Nibbling the main stems
 

I am having some sort of difficulty with some of my tomato plants.
There's something nibbling on my main stem, right near the soil.
Can it be some insect or a type of worm destroying my plants?
Also, in any case, is there a cure?

Thx

Sounds like cutworms to me! They feed on stems above and below the soil surface.
I believe most people use cardboard or aluminum foil around the base of the plant to create a barrier.

How old are the plants and how big are the stems?

Cutworms will only chew on small, soft stems...like those of seedlings.

Mice, voles and such will chew on bigger stems.

Cutworrms,.. never knew about them.
I will try the cardboard/foil idea.
The plants are 2 1/2 months.
The stems are large now. There height are roughly four feet.
The problem started 1 1/2 ~ 2 feet (height).
I fenced the area (more secure) because of the cats roaming around my soil night time. The cats would usually dig and drop off there excess.
If it's mice nibbling, I have to get the cats again.
Mice can go through my fence no problem.
I have to investigate some more.

Thanks for everything everyone : )

Cheers