A survey was conducted in the 2001 growing season to determine the leafhopper species composition, abundance, richness, diversity, and evenness among trees of three elm (Ulmus sp.) cultivars, two U.S. National Arboretum (USNA) seedling selections of U. szechuanica Fang, and two USNA seedling selections of U. bergmanniana Schneid. in a mixed stand. Yellow sticky traps were used to qualify and quantify the number of aerial leafhoppers from 1 May 2001 until 4 September 2001. A total of 4,523 individuals, belonging to 39 species within seven leafhopper subfamilies, were trapped. The weekly mean number of leafhoppers collected was significantly higher on traps from `Patriot', followed by `Frontier' and `Prospector', than on traps from the USNA seedling selections. Although the weekly mean species richness for `Prospector' was lower than the other two cultivars, the three cultivars had higher mean species richness than the USNA seedling selections of U. szechuanica and U. bergmanniana. Diversity among cultivars was higher than among the USNA seedling selections. Ulmus bergmanniana 68983 and U. szechuanica 68986 shared the highest percentage of species similarity, while `Frontier' and U. szechuanica 68991 were the most dissimilar. Of the species collected, Agallia quadripunctata, Empoasca fabae and Graphocephala versuta were the most abundant. The other species were mostly rare based on their low abundance. Scaphoideus luteolus, the only confirmed vector of elm yellows in North America, was found among the elm cultivars only. Yet, the Cicadellinae leafhoppers that are vectors of Xylella fastidiosa, the causal agent of bacterial leaf scorch, were found among both the cultivars and USNA seedling selections. Such data could allow for the screening and selection of elms resistant to economically important leafhoppers.
Jo-Ann Bentz and Alden M. Townsend
Mathieu Ngouajio and Milton E. McGiffen Jr.
Organic agriculture is growing in importance worldwide. In the United States, the rate of increase of organic growers was estimated at 12% in 2000. However, many producers are reluctant to undertake the organic transition because of uncertainty of how organic production will affect weed population dynamics and management. The organic transition has a profound impact on the agroecosystem. Changes in soil physical and chemical properties during the transition often impact indirectly insect, disease, and weed dynamics. Greater weed species richness is usually found in organic farms but total weed density and biomass are often smaller under the organic system compared with the conventional system. The improved weed suppression of organic agriculture is probably the result of combined effects of several factors including weed seed predation by soil microorganisms, seedling predation by phytophagus insects, and the physical and allelopathic effects of cover crops.
Emily C. Baisden, Douglas W. Tallamy, Desiree L. Narango, and Eileen Boyle
for herbivores to locate and populate. Table 1. Treatments, plant species, and cultivars compared with straight species in terms of insect herbivory (abundance, species richness, and cumulative seasonal damage) in a common garden as well as with
Ian G. Lane, James Wolfin, Eric Watkins, and Marla Spivak
abundance and species richness in farm borders ( Blaauw and Isaacs, 2014 ; Morandin and Kremen, 2013 ), roadside verges ( Noordijk et al., 2009 , Hopwood et al., 2010 ), green roofs ( Braaker et al., 2014 ), and neighborhood gardens ( Pawelek et al., 2009
Ouina C. Rutledge and Patricia S. Holloway
The germination, establishment, survival, and public preference of four wild-flower seed mixes were evaluated in relation to irrigation and seasonal sowing date. The mixes included two commercial nonindigenous wildflower mixes, a commercial mix with indigenous and nonindigenous wildflowers, and an experimental mix composed exclusively of Alaska native wildflowers. The two latter mixes were sown with and without `Tundra' glaucous bluegrass (Poa glauca). The two nonindigenous mixes exhibited the greatest seedling establishment during the first season. Fall sowing and irrigation during seed germination significantly increased species establishment for all mixes. In the second season, 11 nonindigenous species did not reappear, whereas all of the indigenous species reappeared. The experimental mix had the greatest species richness of the six mixes in the second season. The addition of grass to the mixes did not significantly affect wildflower species richness in either the first or second season. Survey respondents preferred the nonindigenous wildflower mixes to those containing Alaska native wildflowers because of a greater mix of colors that appeared earlier in the first season than the other mixes. Alaska native species recommended for wildflower mixes include Polemonium acutiflorum, Lupinus arcticus, Hedysarum mackenzii, Arnica alpina, and Aster sibiricus.
The success of long-term vegetable production and maintenance of environmental quality is dependent on soil quality. Indicators of soil quality include cation exchange capacity (CEC), organic matter (OM), carbon (C), pH, and the number and community structure of soil organisms. The use of appropriate compost has been shown to improve soil quality and enhance the response to fertilizer, therefore improving growth and yield of vegetable crops. The objective of this study was to evaluate changes in the chemical and biological properties of soil in response to compost use in conventional vegetables production systems. A survey was conducted on 5 farms (three in Immokalee, and one each in Delray Beach, and Clewiston) growing tomato, pepper, and specialty vegetables. Most of the farms were applying composted yard trimming waste alone or in combination with biosolids or horse manure at application rates of between 7 to 112 Mg·ha-1 once a year. Soil samples were taken from composted and non-composted areas in each farm during Feb. and Mar. 2002. Soil pH, OM, C, K, Ca, Mg, Cu, Fe, MN and Zn were higher in the composted areas compared with the non-composted areas for each farm. CEC values in composted areas were double those in non-composted areas. Most importantly, application of compost enhanced the overall soil microbial activity as determined by total microorganism number, SRD (species richness diversity), and TSRD (total species richness diversity) of six functional groups including heterotrophic aerobic bacteria, anaerobic bacteria, fungi, actinomycetes, pseudomonads, and nitrogen-fixing bacteria, in all the participating farms. The greatest soil quality improvement was seen in soils receiving the highest rates of compost for the longest time.
Lynn Marie Sosnoskie*, John Cardina, Catherine Papp Herms, and Matthew Kleinhenz
Community composition of the soil seedbank were characterized 35 years after the implementation of a long-term study involving cropping sequences (continuous corn, corn-soybean, corn-oat-hay) and tillage systems (conventional-, minimum- and no-tillage). Germinable seeds within the top 10 cm of soil in early spring were identified and enumerated in 1997, 1998 and 1999. Species diversity, which was characterized by richness (S), evenness (E) and the Shannon-Weiner index (H'), was significantly influenced by crop rotation rather than tillage. Generally, diversity measures were greatest in the corn-oat-hay sequences as compared to the corn-soybean rotations and the corn monoculture. Species richness and H' typically declined with increasing soil disturbance (no-tillage > minimum-tillage > conventional-tillage), whereas E increased with more intense tillage. A synthetic importance value (RI), incorporating both density and frequency measures, was generated for each species in each plot. Multiresponse permutation procedures (MRPP) were used to examine differences in weed community composition with respect to management system for all three years. Results suggest that the weed seed community in a corn-oat-hay rotational system differs substantially, in structure and composition, from communities associated with continuous corn and corn-soybean systems. No tillage systems were significantly different in composition as compared to conventional tillage and minimum tillage treatments. Crop sequence and tillage system are important cultural methods of shifting weed species number and diversity, and therefore, community structure. Manipulation of these factors could help to reduce the negative impact of weeds on crop production.
Rhoda Burrows and Francis Pfleger
Growing a plant host in association with other plant species (i.e., increasing diversity) changes the composition of the associated arbuscular–mycorrhizal (AM) fungal community. We tested whether this alteration in the fungal community causes significant differences in the growth of Schizachyrium scoparium L. (Little Bluestem, a C4 grass) or Lespedeza capitata L. (Bush clover, a legume). Seedlings were transplanted into pasteurized soil inoculated with soil from monoculture plots of Schizachyrium or Lespedeza, respectively, vs. plots containing one, seven, or 15 additional plant species. Soil washes from a composite of the plots were added to all pots, including non-inoculated controls, to reduce differences in the non-AM microbial communities. Spore counts of the inoculum from Lespedeza plots showed increasing numbers of AM fungal spores and species richness with increasing plant diversity; this was not true with the Schizachyrium plots, possibly because Schizachyrium may be a better host to more species of AM fungi than Lespedeza. Both Schizachyrium and Lespedeza responded to inoculation with increased growth compared to non-inoculated controls. Tissue analyses of both species showed that inoculation increased the percentage of Cu, and lowered the percentage of Mn compared to control plants. Schizachyrium showed no significant differences in growth due to inoculum source (1-, 2-, 8-, or 16-species plots); while Lespedeza showed increases in root and shoot weights with increasing source-plot diversity.
Mark T.F. Highland*, Daniel C. Sclar, Elaine R. Ingham, Karen L. Gartley, and James E. Swasey
Compost has great potential for use in horticulture; however, the relationship between compost feedstock materials and resultant compost characteristics must be well understood. Research examining plant growth response from the addition of compost to container growing media is limited. This research had two parts: the first part examined the relationship between compost feedstock materials and resultant mature compost characteristics. The second part investigated plant growth responses when compost replaced the peat component of container growing media. Two feedstock treatments were aerobically composted in turned windrows. Compost characteristics examined include pH, EC, C:N Ratio, Solvita Maturity, and several biological characteristics (total and active bacteria, total and active fungi, protozoa, spore forming bacteria, E. coli O157:H7, and total coliformic bacteria). To examine plant growth response, compost was substituted for peat (from 0%-40% by total volume) in container growing media. Crops tested were Antirrhinum majus `Rocket White', Viola × wittrockiana `Crown Azure', Oriental Hybrid Lilium `Siberia', and Chrysanthemum × grandiflorum `Yellow Kodiak'. Quantitative plant growth response measurements (shoot fresh and dry weight, percent root necrosis, flower number, and flower size) were recorded and compared by treatment. Despite initial feedstock differences between the two compost treatments, both resulted in similar compost biology and species richness. Coliformic bacteria and E. coli O157:H7 levels were below detection limits in final compost. Choice of compost feedstock materials had a significant effect on the chemical characteristics of the finished product. Compost replacement for peat resulted in plant growth greater than or equal to those of the control treatment.
George E. Fitzpatrick and Wagner A. Vendrame
One of the largest horticultural trade shows in the United States, the Tropical Plant Industry Exhibition, takes place each January in Fort Lauderdale, Fla. The timing of this show coincides with the offering, during the spring semester, of an undergraduate horticulture course, Palm Production and Culture (ORH 4321C, 3 credits). We have developed a guided activity in which we assign the students to visit several preselected exhibits in this show, so that each exhibit in the show is visited by at least one student. The students complete a questionnaire for each exhibit in which they note the identity of the palm species present, the number of species present, the number of individuals of each species, and the total number of palms in each exhibit. Data in the questionnaires are compiled and used to augment and reinforce class discussions on morphology, cultural requirements, interiorscape management, species richness, species diversity, and field laboratory work in morphology and taxonomy. Procedures used have the potential for adaptation to other types of horticultural trade shows and other types of horticultural crops, as well as for other courses in horticulture.