Weedwhacker said: What circumstances would cause the need to disinfect seeds? 
I would say each time when you can't be sure that seed producers disinfect them.
From Chat GPT:
There are several circumstances that may require seed disinfection, including:
Contamination with plant pathogens: Seeds can become contaminated with various plant pathogens such as bacteria, viruses, fungi, and nematodes that can cause plant diseases. Disinfecting the seeds can reduce or eliminate these pathogens and help ensure a healthy crop.
Protection from seedborne diseases: Some seedborne diseases can persist for a long time in the seed, making it difficult to control their spread. Disinfecting the seeds can help reduce the risk of seedborne diseases.
Preservation of seed viability: Seeds can become contaminated with microorganisms that can reduce their viability over time. Disinfecting the seeds can help preserve their viability and ensure good germination rates.
Compliance with regulations: In some countries, seed disinfection is required by law to ensure the quality and safety of seed stock.
In general, seed disinfection is used to promote healthy and productive crops, and to help reduce the risk of seedborne diseases and other plant health problems.
