And now I'm pissed at myself because I picked it to cut it open to see inside and it was perfect inside. No critters of any kind. It was my biggest and first tomato. So what could this be?

Darn. Not sure, but looks like some kind of varment. Maybe a mouse, chipmunk, etc.. Do you have any small traps? I'd be tempted to aim one of my security cameras on it. Maybe someone else can be more specific on the critter than me. definitely looks eaten though. Do you spray with any bug spray like Sevin or something. The smell might deter them.

could be a bird pecking at them although the netting should deter them.

Whatever you do, do SOMETHING soon or you will probably lose every tomato.

Should I use tulle netting over it? We do have lots of chipmunks and squirrels round? Are they smart enough to go under the ends of the deer netting?

Forgive me if this doesnt apply in your case, but one year I was going crazy trying to figure out how those holes got in my tomatoes, and then one day i saw my darling, curious 2 year old son poking his fingers into them and cutting into them with his finger nails. Any chance this could be caused by a pest of the small human variety?

Looks like chipmunk or bird.

Here is a link that might be useful: Tomato Fruit Problems

Looks like Ecoterrorist (Squirrels)

I've read to try netting fruit trusses with repurposed produce netting bags from onions, avocados, oranges, etc. -- lightweight & easy to slip around them. Use a clothespin to close or tie a loose knot.

Bigfoot

Tulle might discourage the culprit unless it has sharp teeth and determination. A few weeks ago my wife made two large slip covers out of tulle to keep the birds off the blueberries. It worked like a charm in that case. Easy on/easy off. Like I said, try anything, and do it TODAY.

dickie....you must mean Littlefoot......lol ;-)

I wouldn't use any spray to deter this. Afterall you are going to eat the fruits soon. I use floating row covers and cut out a big 1 sqft piece and wrap it around each cluster of tomatoes. This is obviously tedious work if you have a lot of tomato plants but usually I only have to do this for the lower hanging fruits. This leads me to suspect my damage is done by critters and not birds.

If your damage is done by birds, they are probably just looking for water. Perhaps a waterbath might help in that case.

What if I spray a deterrent on the tulle and then drape the tulle over or around the plants? Will that work?

From my experience with birds and berry patches, you can't really deter birds by smell or taste. For rodents and critters, you can use repellent around the perimeter of the tomatoes. It works for my salad greens so I assume it will work for tomatoes as well. If you are using tulle over the plants, make sure you watch out for fungal disease because tulle will make it harder for the plants to dry off completely.

Oh my! My son just saw an animal inside my garden bed and a squirrel had gotten in and couldn't get out! Sonow I have to tie the deer netting tight to the wire mesh fence. This is the setup and although you can't tell inthe pic, the netting actually goes from the top of the bamboo to the ground overlapping the wire mesh. Those are some tenacious squirrels

{{gwi:83773}}

I have seen bird do this. If you have taken steps for prevention,and still persist I would get a small inexpensive game cam to find out, they are good for a number of things today1

You can actually see the bite marks in the one picture... I think it is squirrle or chipmunk or mouse.

Could also be a groundhog. They love to eat part of the fruit.

Cindy

I caught the squirrels in the act. They are picking my plants clean!