We are in a period of high temperatures which will result in poor pollination, blossom drop or poor fruit set.  Day temperatures over 90F and night temperatures over 70F reduce fruit set.  In fact, three hours at 104F on two consecutive days will result in poor fruit set.  These temperatures may sound high, but if the tomatoes are grown in high tunnels without shade and outside temperatures are in the high 90’s it could be in the 100’s inside the tunnel.  Good air flow and shade cloth can help reduce the temperature.  The tunnel should have roll up sides and if possible, have the ends open.

Look at the joint just below the flower for a swollen yellow area followed by yellowing to the flower as an indicator of poor pollination.  At high temperatures applying a product to encourage pollination will not be beneficial.