?

From the text:

All Edgar's loans were based on Character, and Character was based on cash balance, worth of unencumbered real estate, ownership of bonds, and blue-chip stocks. Since Edgar was the only person in town who could, and did, maintain a mental index of all these variables, he considered himself the sole accurate judge of Character. It was said you could gauge a grove owner's crop by the way Edgar greeted him on Yulee Street. If Edgar shook his hand and chatted, then the man had just received a big price for his fruit. If Edgar spoke, cracked his face, and waved, the man was reasonably prosperous. If Edgar nodded but did not speak, nemotodes were in the citrus roots. If Edgar didn't see him, his grove had been destroyed in a freeze.