Question:
I have some tomatoes that haven't ripened yet and have these brown scars on the bottom and this one also had some large bites out of the other side. I've been spraying the tomatoes with a bit of cedar oil diluted with water in the mornings but no other things.
Do you know what might be causing this and the bites? Not sure if it's two separate problems or from the same thing.
Master Gardener response:
There a couple of possibilities for the damage shown in your very helpful picture. One is the early onset of tomato blossom end rot about which you can read more here: https://ipm.ucanr.edu/PMG/GARDEN/VEGES/ENVIRON/blossomendrot.html. You'll know more as the fruit matures and becomes brown and shrinks. I suggest that you sacrifice one of your damaged unripe fruits and look inside to see if there are signs of fruit rot.
More likely, I think, is caterpillar damage. That also would explain the bites you describe. Caterpillars are nocturnal feeders so I suggest that you take your trusty flashlight out to your tomato garden after dusk or very early in the morning and inspect your plants and fruit. Also, look for black dropping on lower leaves and fruit (you can do this in the daytime) and you'll have a good indication that caterpillars are the culprits. Tomato hornworms https://ipm.ucanr.edu/home-and-landscape/hornworms/#gsc.tab=0 get really big really fast and can be quite startling if you're not expecting them, BTW.
If caterpillars are the problem you can apply a naturally-occurring bacteria called Bacillus thuringiensis (Bt) according to package directions. It's available at garden centers, big box stores and on-line. Be sure to spray the soil as well as the plant because the caterpillars will go to ground during the daytime.