One of the Hubbard squash started to brown. Not blossom end rot. Three other fruit on the vine are large and healthy as are the leaves. See photo. Cause and solution, please. Ray R
Could be poor weather conditions at fertilization, incomplete pollination, too much fruits per plant (then it will reject some) or some fungal disease, like Gummy Stem Blight/Black Rot, Anthracnose or something similar.
Thank you. The fruit was larger than my fist when it started to show brown patches so I doubt that it is fertilization caused. I don't know Gummy Stem Blight and will check. Ray R
Sometimes my watermelons fail with the similar symptoms even when they are at the size of a golf ball. Usually, when there is already larger fruit on the same vine. This could be self regulation of fruit bearing ability. Or there is too warm/cold for proper fruit development. Your plant seems to have healthy leaves and stem, therefore I'd suspected some disease as the last option.