Search Results

You are looking at 1 - 10 of 21 items for

  • Author or Editor: Frank Louws x
Clear All Modify Search

Organic heirloom tomato production is limited in the southeastern United States by foliar and soilborne diseases, thermal stress, and weathered soil structure. Heirloom cultivars command a premium market, but tolerance to disease and abiotic stress is often poor. Organic growers need research that supports the advantages of market niches afforded by heirloom tomatoes through the development of integrated systems to manage pests and reduce risks of associated crop losses or low yields. Two major soilborne diseases common in the southeast, bacterial wilt (caused by Ralstonia solanacearum) and fusarium wilt (caused by Fusarium oxysporum f.sp. lycopersici), were effectively managed using susceptible heirloom scions grafted onto resistant rootstock. In naturally infested soil, bacterial wilt incidence for nongrafted ‘German Johnson’ was 79% and 75% in 2005 and 2006, respectively. ‘German Johnson’ showed no symptoms of bacterial wilt in either year when grafted onto the resistant genotypes CRA 66 or Hawaii 7996. Fusarium wilt incidence was 46% and 50%, respectively, in nongrafted and self-grafted ‘German Johnson’ controls. When ‘Maxifort’ rootstock was grafted with ‘German Johnson’, no symptoms of fusarium wilt were seen, and plants with ‘Robusta’ rootstock had an intermediate level of disease (29%). An evaluation of commercially available rootstock was carried out in three separate experiments in diverse organic production systems to determine yield impacts with low disease pressure. ‘Maxifort’ rootstock significantly increased yield in one location (P = 0.05), but ‘Maxifort’ and ‘Robusta’ rootstock did not consistently impact yield at the other two locations. Grafting is an effective management tool for organic growers in the southeast United States to reduce risk of crop loss resulting from soilborne diseases and will be a valuable component in an integrated pest management program.

Free access
Authors: and

Grafting could potentially become an important part of integrated pest management programs in vegetable crops in the United States due to increased pathogen densities, reliance on pathogen susceptible varieties, increased use of organic and high tunnel production systems, limited land or input resources, value-added benefits, and the loss of, or regulatory restrictions on, soil fumigants. Adoption of this technology imposes additional costs on growers due to significantly higher grafted transplant prices, but associated yield improvements are potentially more than sufficient to offset the higher transplant costs. Therefore, the economic impact of the technology adoption depends highly on the specific circumstances of each grower. In this study, we propose a decision tool for growers to facilitate grafting technology adoption. We demonstrate an application of the proposed tool to a scenario based on real-life data for the open-field production of tomato (Solanum lycopersicum). The results show that based on a 30% loss in marketable yields due to disease pressure in nongrafted systems, yield improvements in the grafted system with resistant rootstock were sufficient to offset higher transplant and harvesting costs and resulted in higher net revenues. Net revenue estimates were $7126/acre in the nongrafted system and $8374/acre in the grafted system. The sensitivity analysis resulted in positive net revenues in the grafted system ranging from $108 to $12,328 per acre. Estimated marketable yield required in the grafted system to breakeven with the nongrafted system was 73,880 or 19,980 lb/acre more than marketable yield in the nongrafted system.

Free access

The growth and development of three strawberry cultivars commonly grown in a plasticulture system were documented. Strawberry plants were harvested monthly and divided by roots, crown, leaves, flowers, and fruit and then dried in an oven. The dry matter production and resource allocation proceeded along a predictable pattern of development. The establishment phase was characterized by an active period of growth of root, crown and leaves in the fall. Through the winter, the plants underwent slow growth, ending in a transition period in the late winter/early spring when resources were allocated to both vegetative and reproductive growth. In the spring, all plant parts received significantly increased allocation of, or redistribution of, resources. Cultivars of California origin, `Chandler' and `Camarosa', displayed similar trends in yield, dry matter production, seasonal resource allocation, and growth analysis variables throughout the season. `Sweet Charlie', a cultivar from Florida, showed lower dry matter accumulation and relative growth rate in the spring, higher harvest index and lower yield than the California cultivars.

Free access

We evaluated the influence of three compost sources and compost amended with T382 with fumigant Telone C-35 and various combinations of compost and Telone C-35 on the yield and pest management of cucumber, pepper, tomato, collard, southern pea, and summer squash in a multicrop rotational system. In the first year, there were few differences between the compost treatments and Telone C-35, but all treatments resulted in more yield than the control. In the second year, all compost treatments and/or Telone C-35 improved total and marketable yield of cucumber, pepper, tomato, southern pea, and summer squash. Furthermore, in the second year, Telone C-35 treat-ments produced more yield than some of the compost treatments in tomatoes. Combining Telone C-35 with compost did not differ from either treatment alone. Nematode and disease assessments were not consistent and will be discussed in further detail.

Free access

Strawberry (Fragaria × ananassa) `Chandler' plants from three sources were grown in the annual hill plasticulture system during two growing seasons (1996-97 and 1997-98). These trials evaluated the yield and vegetative performance of bareroot plants from Prince Edward Island and Ontario, Canada, and plug plant tips that were rooted in North Carolina but obtained from Ontario Canada. At the end of the season, total and marketable yields and fruit weight were not different among the plant sources. In addition, plants from all three plant sources produced equivalent yields on a weekly basis. Monthly whole plant harvests revealed that plant source did not affect leaf area, root, crown, leaf, flower or fruit dry weight during most of the growing season. In addition, plant growth parameters (specific leaf area, leaf area ratio, leaf weight ratio, and root to shoot ratio) in general did not differ among plant source in any 1 month. Plant growth did show shifts in dry weight allocation and leaf area as the season progressed that were uniform among plant sources, with the majority of the growth occurring in the spring in the two months prior to harvest. This uniformity among plant sources will allow future research to emphasize plant production practices that may reduce the risk of pest and disease problems or optimize production practices favored by growers.

Full access

At its most basic, grafting is the replacement of one root system with another containing more desirable traits. Grafting of tomato (Solanum lycopersicum) onto disease-resistant rootstocks is an increasingly popular alternative for managing economically damaging soilborne diseases. Although certain rootstocks have demonstrated ancillary benefits in the form of improved tolerance to edaphic abiotic stress, the mechanisms behind the enhanced stress tolerance are not well understood. Specific traits within root system morphology (RSM), in both field crops and vegetables, can improve growth in conditions under abiotic stress. A greenhouse study was conducted to compare the RSM of 17 commercially available tomato rootstocks and one commercial field cultivar (Florida-47). Plants were grown in containers filled with a mixture of clay-based soil conditioner and pool filter sand (2:1 v/v) and harvested at 2, 3, or 4 weeks after emergence. At harvest, roots were cleaned, scanned, and analyzed with an image analysis system. Data collected included total root length (TRL), average root diameter, specific root length (SRL), and relative diameter class. The main effect of cultivar was significant (P ≤ 0.05) for all response variables and the main effect of harvest date was only significant (P ≤ 0.01) for TRL. ‘RST-106’ rootstock had the longest TRL, whereas ‘Beaufort’ had the shortest. ‘BHN-1088’ had the thickest average root diameter, which was 32% thicker than the thinnest, observed in ‘Beaufort’. SRL in ‘Beaufort’ was 60% larger than ‘BHN-1088’. This study demonstrated that gross differences exist in RSM of tomato rootstocks and that, when grown in a solid porous medium, these differences can be determined using an image analysis system.

Full access

Interest and use of grafted tomato (Solanum lycopersicum) in the United States continues to grow. Pioneered in Asia, herbaceous grafting is a commonly used cultural practice to manage many soilborne pathogens. Bacterial wilt (BW), caused by the pathogen Ralstonia solanacearum, is an aggressive soilborne pathogen that affects tomato grown in the southeastern United States. Traditional fumigation methods have limited effectiveness in the management of this pathogen. The present study was conducted to compare the bacterial wilt resistance of three commercially available tomato rootstocks, which are purported to be resistant to bacterial wilt: ‘Cheong Gang’, ‘RST-04-106-T’, and ‘Shield’. The determinate hybrid tomato ‘Red Mountain’, which is susceptible to bacterial wilt, was used as the scion and nongrafted control. Three locations were used over 2 years in North Carolina: an on-farm site with a history of bacterial wilt and two North Carolina Department of Agriculture Research Stations with no recent history of bacterial wilt. No disease symptoms were observed in any of the three grafted treatments, whereas the nongrafted controls showed between 30% and 80% disease incidence at the on-farm location. The resultant rootstock-imparted resistance improved marketable yields by between 88% and 125% compared with the nongrafted plants. When grown in locations lacking BW there were no yield benefits to grafting with any of the three rootstocks.

Open Access

Organic and heirloom tomatoes are high-value products with growing demand but there are many challenges to successful cultivation. A systems comparison study was carried out to evaluate the production of the popular heirloom tomato ‘Cherokee Purple’ (Solanum lycopersicum L.) under high tunnel and open field systems in North Carolina from 2007 to 2008. Management of the high tunnel (i.e., temperature and irrigation), weather events as well as pest and disease pressure influenced crop quality and yield. The high tunnel and field systems achieved similar total yields (100 t·ha−1) the first season but yields were 33% greater in the high tunnel system than the field system in the second year (100 t·ha−1 and 67 t·ha−1, respectively). Both years, the tomatoes were planted in high tunnels 1 month earlier and harvested 3 weeks earlier than the field. The accumulation of ≈1100 growing degree-days (GDD) was required in both systems before 50% of the fruit was harvested. Fruit cracking, cat-facing, blossom-end rot, and insect damage were the major categories of defects in both systems. Incidence of both Tomato Spotted Wilt Virus (TSWV) and Gray Leaf Spot (GLS) were lower in the high tunnel compared with the field in 2007 and 2008, respectively. Results of this study suggest that with proper management techniques, high tunnels can optimize yields, increase fruit quality, and provide season extension opportunities for high-value horticultural crops.

Free access

In this study, we investigate the economic viability and environmental impact of three different soil management systems used for strawberry (Fragaria ×ananassa) production in the southeastern United States: 1) a conventional production system that is based on the current production practices implemented by growers, 2) a nonfumigated compost system with summer cover crop rotations and beneficial soil inoculants, and 3) an organic production system that includes practices approved for use under the National Organic Program (NOP). Under our assumptions, all three systems resulted in positive net returns estimated at $14,979, $11,100, and $19,394 per acre, respectively. The nonfumigated compost system and organic system also both resulted in considerable reductions in negative environmental and human health impacts measured by a set of selected indicators. For example, the total number of lethal doses (LD50) applied per acre from all chemicals used in each system and measuring acute human risk associated with each system declined from 118,000 doses/acre in the conventional system to 6649 doses/acre in the compost system and to 0 doses/acre in the organic system. Chronic human health risk, groundwater pollution risk, and fertilizer use declined as well in the compost and organic systems as compared with the conventional system.

Free access

Strawberry (Fragaria ×ananassa Duchnesne) growth and productivity were compared in fumigated and nonfumigated production systems. Strawberry transplants grown in potting mix amended with Trichoderma hamatum (Bonord.) Bainier, strain T382, Trichoderma harzianum Rifai, strain T22, or untreated, were planted in field plots treated with compost, compost amended with T. hamatum strain T382, Telone-C35, or not treated. Plants were sampled throughout the growing season, and dry weights of roots, crowns, leaves, flowers and fruit, leaf area, and total and marketable yield were determined. Trichoderma amendments to the potting mix improved plant dry weight and leaf area of strawberry transplants in the first year and suppressed root rot incidence in the second year but did not affect plant growth or disease incidence once the plants were set in the field. Field plants in fumigated plots had greater root, leaf, and crown dry weights, leaf area, and yield compared with plants in the other soil treatments. We conclude that Trichoderma amendments (1) alone had little benefit to plug plant growth and (2) in combination with compost, had no benefit to strawberry plant growth in the field. The task remains to develop a reliable and sustainable strawberry production system that does not rely on chemical fumigants.

Free access