Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Bacterial fruit blotch (Acidovorax avenae subsp. citrulli) continues to occur almost every year and has the potential to cause a disaster for the watermelon industry. Crimson Sweet watermelon (Citrullus lanatus var. lanatus) was crossed with two Citrullus lanatus var. citroides accessions shown to be resistant to A. avenae subsp. citrulli in previous work. Disease ratings of F1 and F2 populations from these two crosses suggested that the resistance is conferred by more than one gene and that the mode of inheritance may be complex. Resistant F2 plants from each of these two crosses were used in a backcrossing program with Crimson Sweet to obtain good horticultural characteristics in a resistant breeding line. Resistant plants with good horticultural characteristics were obtained in the third backcross progeny from each of the accessions. Bacterial fruit blotch resistant breeding lines with uniform resistance and good horticultural characteristics should be available after 3-4 more selfed generations of the BC3 progeny. PARTICIPANTS: There was collaboration on this project with A. Levi, USDA, ARS, U.Sl. Vegetable Laboratory, 2700 Savannah Highway, Charleston, SC 29414. Dr. Levi conducted research on finding genetic markers that could be associated with the resistance to bacterial fruit blotch in the accessions and breeding lines. TARGET AUDIENCES: The primary target audiences were watermelon seed companies and their breeders, as well as other research scientists around the world working on cucurbits. If the project is successful, the primary, final beneficiary will be watermelon seed producers, greenhouse growers, and watermelon farmers. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Exclusion of the causal bacterium from the field has been the only effective control of bacterial fruit blotch. The disease has the potential to cause a disaster in any area of the world that grows cucurbits. This disease has consistently been responsible for approximately $1 million in loss to the cucurbit industry per year in Florida and the Southeast. The findings that resistant watermelon plants could be developed in backcross progeny from the watermelon accessions means that resistance could become an important tool in the control of bacterial fruit blotch in cucurbits. The development of resistant cultivars of watermelon would greatly reduce, or eliminate, the threat from this disease to the industry.
Publications
- Hopkins, D. L. and Levi A. 2008. Progress in the development of Crimson Sweet-type watermelon breeding lines with resistance to Acidovorax avenae subsp. citrulli. Cucurbitaceae 2008: Proceedings of the IXth EUCARPIA Meeting on Genetics and Breeding of Cucurbitaceae, 2008:157-162.
- Wen, A., Mangravita-Novo, A., Hopkins, D.L., and Norman, D.J. 2008. Genetic characterization of Acidovorax avenae subsp. citrulli using amplified fragment length polymorphism (AFLP). Phytopathology 98:S169.
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Progress 10/01/06 to 09/30/07
Outputs
In Florida, inoculation of Cabernet Sauvignon with a benign strain (EB92-1) of X. fastidiosa subsp. piercei provided control of Pierce's disease for more than 10 seasons in the research center vineyard; whereas, all nontreated vines died within 4 years. Treated Chardonnay vines have remained free of PD in 2 commercial vineyards in central Florida for 3 years. In other commercial vineyards, EB92-1 appears to be controlling PD in the cultivars, Cabernet Sauvignon, Cabernet Franc, Chenin Blanc, Mourvedre, Seyval Blanc, and Vidal Blanc. In the research center vineyard, treated American cultivars Chambourcin and Cynthiana also are free of PD. To gain understanding of the mechanism of biological control by the benign strain, colonization and movement of the pathogenic strain in Carignane grapevine protected by the biocontrol strain was determined in greenhouse tests using the enhanced cyan fluorescent protein gene and the enhanced yellow fluorescent protein gene as markers
to distinguish the two strains in planta. The biocontrol strain colonized the grapevines at a level that was at least 100-fold lower than pathogen populations associated with disease development. The biocontrol strain reduced systemic colonization by the pathogen by 10 to 100 fold, compared to plants inoculated with pathogen only. Systemic movement of the pathogen in the plant was limited by the biocontrol strain. The biocontrol strain appears to prevent PD development by limiting the pathogen population below the threshold level for symptom production in grapevine.
Impacts
The success of this project will result in control strategies for Pierce's disease of grapevine that is environmentally friendly. This would give a tremendous boost to the grape industry in areas where Pierce's disease is a limiting factor, such as the southeastern US and parts of California. It could enable the establishment of a wine industry based on Vitis vinifera grapes.
Publications
- Reddy, J.D., Reddy, S.L., Hopkins, D.L., and Gabriel, D.W. 2007. TolC is required for pathogenicity of Xylella fastidiosa in Vitis vinifera grapevines. Mol. Plant-Microbe Interact. 20:403-410.
- Livingston, S., Chen, J., Chang, C., Hopkins, D., Hotchkiss, M., Reilly, C., and Civerolo, E. 2007. Genotypic and phenotypic characterization of Xylella fastidiosa strains isolated from California, Georgia, and Florida. Phytopathology 97:S67.
- Hopkins, D. 2007. Biological control of Pierces disease of grapevine with benign strains of Xylella fastidiosa subsp. piercei. In 2007 Pierces Disease Research Symposium Proceedings, California Dept. Food & Agric., pp. 202.
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Progress 10/01/05 to 09/30/06
Outputs
In the Mid-Florida REC vineyard and commercial vineyards tests are underway to evaluate benign strains of Xylella fastidiosa for the biocontrol of Pierce's disease in grape cultivars with different levels of tolerance to the disease. During 2005-2006, the second full season for Cabernet Franc, Chambourcin, and Cynthiana in the MREC vineyard, symptoms began to develop. X. fastidiosa strain EB92-1 was effective in reducing symptom development in all 3 cultivars. Incidence of mild symptoms was reduced from 66% to 17% in Cabernet Franc and no symptoms were observed in Chambourcin or Cynthiana treated with EB92-1. Other tests include the cultivars Barbera, Chardonnay, Chenin Blanc, Ruby Cabernet, and Golden Muscat.
Impacts
The success of these tests would have a tremendous effect on the grape industry in areas where Pierce's disease is a problem, such as the southeastern US and California. This would allow the production of Vitis vinifera in the Southeast.
Publications
- No publications reported this period
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Progress 10/01/04 to 09/30/05
Outputs
In the Mid-Florida REC vineyard as well as commercial vineyards, tests have been started to evaluate benign strains of Xylella fastidiosa for the biocontrol of Pierce's disease in grape cultivars with different levels of tolerance to the disease. A biocontrol strain of X. fastidiosa originally isolated from elderberry has been most effective in providing cross-protection against Pierce's disease in the greenhouse and one vineyard test. This strain is being evaluated in grape cultivars Cabernet Franc, Chambourcin, Cynthiana, Barbera, Chardonnay, Chenin Blanc, Ruby Cabernet, and Goldon Muscat. Natural infection pathogenic X. fastidiosa will occur through sharpshooter vector feeding on the vines. The vines were planted into the vineyards in 2004 and are being monitored for symptom development.
Impacts
The success of these tests would have a tremendous effect on the grape industry in areas where Pierce's disease is a problem, such as the southeastern US. This would allow the production of European type bunch grapes (Vitis vinifera) in the Southeast.
Publications
- Hopkins, D.L. 2005. Biological control of Pierce's disease in the vineyard with strains of Xylella fastidiosa benign to grapevine. Plant Disease 89:1348-1352.
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Progress 10/01/02 to 10/01/03
Outputs
In greenhouse tests, weakly virulent strains of Xylella fastidiosa provided cross protection against Pierce's disease in V. vinifera Carignane. Strains originally isolated from elderberry were often the most effective biocontrol strains against Pierce's disease of grapevine; however, weakly virulent strains from grapevine were also effective. Elecroporation was used to integrate fluorescent protein genes into the X. fastidiosa genome. Different strains of the bacterium were transformed with either green fluorescent protein gene or a yellow fluorescent protein gene. The genes were expressed in the xylem vessels of grapevine. This allows the visualization of both a biocontrol strain and the pathogen in the host tissue.
Impacts
This technique will allow studies of the interaction of biocontrol strains of X. fastidiosa and pathogenic strains in the host tissue, which will allow further development of biological control of Pierce's disease. Successful development of the biocontrol could allow the production of European type bunch grapes in the southeastern US.
Publications
- Hopkins, D. L., Wichman, R. L., and Thompson, C. M. 2003. Molecular and pathogenic characterization of various pathotypes of Xylella fastidiosa. Proc. of 8th Int. Congress of Plant Pathol. 2:284.
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Progress 10/01/01 to 10/01/02
Outputs
Thirty-seven strains of Xylella fastidiosa originally isolated from 12 different hosts were characterized by ability to colonize 13 host species, SDS-PAGE of proteins, ERIC-PCR, REP-PCR, and pulsed field electrophoresis of genomic DNA digested with rare-cutting restriction endonucleases. Four strains had apparently lost pathogenicity, since they did not colonize any host. Most strains were more virulent on their host of origin than on any other host, and many of the strains were host specific. Periwinkle was colonized by more different strains of X. fastidiosa than any other plant host. Based on the presence, absence, or difference in intensity of 9 protein bands within the 21.5 kDa to 45.0 kDa molecular mass range, the strains could be subdivided into four distinct pathogenic groups and a miscellaneous group that included straims from several different hosts of origin. Using REP-PCR, ERIC-PCR, and PFGE generated DNA fingerprints, strains were grouped into clusters
that corresponded very closely with host range results. This data supports the separation of X. fastidiosa strains into pathovars.
Impacts
Characterization of X. fastidiosa at the pathovar level and development of techniques to rapidly differentiate the pathovars are fundamental for further progress in studies on the epidemiology, and control of these diseases that result in large losses in many economically important agricultural plants, including grapevine, peach, plum, coffee, and citrus.
Publications
- Hopkins, D. L. and Purcell, A. H. 2002. Xylella fastidiosa: Cause of Pierce's disease of grapevine and other emergent diseases. Plant Dis. 86:1056-1066.
- Wichman, R. L. and Hopkins, D. L. 2002. Differentiation of pathogenic groups of Xylella fastidiosa strains with whole-cell protein profiles. Plant Dis. 86:875-879.
- Jayasankar, S., Li, Z., Hopkins, D. L. and Gray, D. J. 2002. Induction of systemic, broad spectrum disease resistance in grapevine by in vitro selection. (Abstr.) Proc. of the 10th IAPTC & CB 10:97.
- Wichman, R. L., Thompson, C. M. and Hopkins, D. L. 2002. Pathogenic and genetic relationships among strains of Xylella fastidiosa isolated from various hosts. (Abstr.) Phytopathology 92S:86.
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Progress 10/01/00 to 10/01/01
Outputs
In greenhouse tests, weakly virulent strains of X. fastidiosa provided cross protection against Pierce's disease in V. vinifera 'Carignane'. In a 4-year test in the MREC, Leesburg vineyard, one weakly virulent X. fastidiosa strain provided significant control of Pierce's disease of grapevine in Cabernet Sauvignon on Freedom rootstock. Five of six treated vines survived five years and fruited. All six of the untreated vines died. Other weakly virulent strains of X. fastidiosa provided some biocontrol of Pierce's disease but were less effective, with 2 or 3 surviving vines. In recently completed experiments conducted over a 5-year period in a citrus grove with severe citrus blight, it was shown that twice yearly injections with benign strains of X. fastidiosa can reduce citrus blight spread by 50%. In a currently-running experiment in the same grove, none of the trees receiving a single injection of a benign strain of X. fastidiosa have developed citrus blight over a
2.5 year period; whereas, 16% of the untreated trees have developed blight over the same time.
Impacts
Pierce's disease prevents the development of a grape industry in Florida and the Southeast based on the high-quality Vitis vinifera grapes. The development of a biological control for Pierce's disease could result in an expansion of the Florida grape industry to include some of the high-value V. vinifera cultivars. On citrus blight, this research could result in a practical biological control method for blight involving cross protection that would reduce individual grower=s losses and the $52 million annual loss to the citrus industry by 50%, or more.
Publications
- Chen, J. , R. L. Jarret, X. Qin, J. S. Hartung, C. J. Chang, and D. L. Hopkins. 2000. 16S rDNA sequence analysis of Xylella fastidiosa strains. System. Appl. Microbiol. 23:349-354.
- Hopkins, D. L. 2001. Pierce's Disease. In: The Encyclopedia of Plant Pathology. Editors: Maloy, O. C., Murray, T. D., John Wiley & Sons, Inc., pp 771-772.
- Hopkins, D. L. 2001. Xylem-Limited Bacteria (RLOs). In: The Encyclopedia of Plant Pathology. Editors: Maloy, O. C., Murray, T. D., John Wiley & Sons, Inc., pp 1212-1213.
- Hopkins, D. L. 2001. Xylella fastidiosa. In Laboratory Guide for Identification of Plant Pathogenic Bacteria, 3rd Edition, ed. Schaad, N. W., Jones, J. B., and Chun, W., APS Press, pp 201-213.
- Hopkins, Donald L., Wichman, Rebecca L. 2001. Pathogenic and Molecular Relationships among Strains of Xylella fastidiosa from Grapevine and American Elder. In: Proceedings of the 10th International Conference on Plant Pathogenic Bacteria, pp 161-164.
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Progress 10/01/99 to 09/30/00
Outputs
Whole-cell protein SDS-PAGE was evaluated as a method of differentiatingstrains of X. fastidiosa obtained from elderberry, grapevine, lupine, oak, oleander, and sycamore. Different protein banding patterns were observed between 21,500 and 45,000 daltons. Based on the presence or absence, or difference in intensity, of one or two protein bands within that molecular weight range, the strains had been separated into six groups: grapevine and lupine(1 strain); elderberry; oak; oleander; sycamore; and lupine(1 strain). This work has been expanded to include ATCC strains from mulberry, almond, plum, elm periwinkle,ragweed, red oak, and grapevine. SDS-PAGE of whole-cell proteins can be used to differentiate among several pathotypes of X. fastidiosa and could be used to compare a new strain with known pathotypes. Pulsed-field gel electrophoresis (PFGE) of DNA fragments generated with rare cutting restriction endonucleases was used to differentiate strains of X. fastidiosa
from blackberry, citrus, elderberry, grapevine, lupine, oak, oleander, and sycamore. Similarity coefficients of 50 strains from these various hosts were analyzed using the Phylogeny Inference Package (PHYLIP 3.5) and a phenogram was created. The strains separated out into two major groups, Pierce's disease causing strains and tree strains. There were 9 subgroups in the 2 groups.
Impacts
The discovery that whole-cell protein SDS-PAGE can be utilized to differentiate strains of Xylella fastidiosa will be important in identifying alternate hosts of specific pathotypes of X. fastidiosa that are important in the epidemiology and control of diseases such as Pierce's disease of grapevine. It would also allow the rapid identification of new pathotype of X. fastidiosa or a new host of an old pathotype.
Publications
- Wichman, R. L. and Hopkins, D. L.. 2000. Differentiation of pathotypes of Xylella fastidiosa by SDS-PAGE of proteins. (Abstr.) Phytopathology. 90:129.
- Hopkins, D. L. and Harris, J. W. 2000. A greenhouse method for screening grapevine seedlings for resistance to anthracnose. HortScience. 35:89 -91.
- Wichman, R. L., Hopkins, D. L. and Wichman, T. A. 2000. First report of oleander leaf scorch caused by Xylella fastidiosa in Florida. Plant Disease. 84:198.
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Progress 10/01/96 to 09/30/97
Outputs
Experiments were conducted to test the efficacy of commercial and experimental postharvest dip treatments for use in prolonging the vase life of leatherleaf fern (Rumohra adiantiformis) fronds. Two commercial products (Hydroseal and Pixie Sparkle) and several experimental ones were effective in prolonging the postharvest longevity of the harvested fronds during those times of the year when fern wilt is a problem.
Impacts
(N/A)
Publications
- STAMPS, R.H. 1997. Oil-based postharvest dip treatments and leatherleaf fern. Univ. of Fla., Inst. of Food and Agr. Sci., Coop. Ext. Serv., Cut Foliage Grower 12(2):1- 4.
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Progress 10/01/95 to 09/30/96
Outputs
A grower survey was conducted to determine the scope and rate of increase of leatherleaf fern (Rumohra adiantiformis) anthracnose in Florida. The disease is caused by Colletotrichum acutatum and has spread exponentially since its first detection in 1993. Control measure that had been tried were ascertained.
Impacts
(N/A)
Publications
- STAMPS, R., D. MCCOLLEY, D. NORMAN and J. STRANDBERG. 1995. Results of leatherleaf fern anthracnose survey. Univ. of Fla., Inst. of Food and Agr. Sci.,Fla. Coop. Ext. Serv. Cut Foliage Grower 10(9/10):1-4.
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Progress 10/01/94 to 09/30/95
Outputs
Research on new anthurium cultivars has been expanded to include additional cultivars and reduced fertilizer rates. This NxK factorial utilized rates of 600, 900, 1200 and 1800 lb N and K/A/yr. Best quality plants and highest flower number was obtained at 600 lb N and 600 or 900 lb K. Higher N rates were especially detrimental to flowering. Several experiments have been established to determine effects of 600, 900, 1800 or 2400 lb N and K/A/yr on growth of Hedera cultivars in baskets. Part of the project includes determination of cutting quality from the first cutback as well as rootability of cuttings. Preliminary results indicate best plant quality and rootability of cuttings in the range of 1200 lb N and K/A/yr.
Impacts
(N/A)
Publications
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Progress 10/01/93 to 09/30/94
Outputs
1) Algae control in circulating greenhouse cooling systems is a continuing problem. We have developed a replicated test bed to compare up to twenty different algae control materials. Best algae control was obtained with WTB-28 at 2 oz or WBC-325 and WTB-28 at 1 oz each per 100 gallons water. Good algae control was also obtained with Prevent and Greenshield . 2) Forty-six containers of Syngonium podophyllum were transplanted from 15-cm to 20-cm pots and placed on a subirrigation system which supplied nutrient solution through a wick extending from inside the pot to a constant level supply below the pot base. The plants were grown to salable size on the system within two months and then maintained, with minimal pruning and without a serious problem with the system, for approximately six months. The system will be redesigned using the same concept and built with more cost-effective components for further evaluation.
Impacts
(N/A)
Publications
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Progress 10/01/92 to 09/30/93
Outputs
Current research involves development of a constant level irrigation system for container- grown greenhouse plants utilizing a capillary wick to move nutrient solution from constant level channels below the potted plants to the plant root zone. Present research has involved growing plants in cell trays and 10 to 15 cm pots using the subirrigation technology described above. Preliminary results of this work indicate that crops of equal quality to those grown by commercial nurserymen can be produced with the new subirrigation system. The system described is a nonrecirculating, closed, subirrigation system which uses less water than any of the commercially manufactured subirrigation systems available to nurserymen.
Impacts
(N/A)
Publications
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Progress 10/01/91 to 09/30/92
Outputs
The most recent experiment with prepackaged potting medium units, Florida Pot Packs (FPP's) have shown that during production of Dieffenbachia maculata `Compacta' in 15-cm containers, it is possible to save 44% of the water, 63% of the fertilizer and 93% of the plastic normally required by plants produced in conventional molded plastic pots when plants are grown in the FPP's. Although dieffenbachia were used in this experiment, the FPP should function similarly with other containerized horticultural plants.
Impacts
(N/A)
Publications
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Progress 10/01/90 to 09/30/91
Outputs
Studies involving prepackaged potting medium units (Florida Poly-Pot-Packs) havedemonstrated that over 40% of the moisture utilized in the production of some greenhouse potted plants can be saved through use of the packs. It was further demonstrated that the present fertilizer recommendation for production of dieffenbachia can be reduced by 50% or more when using the packs and a savings of over 90% in container plastic is realized when plants are marketed in the pack, without a rigid plastic container. Fungicide treatments were evaluated for control of Tubakia dryina on Laurel oak. Propiconizole treatments significantly increased growth rate and reduced disease damage. New leaf growth from laurel oak trees severely infected with Tubakia dryina emerged with greatly reduced infection levels following injection of propiconizole through prop roots. Fungicide treatments to cuttings of Magnolia and Camellia spp. applied by soaking cuttings for up to 1 hour increased
survival and rooting percentages and root growth. Tropical Plant Industry Exhibition Survey: Trade shows are a major marketing tool of the ornamental industry, yet producers complain of stagnant or falling participation. We conducted a survey to identify buyer motivations for attending the show.
Impacts
(N/A)
Publications
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Progress 10/01/89 to 09/30/90
Outputs
Studies involving prepackaged potting media units (the Florida Poly-Pot-Pack) have demonstrated that approximately 30% of the moisture utilized in greenhouse pot plant production can be saved through the use of the pot packs. Continuing efforts will show significant savings in fertilizer utilization, generation of plastic waste and shipping costs.
Impacts
(N/A)
Publications
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Progress 10/01/88 to 09/30/89
Outputs
Preliminary research was conducted on the mode of action of fosetyl aluminum (Aliette 80WP) in bacterial disease control. Fosetyl aluminum has been found to reduce severity of many diseases of ornamentals caused by Xanthomonas campestris pathovars, but not Erwinia chrysanthemi or Pseudomonas cichorii. Since pH of fosetyl aluminum is about 3.5 to 4.0, the effect fo pH on bacterial growth was tested. Most pathovars of X. campestris, P. cichorii and E. chrysanthemi had a minimum pH requirement for growth at about 4.5 to 5.0. Direct toxicity of fosetyl aluminum occurred at 750 to 1000 ppm for X. campestris pathovars. A combination of direct and indirect modes of action have been suggested for fosetyl aluminum and pythiaceous fungi and are potentially active in bacterial control as well. Research continued on characterization of Rhizoctonia-like organisms from ornamental plants. Of 269 isolates, 113 were from roots, 61 were from stems, and 95 were leaves. Of 110
multinucleate isolates, 32 were R. solani and 5 were R. zeae from roots, 28 were R. solani from stems, and 46 were R. solani from leaves. The remaining 159 isolates were binucleate organisms. Of the 105 R. solani isolates, about 60% were AG4, 20% were AG1 and 20% could not be typed in the first four anastomosis groups of R. solani. R. solani isolates were generally pathogenic on their hosts of origin as were binucleate isolates from leaves. Binucleate isolates from roots were not demonstrated pathogenic in these tests.
Impacts
(N/A)
Publications
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Progress 10/01/87 to 10/30/88
Outputs
Research was initiated on the effects of nitrogen-potassium-phosphorus ratios onseverity of Xanthomonas leaf spot of schefflera and Xanthomonas blight of anthurium. Although all three elements decreased severity of disease on schefflera when they were increased, ratios were not important. Characterization of Rhizoctonia-like organisms from ornamentals indicated that strains were isolated from roots, stems and leaves at 33, 22, and 45% respectively. Strains from leaves were 52% multinucleate and 48% binucleate. Strains from stems were 42% multinucleate and 58% binucleate. Strains from roots were 24% multinucleate and 76% binucleate. The majority of multinucleate strains were Rhizoctonia solani AG4. Laboratory tests on characterization of strains of Xanthomonas campestris from ornamentals included utilization of gelatin, starch, aesculin and asparagine, and fatty acid analyses. Pathogenicity under greenhouse conditions was confirmed for at least one host species on
approximately 450 strains. Further work will be conducted to define an identification scheme for pathovars of X. campestris. Fosetyl aluminum was tested for control of bacterial diseases of ornamentals. In general the compound worked as well as the labeled standard for Xanthomonas diseases of greenhouse ornamentals but did not work against Erwinia blight of Philodendron selloum or Agrobacterium tumefaciens on tomato.
Impacts
(N/A)
Publications
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Progress 10/01/85 to 10/30/86
Outputs
1) Foliage growers must now compromise between the high cost of fuel and a temperature which still produces profitable crops. To determine if lowering thermostats infrequently is feasible an experiment was conducted by growing plants at one minimum night temperature during most of the week, but subjecting plants to lower temperatures 1, 2 or 3 nights a week. Results indicate that tropical foliage plants will grow faster at minimum night temperatures of 70F, but 65F will produce plants of almost equal quality with considerable saving in fuel costs. Additional savings can be realized if thermostats are lowered to 50F 1-2 nights a week when nights are abnormally cold. 2) An experiment was conducted to determine if Viterra 2 Hydrogel, a hydrophilic soil amendment, would benefit growth and wilt resistance of Brassaia actinophylla under interior environments. Results showed that Viterra 2 increased moisture in the potting medium, but did not improve plant growth or
increase days to wilt). 3) Nephrolepis exaltata 'Compacta', Cyrtomium falcatum, Davallia solida, and Rumohra adiantiformis were grown under 47%, 63% and 80% shade. Production of all 4 ferns was better under 80% shade. Data on vase life of cut fronds and carbon exchange and transpiration of intact fronds is being analyzed.
Impacts
(N/A)
Publications
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Progress 10/01/84 to 10/30/85
Outputs
1) Syngonium 'White Butterfly' is affected by a serious blight which turns leaves first water soaked then necrotic. Experiments were conducted to determine effects of temperature on growth and blight development of 'White Butterfly'. Gains in growth by increasing temperature from 15 to 21C were slight and do not warrant the added expense of the fuel. Minimum air temperatures between 15 and 21C and water temperatures between 15 and 21C produce salable plants. 2) Seven foliage plant genera, Aphelandra, Epipremnum, Maranta, Nephrolepis, Philodendron, Pilea, and Syngonium were grown to salable size in 10-cm pots. Plants were then placed under simulated shipping conditions of 10, 13, 16, or 19C for 7, 14, 21, or 28 days prior to placement in a low light interior environment. Plants were graded at time of removal from shipping containers and again 2 weeks later. Plant grade decreased as simulated shipping time increased for all genera, with 14 days being maximum for
quality retention of most plants. Highest grades for most genera were maintained when plants were shipped at 13 or 16C. 3) An experiment was initiated to determine the effects of production shade level on the postharvest and postproduction longevity of 4 commercially important fern species. Cyrtomium falcatum, Davallia solida, Nephrolepis exaltata and Rumohra adiantiformis are being grown under 47%, 63% and 80% shade. Carbon exchange and yield data will also be taken.
Impacts
(N/A)
Publications
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Progress 10/01/83 to 09/30/84
Outputs
Four Nephrolepis exaltata cultivars and Epipremnum aureum were grown on advancedsecondary efficient wastewater, a standard water source or deionized water. Plant responses to the water sources were similar, with all water sources providing high quality plants. Emerging fronds of Rumohra adiantiformis were tagged every 4 weeks for one year and harvested every 4 weeks starting 6 weeks after tagging. Fern fronds that reached maturity in the shortest time and were tallest had reduced vase life. This corresponded to fronds that emerged during June, July or August.
Impacts
(N/A)
Publications
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Progress 01/01/83 to 12/30/83
Outputs
Leaf shine compounds applied to Ficus benjamina just prior to simulated shipmentreduced their tolerance to low light stress as indicated by an increase in the light compensation point (LCP). Compared to the control treatment, LCP was increased by an average over two experiments of 26, 22, 16 and 19 percent for Voleck oil spray (1%), Green Glo Plant Shine, Foliage Plant Leaf Polish and Luster Leaf, respectively.
Impacts
(N/A)
Publications
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Progress 01/01/82 to 12/30/82
Outputs
Incidence of postharvest wilting and yellowing of leatherleaf fern was recorded biweekly for 3 years on fern collected at 3 commercial ferneries in central Florida. Wilt appeared as premature senescence of fronds 1-9 days following harvest rather than appearing after 9-28 days which is the normal longevity for cut fern. Wilt occurred every month except March and April with yellowing found year round. Greatest severity for both occurred during July, August, September, and October. Maximum leatherleaf fern wilt after 12 days postharvest in 1979-80 was 48%, in 1980-81 62%, and in 1981-82 40%.
Impacts
(N/A)
Publications
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Progress 01/01/81 to 12/30/81
Outputs
Three experiments with foliage plants have shown that dark storage periods up to9 days are not detrimental to Aphelandra squarrosa or Philodendron scandens oxycardium and only slightly decreased quality of Dieffenbachia maculata. Quality of Ficus benjamina were decreased at 9 or 12 days of dark sotrage when grown under 30% shade versus 60% shade or when they received 160 mg N/25.4 cm pot/wk versus 80. Light compensation points of Ficus benjamina sprayed with Orthene, MetaSystox R or Vydate were not different from control plants.
Impacts
(N/A)
Publications
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Progress 01/01/79 to 12/30/79
Outputs
No progress reports under this project this year.
Impacts
(N/A)
Publications
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Progress 01/01/78 to 12/30/78
Outputs
(1) Increasing fluoride concentration of the potting medium increased tiphorn onChamaedorea elegans, whether dolomite level was increased or not. Source of fluoride, from superphosphate or sodium fluoride at similar levels produced the same symptoms. (2) An experiment using Dracaena fragrans 'Massangeana' was established to determine whether high fertilizer levels or fluoride was responsible for leaf mottling. Preliminary data indicates that leaf mottling is more highly correlated with excessive fertilizer levels than excess fluoride. (3) Simulated mechanical harvesting of leatherleaf fern in alternate strips of 10, 15 and 20 cm wide every 2 or 3 months reduced yield as much as 50% when compared to a commercially harvested check. Best overall yield from simulated mechanically harvested plots was from 6-inch strips harvested alternately every 2 months.
Impacts
(N/A)
Publications
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Progress 01/01/77 to 12/30/77
Outputs
Ficus benjamina grown under 30 or 60% shade were stored in the dark for 0,3, 6, 9 or 12 days and subsequently placed under 1500 lux. Leafdrop and chlorophyll levels were determined after 30 days, and plants grown under 30% shade lost an average of 100 leaves while those under 60% shade only lost 40 to 50. Chlorophyll levels in mg/cmy decreased more rapidly in plants grown in 30% shade after dark storage. Cuttings of Wandering Jew were placed in fluoride solutions of 0.25, 0.50, 1.0, 2.0 or 5.0 ppm to determine whether leafspots were the result of phytotoxicity. Levels of 2 ppm or higher resulted in tipburn. Chlorosis of Christmas cactus was indicated to be due to a manganese deficiency or iron toxicity in 2 experiments completed during the year. Chlrosis of Schlumbergera 'White Christmas' was decreaed by increasing Mn in the absence of Fe, whereas chlorosis was made more severe by high levels of applied Fe.
Impacts
(N/A)
Publications
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Progress 01/01/76 to 12/30/76
Outputs
(1) Single eye leaf cuttings of Ficus elastica 'Decora' were taken from stock plants maintained under 0 or 30% shade and receiving 500 or 1500 lb N/A/yr. Best root number and grade was obtained at either light level from stock plants grown with the high fertilizer rate. (2) a simulated mechanical harvesting system is being used to harvest Leatherleaf fern (Polystichum adiantiforme). Treatments include hand harvesting and strip cutting of 4, 6 or 8 inch swaths every 2 or 3 months. Marketable yield has been reduced by 25 to 45% in mechanical harvested plots over hand harvesting. Poorest yields are being obtained from the 8 inch swaths cut every 2 months. (3) In addition to stock plant treatment discussed in (1) above, Ficus elastica 'Decora' single-eye leaf cuttings were either rolled and held with an elastic band, one-half removed and 0 or 5 lb Osmocote incorporated/ydDT of propagation mixture. Best rooting and shoot breaks occurred on cuttings from stock grown
under 30% shade on 1500 lb N/A/yr when leaves were cut and fertilizer was included in the potting mixture.
Impacts
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Progress 01/01/75 to 12/30/75
Outputs
Tipburn on Chlorophytum comosum was shown to be due to fluoride in the soil solution. Best plants were grown when potting media free of fluorine were used and soil pH was maintained near 6.0 to 5.5. Reduction of transpiration rate through lowered temperature and increased humidity were also helpful. Three micronutrient sources, Perk, Vigoro Supplement X and FTE-503 were incorporated into a potting medium composed of 2 peat-1 pine bark-1 shavings at 3 rates each.No differences in growth were observed for Philodendron, Brassaia or Aphelandra.However, FTE-503 was phytotoxic to Aphelandra at 1/4, 1/2 and 3/4 lb/cu yd of mix and to Brassaia at 1/2 and 3/4. Perk was phytotoxic to Brassaia at 1 1/2, 3or 4 1/2 lbs/yd(3). In all instances, phytotoxicity occurred as a chlorosis near leaf margins. Severe spotting of Dracaena fragrans 'Massangeana' has been determined to be due to fluoride phytotoxicity. Applications of superphosphate had been incorporated into the potting
medium more than 6 months before spottingoccurred. A factorial experiment with 4 levels of superphosphate 0, 5, 10 or 15lbs per yd incorporated into the potting medium along with 0, 5, 10 or 15 lbs dolomite has demonstrated that tipburn occurs readily on unrooted Stromanthe amabilis, at all rates of superphosphate, but rooted cuttings do not develop tipburn.
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Progress 01/01/74 to 12/30/74
Outputs
Uptake of 4 micronutrient sources at 3 levels each was determined on 3 foliage plant genera. Uptake data indicates wide variation across sources for the same element, and also wide variation between plant genera. This work will be of great benefit in designing micronutrient programs for specific plants were specific micronutrient deficiencies occur. Results from several experiments with fluoride toxicity of foliage plants has shown that plants in the following genera are injured when medium or water levels are higher than 1 ppm: Calathea, Chlorophytum, Cordyline, Dracaena, Maranta, Pleamele and Stromanthe. Results ofseveral experiments on foliage collapse of Dieffenbachia picta during propagation has shown that desiccation can be a major factor. During winter when forced hot-air heaters are being used, mist application should be continued24 hrs per day.
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Progress 01/01/73 to 12/30/73
Outputs
Influence of dilute solutions of HCl on removal of Ca and Mg oxide residues on several foliage plants was determined. Solutions of 0.1 N or less were not phytotoxic while 1 N or above was phytotoxic. HCl was not as effective in removing residues as would be required under commercial conditions. Test plantings under 3 shade types and at 2 nutritional levels have been made on Asparagus meyeri, A. falcatus and A. myriocladus. These are being screened for potential as cut foliage crops. Three types of polypropylene shade; 73% regular, 73% lath and a double layer of 47% regular with 1 layer removed in winter are being tested on establishment of leatherleaf fern planted with 8 types of rhizomes and or number of fronds. Preliminary data indicates size of rhizome is not as important as number of viable fronds at planting time. Two factorial experiments initiated on Dracaena deremensis 'Janet Craig' and Dracaena fragans 'Massangeana' to determine whether tip and marginal
necrosis were influenced by fluoride. Treatments included combinations of 0.5 or 10 lbs Dolomite or CaCO(3)/ydDT and 0, 5 or 10 lbs superphosphate. D. 'Massangeana' wasnot influenced by fluoride in superphosphate but D. 'Janet Craig' was severely injured.
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Progress 01/01/72 to 12/30/72
Outputs
Two experiments were established to determine the influence of potting soil incorporation of micronutrient sources and levels on growth of Maranta and Aphelandra. Grade of Maranta was decreased by addition of 1/3 or 3 lbs FTE 503/ydDT whereas 1/4 lb FTE 503, 1 1/2, 3 or 6 lbs. Perk and 1, 3 or 6 lbs Vigaro-X/ydDT were similar to the check. With Aphelandra, plant grade was decreased with FTE 503 only when dolomite was not incorporated, whereas flowering was severely decreased. Best overall potted Aphelandra was produced with a micronutrient supplement of 1 1/2 lb/ydDT. (2) Five levels of HCL (0, .001, .01, .01 and 1 Normal) were applied to six species of tropical foliage plants in an effort to remove residues of Ca and Mg. A level of 1 N was injurious, whereas 0.1 N removed approximately 50% of the undesirable residue; further trials are planned. (3) Tip cuttings of Cordyline terminalis 'Baby Doll' were placed in deionized water immediately after removal from stock
plantsand then at various time intervals moved to a solution containing 1 ppm F. Cuttings moved to F solution after 4 days in deionized water produced very little necrosis but cuttings in deionized water less than 4 days showed considerable necrosis after placement in F containing solutions.
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Progress 01/01/71 to 12/30/71
Outputs
(1) A test of stock sources of P. oxycardium has indicated the superiority of propagative material grown at the ARC-A. Growth of ARC-A cuttings was 35% greater than 2 sources and 80% better than 2 others after 9 wks, indicating benefits of improved stock production techniques developed at the center. (2) Several experiments have been concluded on Cordyline terminals 'Baby Doll' whichdemonstrated that fluoride toxicity was the cause of foliar necrosis occurring during propagation. Levels of 0.25 ppm F or above in irrigation water cause sufficient necrosis to make rooted cuttings unsalable. Subsequent tests have shown necrosis severity can be reduced by using calcined clay (Turface) for propagation or Ca(OH)(2) in the propagative medium. Additional methods of obtaining necrosis-free cuttings are under development. (3) Tests are being continued with manufactured propagative blocks: BR-8, Kys-Kube and Oasis, as they would be adapted to mechanized production systems.
(4) Methods of propagating Dieffenbachia exotica cuttings are being examined to obtain decreased leaf yellowing and loss. Factorial combinations of length of drying time and use of mist or no mist have been established. (5) Repeated weekly spray applications of 17 miticides to five mite-susceptible foliage plant species revealed marked differences in phytotoxicity. Miticides found safe at the recommended concentration were Acarol, Benlate, Carzol, Kelthane EC, Orthene, Pentac and Tedion; unsafe were Acaraben, Cygon, Delnav, Fundal, Fundal-Carzol, Kelthane WP, Meta Systox R, Morestan, Omite, Plictran and Volck Oil.
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Progress 01/01/70 to 12/30/70
Outputs
(1) Tests have been conducted with propagating blocks: BR-8, Kys-Kube and Oasis. Preliminary results indicate Kys-Kube perform the best. (2) Of 20 mediaused German Peat (GP)-Shavings (Shav)(1/1), Oxford Peat (OP)-Shav, Louisiana Peat (LP) and Bark produced the largest P. oxycardium. Bark-Clay-Sand, Bark-Vermiculite(Verm)-Sand, OP-Sand the smallest. GP-Bark, LP-Bark produced the largest Schefflera. GP-Sand, LP-Sand-Perlite (Perl), OP-Sand the smallest. (3) Of 18 media tested Zellwood Peat, OP,LP and GP all grew satisfactory plants.Additions of Perl and verm did not improve plant growth and in some cases Bark and Rice Hulls reduced growth. There was some indication of particular species preferring a specific media or medium. A pronounced case was D. 'Baby Doll' preferring calcined clay or LP. (4) Xanthomonas dieffenbachiae, an important foliar pathogen of P. oxy. was not controlled when recommended weekly sprays of streptomycin (200 ppm) were employed. Isolation
from diseased tissue from streptomycin sprayed areas onto streptomycin containing media revealed resistance and pathogen growth up to 1000 ppm streptomycin (the maximum concentration employed). Isolates from infected tissue derived from infested but non-sprayed areas did not exhibit tolerance to the antiobiotic. Bacteriocide evaluations for pathogen control, under field conditions, also initiated. (5) 10 herbicides were applied to foliage and landscape plants. Herbicides were applied every 3 months and data taken periodically depending upon crop growth. After harvesting, cuttings were stuck and rooting response noted. Rooting was not affected. (6) 15 industrial sterilants were applied to the fence row. Effectiveness of these compounds was noted every three months.
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Progress 01/01/69 to 12/30/69
Outputs
(1) Rooting Response of Four Ornamental Species Propagated in Various Media. The objective of this investigation was to determine rooting responses and growth of Philodendron oxycardium, Scindapsus aureus, Rhododendron indicum and Gardenia jasminoides cuttings rooted in German peat, calcined clay, BR-8 blocks and composted municipal refuse, and to determine their growth after potting. Cuttings rooted in peat and calcined clay generally were larger with better rootsystems than cuttings placed in the other two media and grew at a faster rate after potting. (2) Some observations on Imports and Exports of Floricultural Products with Special Reference to Latin America. During the past five years there has been a rapid growth in the commercial floricultural industry in various areas of the world. A large share of the expansion has taken place in Central and South America. Major countries exporting to the United States and other foreign markets include Brazil, Costa
Rica, Colombia, Ecuador, Guatemala, Honduras and Panama. (3) The Ornamental Horticulture Industry of Florida and its Implication to Production in Tropical Americas. This report presents economic and production facts on all facets of Ornamental Horticulture in Florida which will provide information for people interested in producing an ornamental crop in Tropical American countries. Current estimates showed that Florida producers marketed approximately $112 million of ornamental crops from 43,000 acres of land in 1968.
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