Something similar happened to my zucchini plant. Half the plant is gone, eaten through at the base. I will look closely to see what varmint is guilty and post. Two large zucchini fruits were eaten in half and rotting, also.

It is ants! Ugh! I think my zucchini plant is destroyed. Even the new flowers are eaten off.

I had that problem with two sunflowers although they were not in the stem they were under the leaves I literally used half of a can of Raid Earthblends Multi-Bug killer on those two flowers , I soaked the plants including the base soil around the plants ...they were 41 inches tall at that time they recovered and now are 55 inches tall .I was sure that much Raid would have killed the sunflowers but they are doing okay now so Raid actually works and is not necessarily a death sentence for plant as well as insect . It is possible that aphids were attacking the leaves and the ants were attacking the aphids but what tipped me off was the dark shadows moving around on the sunflower leaves in the midday sun . Unfortunately I don't think you can get rid of ants they are everywhere just keep your eyes open and deal with the ants as they come usually they leave things alone . I would honestly say it is hard to tell whether the ants are the culprit or another insect which the ants were tryng to deal with . I'm not a garden pro or insect pro but ants do play a role in this war zone of insects in our gardens ...I started my zuchini indoors and let them outside for 1 day in april (3A zoning)because it was warm out , when I brought it in , it passed whatever disease it picked up to the other zuchini without infecting any other plants and they all died a horrible death ...the stems were hollow and when gently squeezed the stems would pop and squirt clear fluid everywhere . I thought that it was maybe a little too cool outside for the plant and it froze but since it passed the problem to the other zuchini I realize it was a stem boring insect (that may or may not be ants but it certainly was a stem borer) . Good luck with the zuchini ...personally after that event I gave up on trying to grow zuchini I just didn't trust myself as a rookie gardener.

I had this same problem with my pumpkin plants last year, I was hoping it was just a fluke and tried moving the plant around more (it was in a pot)

but the ants kept attacking it, they weren't even harvesting the little green pumpkins, they were just cutting them off the vine and leaving them hanging dead.

they were also eating away at the base of the vines as talked about here..

I mean.. what the heck do these ants have against squash plants? they aren't attacking them for food. it's like they have some sort of hatred for the plant itself.

I have tried bug sprays such as raid, but to no avail they just keep coming, whatever is driving these ant attacks is something they refuse to give up..

I read that ants hate cucumbers. I cut up some cucumbers and placed them around the garden bed. I don't think it kills them, but it will keep them away from the plant, or the area where the cucumber is. Try mixing some in the soil around your plants.

happened to me

Pretty much all my vining vegetables get this kind of damage. The stem splits open for several inches. The plant dies below the split. I was told it was probably cutworms, but it doesn't look anything like what is shown in a Google search. For reference, we're talking about the coast (7 or 8 miles back) of South Carolina.

As a means of payback, I bicarbonate of soda-ed their nests, two of them. Pretty soon, they had drilled a hole through, and were continuing business as usual