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Catherine S.M. Ku, John C. Bouwkamp, and Frank R. Gouin

Treatment combinations of four cultivars, 26 mixes, and three fertigation treatments were evaluated in a completely randomized design. Poinsettia cultivars included `V-14 Glory', `Red Sails', `Lilo Pink', and `Annette Hegg'. The 26 mixes were 25%, 33%, and 50% of eight compost sources blended with 1 peat: 1 perlite (v/v), and Sunshine mix and Pro-Gro were the control. The eight compost sources were yard waste, lime and polymer dewatered biosolid, municipal solid waste (MSW), co-composted MSW 1 and 2, crab waste, and poultry litter. Fertigation treatment was began on first, second, or third week after potting. Fertigation solution was 250 mg/L N from 21N–2.2P–15.8K. The controls produced premium quality plants with 38 cm in canopy diameter, 11 total number of branches, and 28 cm in shoot height. Poultry litter, yard waste, polymer dewatered biosolid, crab waste, and MSW produced good quality plants with canopy diameter ranging from 30 to 35 cm. The canopy diameter with 25% compost treatments were 6% to 20% greater than those with 50% compost treatments. Total number of branches, shoot height, canopy diameter, and plant grade with first week fertigation were only 3% greater than those with fertigation delayed 1 or 2 weeks.

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Christopher Worden, John C. Bouwkamp, Francis R. Gouin, and Charles McClurg

Vegetable culture with Municipal Solid Waste Compost (MSWC) amended soils was evaluated with the emphasis on crop and soil responses. There were three treatments of 0, 20, and 40 t·ha–1 of MSWC applied in the fall of 1993 to a Matapeake Silt Loam on the Eastern Shore of Maryland. The following spring the soil was prepared for planting tomatoes and green beans. All crop management practices were in accordance with the standard procedures followed in Maryland for each crop, except for the addition of the MSWC. Both crop yields were significantly increased with the addition of the MSWC. Following the bean crop, broccoli transplants were established in the fall of 1994. Again, the yields obtained with the MSWC plots as compared to the control were significantly greater. Soil properties were also favorably affected by the addition of the compost. Analysis of soil samples indicated significant increases with MSWC, such as cation exchange capacity, soil pH, percent organic matter, and water-holding capacity.

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Catherine S.M. Ku, John C. Bouwkamp, and Frank R. Gouin

Municipal solid waste (MSW) may be a potential substitute for peat substrate in soilless medium. Adequate N and P are needed for a complete composting of MSW. MSW piles treated with diammonium phosphate (MSWP) or without P on Mar. 1994 were cured for 5 months. In Fall 1994, a factorial treatment combination of nine mixes and 3 fertigation treatments were evaluated in a completely randomized design on soft-pinched, single-stem `Red Sail' poinsettia. Mixes were MSW or MSWP ranging from 33% to 100% by volume in 1 peat: 1 perlite (v/v) and Sunshine mix was used as the control. Fertigation treatment began on the 1st, 2nd, or 3rd week after potting. Fertigation solution contained 266 mg·liter–1 N from 30N–4.4P–8.8K. The total fertigations ranged from eight to 10 for the 13-week study. With MSW mixes, shoot dry mass at the week 1 fertigation was 36% larger than at the week 3 fertigation. At the week 3 fertigation, shoot dry mass with 100% MSWP was ≈53% greater than with the 100% MSW. Shoot dry mass with 100% MSWP was similar to the control at the week 1 fertigation.

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Kimberly H. Brown, John C. Bouwkamp, and Francis R. Gouin

Optimum conditions for composting encourage and maintain the growth of microorganisms. Aerobic conditions must be maintained along with a 30 C: 1 N ratio and appropriate moisture levels. Our research found that P along with C and N are primary nutrients required by the microorganisms involved in composting. Phosphorus is a very important component of ATP and ADP, which drive most biochemical processes and are therefore necessary to all energy-driven processes. Results of this experiment show that MSW treatments with a minimum of 120 C: 1 P result in significantly higher temperatures during the composting process; lower final C: N ratios; greater volume reduction; and more available N in the final product. Emphasis of ongoing research is to determine appropriate C: P levels.

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Catherine S.M. Ku, John C. Bouwkamp, and Frank R. Gouin

Maryland Chesapeake Bay crab industry generates ≈20 tons of crab waste annually. The crab waste compost (CWC) was a mixture of crab chum and saw dust that had an initial EC of ≈26 dS·m–1. In Fall 1994, soft-pinched single stem `Annette Hegg Red' poinsettias (Euphorbia pulcherrima) in 15-cm azalea pots were grown in media containing Sunshine mix, 1 CWC: S base mix (BM), 1 CWC: 2 BM,. 1 CWC: 1 BM, or 2 CWC: 1 BM. Base mix is a 1 peat: 1 perlite (v/v). Fertigation treatment with 266 mg·liter–1 N from 30N–4.4P–8.8K was began on the 1st, 2nd, or 3rd week after potting. The total fertigations ranged from 8 to 10 for the 13-week study. With Sunshine mix, shoot height and canopy diameter were ≈15% greater than with 16% CWC mix and were ≈27% greater than with 67% CWC mix. There was a ≈10% decreased in the shoot height and canopy diameter with increasing %CWC in mix from 17% to 67%, but there was no difference in number of branches among the CWC mixes.

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J.L. Maas, C. Gouin-Behe, J.S Hartung, and S.C. Hokanson

Bacterial angular leafspot disease (BALD) of strawberry, caused by Xanthomonas fragariae Kennedy & King, has dramatically affected commercial fruit and plant production throughout the world. Leaf lesions may kill leaves, while lesions on sepals make fruit unmarketable. The bacterium can kill stolon-tip plantlets that are being rooted for transplanting. Since plants become systemically infected, there is no adequate chemical control for BALD under conditions that favor development and spread of the disease. Strawberry is the only host and no cultivars or advanced selections have proven resistant to this disease. We screened 23 Fragaria ×ananassa, 13 F. chiloensis, 56 F. virginiana, and 2 F. vesca genotypes for resistance to two pathogenic isolates of X. fragariae (ATCC-33239, the original strain from Minnesota and Xf-3 from North Carolina). Leaves were inoculated by forcing bacterial suspensions into leaves under pressure with a syringe barrel and plunger. Plants were incubated in a moisture chamber for 3 days, followed by 1 week under mist and then placed on a greenhouse bench. Experiments were done twice for obviously susceptible reactions and three and four times for questionable and resistant reactions, respectively. Only two genotypes were found to show a resistant reaction: 80-4-38 (`Earliglow' (F. virginiana clone SG-26 from Georgia) and F. virginiana clone SG-89 (=Luby MS 7-7 from Minnesota). Each of these genotypes exhibited typical hypersensitive responses by walling-off inoculation areas. All other genotypes exhibited typical BALD symptoms 5 weeks after inoculation with both isolates.

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K.S. Lewers, J.L. Maas, S.C. Hokanson, C. Gouin, and J.S. Hartung

Bacterial angular leafspot disease (Xanthomonas fragariae Kennedy and King) of strawberry (Fragaria species and F. ×ananassa Duch. cultivars) has become increasingly important to strawberry fruit and plant production. Strawberry cultivars and species vary in susceptibility to infection. However, little is known regarding epidemiology of the disease and resistance to infection. Two octoploid genotypes, a native F. virginiana (US 4808, tested as SG-89) and a F. virginiana (SG 26) × F. ×ananassa (`Earliglow') hybrid (US 4809, tested as 80-4-38), previously were found to be highly resistant to two differentially pathogenic strains of X. fragariae representing two of four genotypic strain groups. Our objective was to determine the number of genes involved with resistance for these two strawberry genotypes, whether strawberry resistance is conferred by dominant or recessive alleles, and whether or not the heritability is high enough for breeders to reliably make selections of resistant individuals in breeding populations. About 120 F1 seedlings from crosses of susceptible `Sweet Charlie' with each of the two resistant genotypes were clonally propagated and challenged with each of four X. fragariae strains. These strains were selected to represent four genotypes of X. fragariae defined by repetitive element based PCR: ATCC 33239, Xf-3, Xf-6, and Xf-1425. Plants were quantitatively rated on a scale of 0 (resistant) to 5 (susceptible) in replicated evaluations. High estimates for broad sense heritability support the conversion of the quantitative disease scores to qualitative scores and the classification of genotypes as resistant or susceptible. The qualitative ratings were used to estimate the number of genes involved with resistance. Some segregation ratios fit a 7S:1R ratio, and others fit a 15S:1R ratio, indicating that three or four unlinked loci could explain the inheritance of resistance in these populations. The high estimates for broad sense heritability show that resistant progeny can be selected with confidence, though large populations will be needed to identify enough resistant progeny from which to select for other important traits.

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John L. Maas, John S. Hartung, Cristina Gouin-Behe, and Stan C. Hokanson

Bacterial angular leafspot disease (BALD) of strawberry (Fragaria sp. and F. ×ananassa Duchesne cultivars) has become increasingly destructive to strawberry fruit and plant production in Canada and the United States, as well as in other countries. The disease, caused by Xanthomonas fragariae Kennedy and King, was first documented in Minnesota in 1960, and has become of worldwide concern because of the economic impact of BALD in strawberry fruit and nursery-plant production and the lack of adequate disease control strategies. We tested 81 Fragaria genotypes, including representatives of F. ×ananassa, F. chiloensis (L.) Duchesne, F. virginiana Duchesne, and F. vesca L., for resistance to two pathogenic strains of X. fragariae. Two genotypes, a native F. virginiana from Minnesota and an F. virginiana × F. ×ananassa hybrid, were found to resist infection by both bacterial strains and may be potential sources of resistance to other strains of X. fragariae.