I received this information when we crossed the border at Sweetwater, Montana this summer. It is a good summary of what the U.S. customs is watching. I have not found any similar listing for crossing into Canada, but I can imagine the list would be similar.
Most people know about the restrictions on Guns, Alcohol, Tobacco and Marijuana. There are a lot of other restrictions on food products, souvenirs, and even musical instruments.
Meat:
Beef, Lamb, Pork, Goat and Seafood is allowed for personal use.
Poultry and eggs must be fully cooked or canned. No fresh poultry
Deer, Caribou and Moose with a hunting license and import permit is allowed, must be butchered by commercial processor
Pet food:
Must be in the original container. It can be opened if the pet is present. Raw pet food requires CFIA export certificate
Grains:
Rice, Soybeans, Chickpeas and Safflower seeds are prohibited from all middle eastern countries. Should be stored in the original container with country of origin clearly marked.
Firewood:
Firewood must have a heat treatment certificate
Fresh Fruit:
All citrus is prohibited.
Avocados with the seed or peal are prohibited
Fresh cherries are prohibited from Ontario
Bananas are allowed
Melons (cantaloupe, watermelon, and honeydew) are allowed
All other nuts and vegetables must contain packaging displaying the country of origin.
Honey is limited to 20 lbs. before special import certification is required.
Vegetables:
Corn-on-the-cob is unclear.
Potatoes must be free of soil and commercially packaged. Limit of 50 lbs. Home grown potatoes are prohibited.
Onions, leaks and/or chives are prohibited
All other root crops must be clean and free of soil.
Tomatoes and peppers are prohibited.
Plants:
All plants including houseplants, bedding plants and trees must have a Phytosanitary Certificate issued by the CFIA.
Seeds must have a Seed Analysis Certificate or Phytosanitary Certificate issued by the CFIA.
More detailed information is available at:
https://www.aphis.usda.gov/aphis/res...er/intl-travel