Brief Summary of Minutes of Annual Meeting

The research and Extension programs of WERA-058 participants span nursery crop topics from new plant material to production through post-harvest handling to efficient management of landscapes. Researchers in Pennsylvania have identified trees which are not hosts of Anoplophora glabripennis (Asian longhorned beetle, ALB) and on which the adults, eggs, and implanted larvae die while ingesting wood from the trees. In addition, they have evaluated two species, Acer platanoides and Viburnum opulus, for seed production, viability, and germination rate among cultivars as part of evaluating differences in their potential to become invasive. Researchers in Iowa have generated new information on the potential of Rhamnus caroliniana as a shrub or small tree for managed landscapes, including data on its potential as a host for soybean aphid. they also have obtained new information on the genetic relatedness and propagation of the three species of Dirca (leatherwoods) and studied the ecology and genetics of Dirca occidentalis Rhode Island continues to evaluate the growth and marketing requirements of new, sustainable plant species for introduction to the nursery industry. More than 75 trees and shrubs were accessioned in 2004. A collaboration with the URI Master Gardener Program using volunteers and undergraduate students to assessing plant performance has been suspended due to time constraints for the PI. Propagules of all plant materials are made available to cooperating nurseries and arboreta, and to the public on a limited basis. A new research program on the use of low-input plants for roadside planters was started in 2004. Thirty-eight taxa of succulents have been accessioned and grown in replicated mesocosms to investigate suitable growing media and cold hardiness. Rhode Island has continued to research the control of deer in nursery and landscape settings, with the goal of improving plant production and maintenance. Major initiatives include inventories of species preferences for deer rubbing damage in northeast nurseries, and economic impacts of deer damage in the green industry. Several stations are evaluating hardiness, resistance and disease management. Research in Oklahoma is developing methods for controlling anthracnose caused by Colletotrichum gloeosporioides on Euonymus fortunei was continued in the 2004 growing season. Results showed that application of mancozeb continued to reduce anthracnose symptoms, but mancozeb did not eliminate symptoms. Copper sulfate pentahydrate did not reduce anthracnose symptoms. Plants grown with black plastic under containers had slightly fewer symptoms than those grown on gravel, but the difference was not horticulturally significant. Periodic application of 10% bleach solution to the surface of plastic or gravel did not decrease anthracnose symptoms. Pennsylvania has generated new information on the hardiness and arthropod susceptibility of western and asian Tsuga species during evaluation at five climatic and environmentally diverse sites over USDA Hardiness Zones 5 and 6. An Oklahoma study was initiated to evaluate plant growth and winter survival of trees grown above ground in fabric containers compared to those grown in plastic containers. Soil temperatures in the containers were collected at 30-minute intervals throughout the study to determine whether container type affected root zone temperatures. The data are currently being analyzed from this study. Research at Iowa has determined impacts of nitrogen fertilization, root-zone heat, and root-zone oxygen on the formation, development, and function of N2-fixing root nodules on Alnus maritima. New Mexico researchers tested the tolerance to drought and salinity of bigtooth maple (Acer grandidentatum) seedlings from the Intermountain West and Southwest regions to find a plant better suited for southern New Mexico's harsh growing conditions. The Guadalupe Mountains in Texas, the Lost Maples State Park in Texas, and Dripping Springs State Park in New Mexico were identified as provenances that could be used as locations for selecting bigtooth maples for arid environments. Several promising specimens have been selected. The drought responses and water use of Mexican elder (Sambucus mexicana) was evaluated. Mexican elder is a landscape plant that is commonly used in landscapes of the Southwestern United States. Drought-deciduousness is a major drought-adaptation mechanism for Mexican elders. Oklahoma and Ohio researchers are conducting a study with other researchers across the U.S. determining transpiration rates of trees grown in 15-gallon containers. This study was a preliminary study to subsequent research currently in progress that is evaluating plant nutrient use of trees grown in containers using different low pressure drip systems. Research at Rhode Island included the continued development of a 30x100 computer-controlled microirrigation system with 12 independent irrigation zones. All irrigation water applied in this system is recaptured and allows for water quality analysis. This facility is being used to evaluate irrigation methods and container media to optimize low-water use container culture in the northeast. During 2002 and 2003, a cooperative research project was initiated between Texas A&M and the University of Arizona. The project is still in progress and involves a determination of the effects of digging date, cold storage, and cultivar selection on containerized forcing of bare-root garden rose plants. Each year, several million rose plants are harvested bare-root from fields in Arizona and shipped to Texas where they are containerized and grown to bud and bloom for garden center sales across North America. Financial support has been received by nurseries in both locations, and the project was facilitated by participation of scientist from the two university in WERA-058. New Mexico researchers have successfully micropropagated bigtooth maples from greenhouse-grown, two-year seedlings. Tissue culture lines have been established that will be used for further testing. Tissue-cultured material will be distributed to nurseries for propagation and production. Researchers in Missouri and Idaho continue to investigate the use of the Missouri Gravel Bed (MGB). The MGB is a method for handling trees and shrubs that allows bare root plants to be planted throughout the year with excellent survival. In the MGB system, dormant, bare root plants are placed with their roots in frequently-irrigated river rock, containing 10% masonry sand and allowed to develop roots in the rock. MGB was evaluated in MO as a method for preparing planting stock to be grown in containers. Nyssa sylvatica (black gum) and Syringa patula Miss Kim (lilac) plants were evaluated. At the end of the field growing season, root systems of Syringa and Nyssa plants grown in the gravel for a one year prior to potting into 7-liter pots were as large or larger than those grown using the conventional method of potted in smaller pots and overwintered under plastic film covering prior to shifting up to the larger container. Plants that had been fall potted and overwintered in the field in the pot-in-pot nursery were also larger than fall potted plants overwintered under a conventional covering of polyethylene film and 8 mm thick foam blanket. In Idaho corkbark fir and pinyon pine trees seedlings grown in the MGB had larger root systems than those grown in field soil. Although shoot diameters and stem heights were similar for fir or pine seedlings in the gravel bed and field soil, root volumes and dry weights were higher for gravel bed-grown plants than those grown in the field. Pinyon pine seedlings grown in the gravel bed produced at least 37% more root dry weight and 86% more root volume than seedlings grown in field soil. In addition, only about 12% of the pinyon pine seedlings survived when transplanted into the soil, but about 25% of those transplanted into the gravel bed survived. Spruce trees that had all the soil removed from their root systems survived as bareroot trees in pea gravel and basalt gravel. Root systems on all trees regenerated many new fibrous roots. Roots on some of the trees were extensively colonized by mycorrhizae. All trees grew about 8 cm in height despite severe soil loss from their roots. The main leader on about half of the trees died back about 10 cm. Overall, however, the trees survived well. All trees lifted from the gravel beds in September and October survived transplanting to the field (ID).