Hi Amanda. I'm thinking not to the borer... it looks like mechanical damage to me. Maybe the weight of the vine caused the split. If it is a borer, you will know. The plant will look great, happy and healthy, then one day you go out and the whole plant has collapsed. I almost always get them here. The solution is to cover up the plant at the time the moth lays the eggs that becomes the caterpillar borer, thats usually before it blooms, so don't worry about the plant being pollinated.... check out articles on the web for more info. Borers infect squash plants, too.