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Richard G. Snyder

Production of greenhouse tomatoes, while not new to Mississippi, has increased in the past 4 years to an industry of noteworthy size. This specialized industry in Mississippi has faded in and out of popularity over the years, as new growers have sometimes been stimulated by greenhouse supply companies looking for prospective customers. Often, rumors of incredibly high yields, consistently high demand and price, and minimal problems with pests and culture have encouraged novice growers to start in such a big way as to make it impossible to pay off their debts.

With strong support from the Extension Service and the Experiment Station in Missiippi, the number of grown has increased from a handful to 71, utilizing 224 free-standing or gutter-connected greenhouse bays, occupying 12 acres under plastic. This has placed Mississippi within the top 10 greenhouse vegetable producing states in the U.S. and has helped to build a $1.8 million industry. University support has taken the form of: 1) monthly Vegetable Press Newsletter, 2) annual Greenhouse Tomato Short Course each April, 3) Greenhouse Tomato Handbook (1992). 4) organized Greenhouse Tours. 5) a greenhouse tomato production video now in the planning stage, and 6) excellent support by Plant Pathologists and Entomologists.

To support these growers, most of whom are new to greenhouse tomatoes, a number of culturally based experiments have been performed at the Truck Crop Branch Experiment Station. These have included evaluation of heating systems, media, varieties, biological control, fog cooling, and bumblebee pollination.

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Richard G. Snyder

The greenhouse-tomatoes list was created to provide a method for commercial greenhouse tomato growers to communicate with each other to learn from others' experiences. Its purpose is to connect growers with vendors of greenhouses, fertilizers, seeds, and other supplies, and to facilitate networking among growers, agents, specialists, and researchers. The goal of the greenhouse-tomatoes list is to develop high quality discussion that benefits commercial growers and the entire greenhouse tomato industry. This is accomplished by promoting the list to growers; keeping the list small so that the traffic is manageable; avoiding promotion to hobbyists so the list does not become cluttered; avoiding SPAM. Excellent majordomo software has been 100% effective in the latter. The list was first offered to growers at the 2004 Greenhouse Tomato Short Course (GHSC) in Jackson, Miss. Then, it was promoted through other e-lists for vegetable specialists, new crops, greenhouse growers, hydroponics, etc. The final phase was to promote it at various grower meetings around the U.S., through trade magazines, and at the 2005 GHSC. Currently, the list consists of 141 members. Subscribers are from the U.S., Argentina, Australia, Canada, England, Germany, Newfoundland, Pakistan, Romania, South Africa, Virgin Islands, and Thailand. Demographics are 31% university, 15% suppliers, 34% growers, 20% unknown. The greenhouse-tomatoes list is housed on a server at Mississippi State University with nearly all functions handled seamlessly by majordomo software. To subscribe: send e-mail to majordomo@lists.msstate.edu with the following message: subscribe greenhouse-tomatoes. You will get a confirmation email telling you that you must reply. You must be subscribed to send anything to the list. Once subscribed, to communicate with the whole group, address an email message to greenhouse-tomatoes@lists.msstate.edu and everybody on the list will receive it. To make this easy, the user can save that address to a nickname, such as ght or greenhouselist. More information can be found at http://www.greenhousetomatosc.com.

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Richard G. Snyder

Successful greenhouse tomato businesses are able to keep production and quality high while maintaining reasonable cost controls. One way of controlling costs is to use growing media that are locally available in good supply, and therefore of low cost. In Mississippi. as in other states in the southeast, pine bark is an available byproduct resource from the forestry industry; fines (<=95mm diameter) can be used as a growing medium following composting. Rice hulls are a readily available waste product from rice mills, especially in the Mississippi Delta region; these are suitable after being crushed and composted.

In comparison to plants grown in rock wool, yield from plants in pine bark fines, rice hulls, or sand were higher, while quality was not significantly different in the l-crop/year system. In a spring crop, yield and quality were higher from plants in pine bark, rice hulls, and rock wool than from those grown in sand. On a per plant basis, cost for the rock wool system, perlite system (pre-bagged), perlite (bulk), peat moss, sand, composted rice hulls, and pine bark lines are $1.50, $1.00, $0.35, $0.60, $0.24, $0.22 and $0.17, respectively. Pine bark and rice hulls are good choices for growing media for greenhouse tomatoes in areas where they are available.

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Richard G. Snyder

A successful greenhouse tomato crop depends on the optimization of several factors; among these factors are water, nutrition, and all facets of environmental control. Good pollination, however, is one of the most important requirements for the production of fruit of high yield and quality. Poor pollination causes fruit that are smaller, angular, or puffy, due to reduced seed numbers and poor gel fill in the locules. In Spring 1993, two 7.3 × 29.3 double plastic-covered greenhouses were used to compare the conventionally used electric pollinator to bumblebees for effective pollination; replicated variety trials were performed within each. In one greenhouse (12 replications, RCBD), `Trust' performed better than `Caruso' in yield and quality, although it was smaller in fruit size. In the other greenhouse (four replications, RCBD), `Match' and `Switch' were better than all others (`Belmondo', `Capello', `Laura', and `Rakata') for most yield and quality variables. Means across varieties were similar for the two pollination techniques, with marketable weights identical. For gutter-connected greenhouse ranges of 0.1 ha or larger, bumblebees are an economically viable option for pollinating hydroponically grown tomatoes.

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John C. Snyder, George Antonious, and Richard Thacker

Many accessions of Lycopersicon hirsutum are highly resistant to insects. Trichomes and their secretions have been extensively indicated as factors of resistance. One mechanism of resistance mediated by secretions is repellency, a mechanism that is consistent with the observation that few insects visit plants of L. hirsutum. Trichome secretions from certain accessions of L. hirsutum f. typicum are repellent to spider mites. However, the composition of secretions from different accessions of f. typicum are chemically diverse. Sesquiterpene hydrocarbons are prevalent in secretions, but are structurally diverse. How structure may relate to repellency is of interest but difficult to address because isolation of pure sesquiterpene hydrocarbons from hydrocarbon mixtures is difficult. To begin examining relationships between structure and activity we determined how chain length of n-alkanes related to repellency of spider mites. n-Alkanes having chain lengths from 8 to 22 carbon atoms were assayed for repellency. The C16-C18 alkanes were most repellent. Smaller and larger hydrocarbons were less repellent. The EC50 for n-hexadecane was equal to that of the most repellent natural products we have isolated from trichome secretions of L. hirsutum.

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Joseph H. Connell and Richard L. Snyder

Almond (Prunus dulcis Mill.) cultivars vary in tolerance to cold with flowers at pink bud more tolerant than at full bloom or than small nuts. Branch samples 60 cm long with 30-100 blossoms or nuts were cut, sprayed with water, and artifically frozen. Subsamples were removed after exposure to 4 to 6 successively lower temperatures for 30 minutes. After 48 hours of ambient temperatures, flowers or small nuts were sectioned and examined for visual evidence of injury. Of the early cultivars, `Peerless', is most sensitive at full bloom and `Sonora' is most hardy. `Sonora' is especially hardy at pink bud. `NePlus Ultra' is intermediate. Of the mid-blooming cultivars, `Carmel' is most sensitive to cold while `Nonpareil' is most tolerant. `Price' is intermediate. The late blooming cultivar, 'Mission' is most sensitive while 'Padre' and 'Butte' appear similar. This study compared several popular new cultivars to older industry standards.

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Richard G. Snyder, James E. Simon, Richard A. Reinert, Michael Simini, and Gerald E. Wilcox

Watermelon, Citrullus lanatus (Thunb.) Matsum & Nakai cv. Sugar Baby, were grown in the field as a fall crop in open-top chambers (OTC) in southwestern Indiana with either charcoal-filtered (CF) or nonfiltered (NF) air. Ozone and sulfur dioxide were continuously monitored in OTC and ambient air. There was a significant decrease in marketable yield by weight (19.9%, P = 0.05), percentage of marketable fruit by number (20.8%, P = 0.10), and total yield by weight (21.5%, P = 0.05) from plants grown in the NF air treatment compared with those grown in CF air. Ozone-induced foliar injury was significantly greater on plants grown under NF conditions. Ambient concentrations of 03 in southwestern Indiana caused foliar injury (P = 0.10) and significant yield loss to a fall crop of watermelons.

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Richard G. Snyder, Frank Killebrew, and Joseph A. Fox

Yellow squash (Cucurbita pepo L.) planted after early spring in Mississippi have a strong likelihood of developing green streaks and blotches on the fruit-symptoms of watermelon mosaic virus strain 2. Cultivars with the relatively new precocious yellow gene (PYG) tend to show such symptoms less prominently, and in some cases not at all, when infected. Field trials were conducted at two locations to evaluate several PYG cultivars and compare their WMV-2 symptoms to those of standard, non-PYG types. In both cases, the PYG cultivars had fewer unmarketable fruit due to WMV-2 symptoms, although they were not entirely immune to the virus.

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Thomas Horgan, Richard Snyder, Peter Hudson, Edgar Vinson, and Joseph Kemble

Ten “mini” or personal size seedless watermelons were evaluated at three locations: north and central Mississippi and in central Alabama. `Betsy', `Bobbie', `Demi-Sweet', `Extazy', `Mini Yellow', `Petite Treat', `Solitaire', `Valdoria', `Vanessa', and `Wonder' were the cultivars trialed. Seedlings were started, in a greenhouse, four weeks before planting. All locations used drip irrigation and black plastic mulch and were fertilized according to soil testing lab recommendations. A personal size diploid (seeded) variety, `Jenny', was used as the pollinator. One pollinator was planted, and interspaced evenly, for every three triploid plants. Four harvests were made at each location on 7-day intervals. Yields reported are based on 2,074 triploid plants per acre and 1,037 pollinizer plants per acre. Only the triploid yield reported. Plant spacing was 14 ft2 per plant. For total yield (lb/acre) the cultivars `Petite Treat' (27,210), `Valdoria' (25,700), and `Demi-Sweet' (26,400) were among the top producers at each location. `Mini Yellow' was a top producer at all locations averaging 22,480 lb/acre. For total yield (fruit/acre) the cultivars `Valdoria' (3,380), `Petite Treat' (3,470), `Bobbie' (3,470), `Betsy' (3,380), and `Vanessa' (2,740), were among the top producers at each location. For total yield (lb/fruit) `Betsy' (6.9), `Wonder' (6.7), and `Vanessa' (6.1) had the overall lowest individual fruit weights. `Demi-Sweet' had the highest individual fruit weight in central Alabama (10.0) and north Mississippi (8.8). One problem observed was that a number of melons among cultivars were above or below size class. Also determining melon ripeness was a challenge. Melon quality was good. The soluble solids concentration (sweetness) of all melons was excellent. `Demi-Sweet' had the highest incidence of hollowheart. `Wonder' and `Extazy' had no incidences of hollowheart at any location. Rind thickness had no significant differences, however in both locations measured `Mini Yellow' had the thinnest rind. Rind necrosis was not encountered.

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John C. Snyder, Richard Thacker, Jan St. Pvrek, and Jack P. Goodman

Spider mites (Tetranychus urticae Koch) readily colonize the cultivated tomato. Lycopersicon esculentum L. However, mites have extreme difficulty colonizing the wild relative of tomato, L. hirsutum Humb. and Bonpl. When mites approach leaves of L. hirsutum, they often veer away, suggesting the presence of a deterrent or repellent. Initial experiments indicated that trichome secretions on leaflets of L. hirstum deterred mites. In vitro bioassays indicated that at least four distinct compounds present in these sequiterpenoid secretions of L. hirsutum P.I. 251303 were deterrent. At least two of the compounds were soluble in dilute NaOH. Based on mass spectra and 1H and 13C NMR the structure of two base soluble compounds were established as two related bisabolane derived carboxylic acids.