What causes a zucchini fruit to rot or liquefy on the inside? I have a very large zucchini plant that has been producing fruit. Lately I have found mushy/gooey spot on the stem and I had picked a fruit that had gotten a little larger than what I normally let them get. I left the fruit outside for a few hours, when I went to pick it up, the fruit squirted out a watery substance and was squishy feeling. I split the zucchini fruit open and the whole inside was gooey and liquefied. The outside of the zucchini fruit looked normal.
Zucchini Fruit Gooey and Liquefied
Certified GKH Gardening Expert
This could be a couple of different issues.
Vine Borer, Belly Rot or Blossom End Rot.
Here are links that have more information and with a closer examination of you plant you may be able to pinpoint the cause.