2018 ASHS Annual Conference

Colored bell peppers provide an opportunity for vegetable growers to receive a price premium over un-ripened, green bell peppers. Utilizing high tunnels to produce colored bell peppers increases fruit quality and ripening speed. While there are benefits to high tunnel pepper production, high heat can lead to plant stress, blossom drop, sunscald and reduced marketable yields. The objective of this study was to identify colored bell pepper cultivars that perform well within high tunnels and test shade cloth treatments as a means to mitigate heat stress and improve yield and fruit quality. This study took place in six 4.5 m × 10.7 m single-poly passively ventilated quonset high tunnels during 2017 in central Iowa. Shade cloth treatments were 30% and 50% light-reducing, black woven shade cloth compared to a no-shade control applied to individual tunnels in two replications. Within each tunnel (shade treatment), seven bell pepper cultivars were planted in replicates of three. Cultivars included Archimedes, Delirio, Flavorburst, Red Knight, Sirius, and Tequila. Data was collected on plant growth characteristics (SPAD, plant height, leaf area, and biomass), marketable and non-marketable yield, and fruit quality (soluble solids, titratable acids, fruit shape, and lobe number). Environmental parameters (PAR, soil and air temperature) were monitored throughout the growing season. Mature fruit was harvested fifteen times between 5 July and 11 October. As expected the use of a shade cloth reduced the incidence of sunscald from 4.7% to 1.9%. Sirius had the highest incidence of sunscald (4.4%) and Tequila had the lowest incidence (1.0%). Marketable yield was 1.6 kg for the control compared to 1.2 and 1.1 kg for 30% and 50% shade cloth; however, the mean percentage of marketable fruit ranged from 64.3% (30% shade cloth) to 66.8% (50% shade cloth). When considering cultivar, the percentage of marketable fruit ranged from 55.3% (Tequila) to 75.1% (Red Knight). Dry shoot biomass was lowest for plants grown under the 30% shade cloth (92.4 g) compared to 50% shade cloth (93.1) and the control (102.5 g). Our data shows that the use of a shade cloth holds promise for reducing losses in fruit marketability of colored bell peppers, but research should continue to optimize the production of colored bell peppers within Midwest high tunnels.