2017 ASHS Annual Conference

The Lower Rio Grande Valley (LRGV) located in the southernmost part of Texas is one of the most productive vegetable areas in the State. However, growing vegetables in the subtropical climate of South Texas represents a real challenge due to harsh environmental conditions that limit production. Some of the limiting factors include high temperature, strong winds, and high pressure of endemic/new insects and diseases. Historical accounts implicate the demise of the once-flourishing tomato industry to outbreaks of virus diseases especially the tomato yellow leaf curl disease transmitted by whiteflies. Protected structures such as nethouses offer an alternative to open field production. Net-houses are relatively low-investment sealed structures thoroughly covered with insect net that provides a physical barrier that reduces pest pressure and wind damage effects. Eight cultivars including commercial available and Texas A&M developed hybrids were evaluated for production in nethouse and open field. Average daily temperature was similar between production systems. However, average temperature in open field was more variable, showing higher and lower peaks as compared to nethouse where temperature was more stable. Average solar radiation and wind speed was 5.6 MJ/Day and 6.4 km/h lower inside the nethouse as compared to open field. The average tomato yield was significantly higher when the same cultivars were grown under nethouse conditions (74,917 kg/ha) as compared to open field (47,474 kg/ha). This represents an average of ~60% increase in yield. In addition, the average fruit weight, uniformity and flavor components (brix and acidity) were higher when tomatoes were grown in high tunnels as compared to open field independently of the cultivar. The total percentage of fruit with defects was similar between nethouse and open field. However, the type of fruit defect varied between production systems. Fruit cracking was more frequent in nethouse while fruit zippering in open field grown tomatoes. Whitefly incidence was significantly lower under net-house, indicating that protected structures serve as a physical barrier to reduce disease pressure. Although thrips population were lower in nethouse as compared to open field, exclusion levels were not enough to prevent thrips population to reached high levels of infestation. Finally, production cost estimations indicate that production in protected structures is efficient, and it can be very competitive to supply the increasing demand of locally produced tomatoes.