I was out at our CSA farm this morning digging potatoes and picking tomatoes (yes it was 90 degrees and we were in full sun! not as much fun as some times). They were growing Brandywine, German Johnson, and some kind of red pear shaped tomato I didn't get the name of, all heirlooms.
At a rough estimate 1 in 5 or so had to be pitched because of BER, we were picking them blushed not ripe to try to prevent them cracking, but a number were cracked already (except the red pears seemed to be much more crack-resistant). Some of them had to be pitched because they had been munched by a a big brownish stripey worm (not a hornworm). I saw a few of the worms, so I know. Saw one hornworm, but it had the white eggs all over its back, like Applestar's picture, so I left that alone. (Before I started hanging out here, I wouldn't have known what that was! )
Came home and picked 17 tomatoes off my 5 plants. None had BER, which I have never seen on one of my tomatoes in any of the years I have grown them. Only a couple were showing any signs of cracking, and none had any worms etc. Mostly perfect.
Farm is 1/2 hr away, same climate, similar soil. They and I both grow organically. So what makes the difference? Two things I can think of ... they are growing all heirlooms and I am growing all hybrids. And since I am growing on such a micro scale, I can pay more attention to them, especially watering! I don't think the CSA farm irrigates at all and we've had very little rain. They are outside the city and have had a little more than me, but still not nearly enough in this heat. Consistent watering instead of depending on rain, helps prevent the BER and the cracking and may give the plants more resistance to attack.