I have two large tomato and two cherry tomato plants.

On my large tomatoes that have began to ripen i went out and saw on the top quarter a perfect circle tha been chewed away. The next few day this eaten portion has increased and half of the tomato has been eaten away almost pefectly as if cut with a knife. Today, I noticed also on anther tomato beginning to ripen the same thing is happening a quarter of this tomatoe on the top of the vine a perfect quarter has dissappeared.

I've noticed when i go out in the monring to water on the eaten toamtoes, it looks like little fruit flies. Are these the cause of eating the tomato? If so, how can I protect the rest of my crop?

Nothing has been done to the cherry tomatoes.