2019 ASHS Annual Conference

Many growers use high tunnels to extend their growing season. In the fall however, crops are often planted during warm weather in high tunnels, subjecting them to heat stress early in development. Growers have employed shade cloth as well as fogging systems to reduce heat stress in fall-planted high tunnels. The present study evaluated the impact of shade cloth and a micro-fogging system on arugula (Eruca vesicaria), basil (Ocimum basilicum), and lettuce (Lactuca sativa) planted in September and early October in high tunnels in Athens, Georgia. While 30% shade cloth reduced day-time temperatures, it reduced yields in the October planted crops compared to non-shaded crops, suggesting that light levels were limiting at this time. The fogging systems did not significantly decrease average day time temperatures, but did increase soil moisture content and humidity. There were no significant effects of fogging system on yield of the crops grown. However, high humidity levels in the tunnels may have contributed to disease pressure due to basil downy mildew (Peronospora belbarhrii). Planting date also affected crop yields. October planted crops yielded lower than those planted in September, suggesting that the shade cloth and micro-fogging system were unnecessary in the cooler, shorter days, experienced later in the fall season.