Hi — nice sentence! Here are clearer ways to say it:
Corrected (natural): The crows would be happy to try the new harvest if it weren't for the scarecrow.
Simple alternative: The crows would like to eat the new harvest, but they can't because of the scarecrow.
Why: We say "if it weren't for..." or "because of..." to show that the scarecrow is the reason the crows can't get the harvest.
Notes: Start the sentence with a capital letter. You can use "eat" instead of "try" here because crows would be eating the crops.
Great job — keep writing!