Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Plant Sciences

Major Professor

Carl E. Sams

Committee Members

Dennis E. Deyton, Dean A. Kopsell


Tomatoes (Solanum lycopersicum) are the most commonly grown greenhouse vegetable crop, preferred for their high consumer demand and high value. To improve profitability, growers continuously seek new techniques to improve yield and cost efficiency of production. Four studies were conducted between Fall 2008 and Spring 2010 in greenhouses at the University of Tennessee Plateau Research and Education Center (35°56́ N lat.) and the University of Tennessee (35o 57’38” N lat.) to investigate the impact different plant spacings (12, 16, 20, 24, or 28 inches in-row), pruning systems (one leader versus two leaders), cluster thinning (three, four, five, or six fruit/cluster or not thinned at all), and pest control practices (chemical versus biological aided by banker plants) had on yield and fruit size of hydroponically grown ‘Trust’ tomatoes. A cost analysis was performed to compare one leader versus two leader pruning systems and pest control regimes by chemical versus biological methods. A plant spacing of 28 inches resulted in significantly more tomato fruit per plant than the 12 inch plant spacing. However, yield per area (lb/ft2) decreased with wider plant spacings. Pruning two tomato plants to one leader increased total yield and was more economical in the fall; whereas, in the spring the double leader production system did not affect yield but was more economical. For fall production, thinning to three or four fruit/cluster resulted in more jumbo tomatoes than the control or treatments thinned to five or six fruit/cluster. Total marketable yield was greater when plants were not thinned or thinned to six fruit/cluster, but average fruit weight decreased. For spring production, cluster thinning did not affect marketable yield, percentage of culls, or fruit weight. Chemical pest control and biological pest control had comparable effects on whitefly (Trialeurodes vaporariorum) pest populations without affecting yield. However, biocontrol methods were more expensive. Marigold banker plants were successful in Orius reproduction, but thrips (Frankliniella occidentalis) populations were not affected by the presence of banker plants. Data from these studies demonstrate the ability to improve production and profitability of greenhouse tomato systems through simple changes to cultural management techniques.

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