Location: Southern Horticultural Research2010 Annual Report
1a. Objectives (from AD-416)
The objectives are to develop new and improved crop production practices and disease and insect control practices for ornamental, small fruit and other horticultural crops adapted to the U.S. Gulf Coast region. The developed management techniques are needed to minimize production losses and improve crop quality and yield for the purpose of increasing net income.
1b. Approach (from AD-416)
Identify and evaluate nutritional and cultural requirements, non-Apis pollination efficiency, insect pest problems, and plant disease problems to improve orchard establishment, human health benefit, crop yield, and post-harvest quality of fruit crops. Management techniques to be evaluated include planting systems, irrigation systems, fertilizer selection and timing, non-Apis bee colony establishment, suitability of bio-control organisms, pesticide selection and timing, cultivar selection, fruit handling, and post-harvest storage conditions. Identify and evaluate different organic substrates, insect pest problems, and plant disease problems to improve production options and crop quality of ornamental plants. Management techniques to be evaluated include irrigation and nutritional requirements of plants grown in different organic substrates, suitability of bio-control organisms, cultivar selection, pesticide selection and timing, pesticide application technology, disinfestant selection, and sanitation practices.
3. Progress Report
Progress in small fruit physiology research involved identification of nutraceutical components of barely ripe, fully ripe and over ripe berries. Field fertigation studies were established and fertigation begun. Progress in small fruit entomology research included testing the efficacy of three parasitic wasp species to kill blueberry gall midge larvae. Midge larvae populations were reduced by as much as 90%, a mortality rate comparable to that caused by conventional insecticides. Geranium rose oil, a new and very potent source of biological insecticides, had a lethal potency calculated to be 10 times that of Malathion at the same concentration. Two plant growth regulators (Gibberellic acid and Coconut oil), the latter’s effect being accidentally discovered, increased blueberry fruit set by 40 to 100% and could be used to save berry crops experiencing adverse growing conditions. Progress in small fruit plant pathology research included identification of Phytophthora cinnamomi isolates from soil in blueberry fields, a method to screen blueberry resistance to Phytophthora root rot, establishment of blueberry cultivars in a Phytophthora infested field, nitrogen fertilizer effects on muscadine diseases, bumble bee delivery of fungicides and biological agents to reduce blueberry flower blight, screening strawberry germplasm for resistance markers to anthracnose; and establishment of blackberry cultivars to evaluate rosette and orange rust tolerance and to determine incidence and severity of virus diseases. Progress in ornamental horticulture research included demonstrating the versatility of wood-based substrates for crop production. In a fertilizer study, growth of tree and ornamental ginger species was measured in traditional and wood-based substrates. In propagation studies, root growth of five herbaceous and woody perennials was evaluated in whole pine tree (WPT) and pine bark substrates. In the later study, less root development resulted in the WPT substrate. Additional experiments were initiated to identify possible phytotoxicity in WPT substrates. Progress in ornamental plant entomology research involved testing a durable, reusable and illuminated trapping station to efficiently monitor key pest species of moths and strawberry rootworm beetles in nurseries. Progress in ornamental plant pathology research promotes development of an integrated strategy. Scouting protocol is being tested with known temperature and moisture values to determine the early stages of azalea blight development most response to fungicide treatment in nurseries. Research has shown azalea stems used for propagation can be submersed in hot water (122°C) for 20 minutes to eliminate the fungus, Rhizoctonia, without harming plant stems. DNA primers are being tested for specificity to Rhizoctonia AG-P. DNA primers and pathogen culturing will be used to monitor pathogen distribution in the nursery so controls can be developed to prevent spread to clean plants.
1. Azalea Web Blight Routinely Develops in July and August in Ornamental Plant Nurseries, so Understanding the Relationship Between Weather and Disease Development Should Improve Timing of Fungicides. An ARS scientist at Poplarville, MS, and a University of Georgia scientist at Athens, GA, showed a complex interaction exist between moisture and temperature conditions that promote web blight, partly because plants are irrigated daily in nursery production. The information shows timing of the first fungicide spray needed to prevent web blight will require knowledge of favorable weather conditions in combination with simple scouting observations.
2. Binucleate Rhizoctonia Species, the Cause of Web Blight, can be Spread on Azalea Stem Cuttings used to Propagate New Azalea Shrubs. Last year, an ARS scientist in Poplarville, MS, in cooperation with a Mississippi State University scientist in Poplarville, MS, developed hot water treatments that eliminate Rhizoctonia species from azalea stems collected for propagation. This year, twelve evergreen azalea cultivars were successfully rooted after new stem growth was submerged in 122°C water for 20 minutes, which was shown to eliminate the pathogen from stems. Hot water submersion is relatively safe since most cultivars received no to minor damage when submerged for 40 minutes. The control strategy will reduce disease damage, minimize fungicide usage, while improving crop yield potential. The same pathogen causes similar disease problems on multiple other woody shrub genera, such as holly.
3. Development of Effective Methods for Controlling Pest Insects in Containerized Production Systems for Ornamentals. Early detection of insect outbreaks is needed for effective chemical control of multigenerational pests such as the strawberry rootworm, a major root and leaf pest of potted azaleas in large production nurseries. Sticky traps are commercially available for monitoring these beetles, but such cardboard traps are not durable enough with daily pounding from irrigation water in a nursery. ARS researchers at Poplarville, MS have developed and tested a lightweight water-resistant trap station that collects the strawberry rootworm beetle as well as other pest species. Incorporation of a light-emitting diode increased trap catches by 3 to 7 fold for the nocturnal strawberry rootworm. Nursery managers now have a routine monitoring device for detecting early outbreaks of strawberry rootworm and other leaf beetle pests. This station reduces the cost of labor and insecticides as well as eliminates the need for the destructive sampling of plants in order to dislodge adult beetles abruptly from canopies before they can feign death.
4. Phytophthora Root Rot is a Serious Disease of Blueberries Especially Those Grown on Poorly Drained Soils. ARS scientist at Poplarville, MS, conducted four studies to determine the relative susceptibility of 19 southern highbush blueberry cultivars to root rot and to determine the effect of two cultural practices (raised beds and organic soil amendments) on the establishment of these cultivars in soils infested with the root rot pathogen. Most plants of each cultivar tested died within four years of transplanting, and the root rot pathogen was isolated from the roots of most of the plants that died. Neither cultural practice evaluated increased the survival percentage or vigor rating of any of the southern highbush blueberry cultivars. This information will be used by blueberry growers, extension specialists and research scientists making planting recommendations for blueberries in areas where root rot is known to occur.
5. Significant Activities that Support Special Target Populations
Blueberry and muscadine grape plants were donated to the Jackson Public School District for gardens inspired by President Obama. Jackson Public school children will grow, harvest and eat fresh blueberries and muscadine grapes planted at the JPS Environmental Learning Center.
Marshall, D.A., Spiers, J.M., Curry, K.J. 2009. Water Uptake Threshold of Rabbiteye (Vaccunium ashei) Blueberries and its Influence on Fruit Splitting. HortScience. 44(7):1-3 pgs 2035-2037.