Training of Growers and Extension Agents in the Dominican Republic on Managing Heat Stress of Bell Pepper (Capsicum annum L.) Grown in High Tunnels

The Dominican Republic is located in the Hispaniola Island in the Caribbean region. Its climate differs substantially over short distances and is the most diverse of the Caribbean. Annual average temperature is 25 degrees C, ranging from 18 degrees C (at higher elevations) to 28 degrees C (at sea level). Average annual rainfall is 1500 mm. Although sugar, coffee, cocoa, and tobacco are the principal cash crops of the country, peppers are increasing in popularity on the country's exportation market. Bell peppers grown in high tunnels and greenhouses may be impacted by high temperatures that result in reduced fruit yield and quality. In this article, we make a short review of cooling techniques for high tunnels and share the experience of training bell pepper growers and extension personnel from the Dominican Republic regions of San Jose de Ocoa and Constanza on how to manage heat stress of bell peppers grown inside high tunnels. Bell pepper plants inside high tunnels showed symptoms of heat stress, including reduced plant and fruit size, small fruit number, and a mild leaf chlorosis. In both regions, but particularly in the warmer region, San Jose Ocoa, because of occurrences of high temperatures inside the high tunnels, growers were advised to use well-ventilated high tunnels, such as structures with plastic film on the top and screen net on the sides. Other strategies such as shade nets (30% to 40% shade) placed on top of the high tunnel or whitewash paint applied on the high tunnel cover may also help reduce air and soil temperatures inside the tunnel. Use of white or silver reflective mulch, instead of the commonly used black mulch, may provide additional reduction of soil temperature. In conclusion, high tunnel structures developed for temperate regions, with limited to poor ventilation, may result in excessively high temperatures inside the high tunnels and thus were not recommended for the Dominican Republic regions of this study. More research is necessary on adequate high tunnel design and cooling techniques for high tunnel production, particularly in tropical regions.