It seems like it’s been a tougher season than normal for our tomatoes. First they got a late start because of the cold wet spring. Then we had a blast of heat just when they were blooming, causing the flowers to fall off. Now insects are attacking any tomatoes that have made it this far.
In one of my gardens, well over half of the tomatoes have tomato fruit worm damage. This is the same insect that bores into ears of sweet corn and other vegetables.
On tomatoes the damage shows up as holes or depressions that are clearly caused by something eating them. Tomatoes can look fine one day, then bam! holes in them the next. Often the worms tunnel into the fruit and leave behind “frass”, a polite term entomologists use for caterpillar poo.
The problem is you can’t find who doing the eating. At first you might suspect bird pecking or mice bites or even tomato horn worm damage. Tomato fruit worms are very hard to spot. I saw one today on a plant and by the time I retrieved my phone to take a picture for you it was gone, or at least I couldn’t find it again.
Holes chewed in the tomato fruit are a passageway for fungus to enter. Once the fungus takes hold, serious fruit rot sets in leaving nothing but a blob of mush hanging on the plant. When the holes are new, you can just cut away the damaged portion and still use the rest of the tomato.
About the only way you can control these critters once they find your garden is to spray an insecticide. I prefer to use the biological insecticide BT (Bacillus thuringiensis) because it will not harm pollinators. Since the tomato fruit worm is the larval stage of a moth (Lepodoptra) it is effectively controlled by BT. You still have to be a little careful using BT because it will kill any nearby butterfly caterpillars that come in contact with it. So spray only your target plants. Other insecticides will work too.
If you are seeing symptoms of tomato fruit worm on your tomatoes, I suggest getting them under control ASAP before they do any more damage.