Is it true that in Eretz Yisroel, if a bag of flour is left unopened in a cabinet, it would be suspected of infestation?
What about in the USA? If there is a bag of flour in a low kitchen cabinet, that was not sealed after opening (or was totally opened), is it a problem to use the flour?
According to a kashrus professional in Eretz Yisroel, flour that was left in a cabinet is only problematic 2 months after the expiration date (this applies even if it is in a vacuum packed bag), or if there is a known infestation problem in the kitchen.
The above applies to Israel.
Regarding the United States, I am not familiar, however here is a quote from the CRC
“Although not required, it is always a good idea to check a sample of flour from a bag before using. The best place to store flour is in the freezer. The longer flour is kept out of the freezer the greater the chance that insect eggs in the flour can hatch. This is especially true if the weather is warm and humid. It isn’t possible to give an exact time frame as to at what point one would be strictly obligated to check all the flour before using, as we don’t know how long and in what conditions the flour was stored before it came to your house”.