Q.Why Do Some of My Tomato Plants Become Hollow?
Why do some of my tomato plants become hollow? The plants are hollow and die.
it sounds like you have stem or stalk borers. "Stalk borer
Creamy-white to light purple larvae that eat tunnels in the stem, causing the plant to wither and die. Remove and destroy weeds where the insect may breed. Locate hole in stem where the borer entered, split stem lengthwise above the hole, and kill the borer. Bind the split stem, and keep the plant well watered. Spray to prevent further infestations." from this article: https://extension.missouri.edu/p/G6461