Shading Nets Reduce Heat Stress and Incidence of Phytophthora Blight (Caused by Phytophthora capsici) and Fruit Yield in Bell Pepper (Capsicum annum L.)

High temperatures during late spring and early summer cause flower drop, fruit abortion, and fruit physiological disorders such as sunscald, resulting in substantial fruit yield loss to bell pepper (Capsicum annum L.) in the southeast U.S.  Shade nets are used to modify the microenvironment with the goal of improving crop production.  The objectives were to evaluate effects of shade level on plant disease and fruit yield. Experiments were conducted in Tifton, GA, during the spring and summer 2009 and 2010, with cvs. Camelot, Lafayette, Sirius, and Stiletto.  Bell pepper plants were grown on plastic film mulch under shade levels of: 0% (unshaded, as a control), 30%, 47%, 63% and 80%.  Incidence of Phytophthora blight (caused by Phytophthora capsici Leon.) and fruit sunscald decreased with shade levelin both 2009 and 2010.  Total and marketable (Fancy and US1) fruit yield, and individual fruit weight increased with shade level to a maximum and then decreased with further increases in shade level. US2 and cull (sunscald) fruit declined with increasing shade level.  Based on regression analysis, optimal shade level for marketable yield was 34% and 35% for mature green and ripe fruit, respectively.  Among cultivars, ‘Camelot’ had among the highest marketable fruit number and fruit yields and ‘Sirius’ the greatest number of cull fruit. ‘Sirius’ produced the heaviest fruit, followed by ‘Camelot’, ‘Lafayette’ and ‘Stiletto’.