Q. I have some Early Girl tomatoes that I planted in March from plantlets that I bought. I talked to the Early Girls about a month later and told them that if they did not flower in the following week, I would feed them to the worms in my compost pile. Well they seemed to have listened, because they made lots of flowers but the flowers didn’t set fruit. What did I do wrong?
A. Tomatoes are pollinated by insects, primarily bees. However, if temperatures are in the 90's and above they have trouble setting fruit. They just don’t like those high temperatures for pollination. They set better when temperatures are in the high 60's and 70's up to about 85F.
Other reasons for flower drop and no fruit set might be uneven watering so it is a good idea to mulch the plants. Straw is a good choice. I think a bale of straw no goes for about $8 locally. Low night temperatures below 55F can cause flower drop as well.
Also over fertilizing with nitrogen fertilizer may cause no flower development until the nitrogen is depleted a bit from the soil.
If temperatures are good, the bee does not actually have to visit the flower. Vibrations from bee activity are enough to set the fruit. If tomatoes are grown in greenhouses for instance and there are no insects in the house, the movement of the plants from vibrations caused by an electric toothbrush is often times enough to get them to set.
So make sure you have pollinator activity when temperatures are appropriate for fruit set. Otherwise, gently shake them while you are talking to them. Maybe a slight physical threat might work.