Masters Theses

Date of Award

8-2003

Degree Type

Thesis

Degree Name

Master of Science

Major

Landscape Architecture

Major Professor

William Klingeman

Committee Members

Stephen Garton, Gary McDaniel

Abstract

Dogwoods are one of Tennessee's most important nursery crops. Yet, dogwoods are challenged by several disease and insect pests in production and landscape systems. Powdery mildew and dogwood anthracnose are diseases that severely impact native stands, production fields, and landscape plantings of dogwoods. Researchers at the University of Tennessee have developed the 'Appalachian' series of dogwoods: 'Appalachian Spring is resistant to dogwood anthracnose. 'Jean's Appalachian Snow,' 'Karen's Appalachian Mist,' and 'Kay's Appalachian Blush' are resistant to powdery mildew. Unfortunately, to reproduce the desirable genetic traits found in these trees, these cultivars must be propagated by bud grafting. Low availability of budwood has slowed release to commercial growers and, in turn, the public. Our efforts sought to find an optimum nitrogen fertility rate for budwood production in five commercially important dogwoods. Results indicate that although bud numbers were not affected by fertility treatment, 5.3 kg/m3 (9 lbs/yd3) of Osmocote 18-6-12 yielded optimum shoot growth and caliper in sufficiently irrigated dogwoods. This study also demonstrated that management practices, including proper planting time and water availability, play a crucial role in dogwood performance. Finally, different species and cultivars of dogwood responded differently to higher rates of nitrogen fertility, underlining the fact that growers need to tailor their production practices to the specific species and cultivars that they produce.

Whitefringed beetle larvae (Naupactus leucoloma) girdle roots of young seedling liners. In Tennessee, flowering and kousa dogwood (Cornus florida and C. kousa) have been affected by larval injury. In an attempt to quantify the damaging capacity of whitefringed beetle larvae flowering and kousa dogwoods were infested with 0, 1,3, 6, or 9 larvae and grown for two months in 2002 and again in 2003. Larval damage was most severe in pots with 6 larvae. Young, seedling liners with few lateral and fibrous roots were most affected by larval root injury. Severe root injury resulted in stunted growth and in some cases death of the tree.

Whitefringed beetle adults are parthenogenic. Adult fecundity and longevity are directly affected by host plant leaf tissue. The impact of ornamental food resources on longevity and fecundity of whitefringed beetles has not been assessed. Foliage of 10 common ornamental species, a common weed, and peanut were fed to 360 individually caged whitefringed beetle adults during 2002. Fecundity and longevity were recorded. Kobus magnolia (Magnolia kohus) induced greatest longevity in beetles. Witchhazel (Hamamelis virginiana) and the two dogwood species, which can experience extensive root damage in the field, did not yield high longevity and fecundity in whitefringed beetles. Still, these plants should not be grown near ornamentals that enhance fecundity, like kobus magnolia or yellowwood (Cladrastis kentukea). Infested fields should also be kept free of weeds and high-risk crops should be rotated within a field on three to four year intervals. Inclusion of a cover crop, like sudax, oats, or a small grain or cereal can alleviate populations of whitefringed beetles, while leguminous cover crops, like red clover, should not be planted where whitefringed beetles are a concern. Finally, the presence of adult beetles should be monitored and adults should be targeted with insecticidal sprays as soon as they emerge. Since adults emerge throughout the season, continuous monitoring for adults and possible repeat insecticide treatments will be necessary/

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS