Some interesting research work from Jerry Brust, UME Vegetable IPM Specialist
(re-printed from article by Jerry in the UDEL Weekly Crop Update- Aug. 26, 2016)
I have been experimenting with using shade cloth in tomato over the last 5 years and they have worked remarkably well in increasing the marketable yields of many different cultivars of tomatoes by 20-50%. I use a 30% filtering shade (using any more than 30% tends to reduce yields and size of tomato fruit). The shade cloth is draped over the top of the tomato stakes and held down at both ends (Figure 4). I know this does not seem practical, but only the top ¼ of the plant needs to be covered (not shown) which means a grower could use shade cloth with a 4 ft width and as long as they wanted it to be. The shades can be used over and over for many years; the ones I am using have been in use now for 5 years. The shade cloth helps tomato plants come through very stressful weather conditions, i.e., high temperatures with high dew points and even heavy rains in much better shape than plants that were not covered.
Figure 4. Shade cloth over a section of tomato row