Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
In tomatoes I am seeing reduced fruit set with few fruit on some flower clusters. In Figure 1 there was the possibility of nine tomato fruit developing on these two clusters, but only one third of that made it to viable fruit. This has to do with poor pollination and fertilization of the tomato flowers due to heat or other stresses (disease, field flooding, insect feeding damage, poor plant fertilization, etc.). Not much can be done about it now other than to keep the plant well-watered and free of foliar disease. If the flower/fruit abortion is severe, as it is in some cultivars, something that can be done earlier in July or late June is to use a 30% shade cloth over the tomato plants (Fig. 2). Using shade cloth after the first fruit clusters form can increase marketable yields by 30-50% depending on the season and cultivar.
Figure 1. Two fruit clusters with only 3 out of a possible 9 fruit developing.
Figure 2. Shade cloth over some tomatoes