June 2001


From Ken:

At a recent visit to McCorkles Nursery and the CANR, I found their latest results issue of the research they are conducting at the Center. Below are some highlights from the report. This is a special resource for the nursery industry. The CANR does good practical research to answer the questions and concerns that you have related to your nursery. They have a field day each fall to present and answer questions about the results. We are participating in the research because we believe in and strongly support their efforts to serve the nursery industry. The staff and employees at McCorkles Nursery also make it easy to get research done. I hope you will support their efforts to serve you. If you want the complete article of any of the items reviewed below, send us an email with your name and address.


The following articles are featured in this month's Something to Grow On:

NEW BOOK ON DISEASES OF WOODY ORNAMENTALS AND TREES IN NURSERIES

A YEAR OF DISEASE POSSIBILITIES

PRUNING FOSTER HOLLY

DECREASING pH ON GLORY BLUE HYDRANGEA

EVALUATION OF Abelia grandiflora 'Edward Goucher' FOLIAGE YELLOWING

ABELIA'S COLD HARDINESS

Loropetalum chinense AND L. chinense VAR. rubrum EVALUATIONS

HERITAGE FOR THE CONTROL OF CERCOSPORA NEEDLE BLIGHT OF LEYLAND CYPRESS

PLANT PATHOLOGY REPORT

UPCOMING EVENTS


DISCLAIMER: Please remember that all information presented is a summary of research and not an endorsement of any product or a recommendation of chemicals. The official labels from the manufacturing companies offer the legal and proper use and handling information for all products.


NEW BOOK:
DISEASES OF WOODY ORNAMENTALS AND TREES IN NURSERIES

(Edited by Ronald K. Jones and D. Michael Benson)

A new book published by The American Phytopathological Society, Diseases of Woody Ornamentals and Trees in Nurseries, may be of value to nursery owners. We haven't seen the book yet but this is what the promotional pamphlet states:

"Use the up-to-date information in this new manual to maintain and grow healthy nursery plant stock. The book address the diagnosis and control of more than 65 ornamental crops (shrubs, ground covers and shade trees) grown in nurseries throughout the United States.

A summary of timely control measures is given for each disease in this book. These control strategies provide an in-depth guide to integrated disease management including cultural control, sanitation, resistance, fungicides and bactericides as well as information on control of various pathogen groups. Many of the crop chapters include information on cultivar resistance to plant disease. The role of recycled water in disease development and ways to manage pathogens in recycled irrigation water is also covered. Colored plates illustrate disease symptoms, tissue culture techniques to eliminate pathogens from propagation stock, a state-by-state list of disease occurrences to make you aware of local problems, and an explanation of the role of plant diagnostic clinics in assisting nurseries in disease diagnosis.

The book may be used by anyone involved with the care of valuable plants including nursery professionals, extension specialists, county agents, growers, tree-care professionals, master gardeners, researchers, educators, and regulatory personnel."

The price of the book is $89 and can be ordered on line at http://www.shopapspress.org


A YEAR OF DISEASE POSSIBILITIES

We have been publishing the Extension Plant Pathology Report in our newsletter for a few years. It now seems more prudent to add another page to our website where this information could be easily accessed for each month of the year. Instead of having to go back through archived newsletters to find the relevant month, you can just go to one page. Diseases in the region don't change very much from year to year so it isn't really necessary to keep publishing very similar reports year after year. Go to the Disease Reports button on the home page:

We will continue to publish the timely monthly reports from Auburn and Birmingham Labs in Something to Grow On.


PRUNING FOSTER HOLLY

Foster holly is traditionally pruned at least once a year to contain its rapid growth and to maintain desired shape. Four pruning methods were examined in this study:

  1. cutting branches back 6 inches or at least five nodes
  2. cutting back brances 10" or at least 10 nodes
  3. painting on Promalin (a combination of benzyladenine and gibberellin) mixed with latex paint twice during the growing season
  4. standard pruning two times during the production season
It was observed that pruning at the tips of young plants does not result in fuller plants, while pruning deeper into the heavier wood produces several breaks on the stems resulting in fuller and tighter growth.

Results indicated that the standard treatment of pruning twice a year to desired shape produced the best quality plants. Promalin didn't produce bud breaks or initiate new branching.

(from "Pruning Foster's Holly" by Dr. James T. Midcap, University of Georgia, 2000 Research Reports published by the Center for Applied Nursery Research).


DECREASING pH ON GLORY BLUE HYDRANGEA

To achieve the blue bract color on Hydrangea macrophylla a pH of 5.5 or less is required along with the availability of aluminum. The addition of aluminum sulfate to the soil is required. Variables in this process, though, are the amount of lime in potting mixes, the quality of irrigation water, and the source and rate of applied fertilizer.

This research project determined that the addition of 1.5 oz. of aluminum sulfate per gallon pot appears to be adequate to achieve the desired results unless the pH is very high. Great care must be taken in the application of higher levels of aluminum sulfate as that can result in very stressed plants. Consequences would be plant stunting, some leaf drop and smaller flowers.

(from "Decreasing pH on Glory Blue Hydrangea" by Dr. James T. Midcap, University of Georgia, 2000 Research Reports published by the Center for Applied Nursery Research).


EVALUATION OF Abelia grandiflora 'Edward Goucher' FOLIAGE YELLOWING

Abelia x grandifolia 'Edward Goucher' often becomes yellow and unsalable during the production season. Chlorotic yellow Abelias responded to being top dressed with iron chelate at the 1.2 teaspoon (3 g) rate. The application of lime, fertilizer and foliar sprays of micro-nutrients helped in growing Abelias in the nursery. Micromax and lime treatments positively affected height and width of Abelia plants. 4# and 8# lime treatments produced the largest plants while the 0# lime treatment produced the smallest plants. The 0# and 0.75# Micromax treatments produced the largest plants, while the 1.5# Micromax treatment produced the smallest plants. The addition of 4# and 8# lime increased the potting mix nutrient levels of NO3, potassium, calcium and magnesium over the 0# lime rate. There was no benefit of applying the 8# lime rate, which would be more expensive. The 1.5# Micromax treatment reduced the available nutrient levels for the 4# lime treatment.

(from "Evaluation of Abelia grandifolia 'Edward Goucher' Foliage Yellowing" by Dr. James T. Midcap, University of Georgia, 2000 Research Reports published by the Center for Applied Nursery Research).


ABELIA'S COLD HARDINESS

Abelia is a popular, attractive landscape plant which has lovely small flowers, compactness and adaptabilty to landscape stresses. The leaves of Abelia x grandiflora are dark and lustrous and evergreen (semi-evergreen in northern climates). What is problematic about the plant is that its lack of cold hardiness affects stem and leaf hardiness and thereby limits how far north it can be distributed. Freeze damage on plants is a major concern for growers, even in subtropical regions. Twelve Abelia taxa were evaluated to determine the lowest survival temperatures. The greatest stem hardiness was found to be in Abelia chinensis, Abelia x grandiflora and Abelia zanderi (all survived to -13 degrees F). 'Edward Goucher', 'Golden Glow', and 'Rostrata' had the least hardy stems (survived to 1 degree F).

(from "Evaluation of Abelia Taxa for Cold Hardiness Potential" by S.M. Scheiber, O.M. Lindstrom, C.D. Robacker, and M.A. Dirr, University of Georgia, 2000 Research Reports published by the Center for Applied Nursery Research).


Loropetalum chinense AND L. chinense VAR. rubrum EVALUATIONS

The following 14 selections were observed relative to leaf coloration in sun and shade. Moderate water and fertilizer are the keys to foliage coloration. Plum Delight and 'Zhuzhou Fuchsia' have the best red-purple coloration:

KEY: 1= green, 5=red/purple

GREEN LEAF TYPES
'Compact'11
'Snow Dance'11
'Species'11

RED LEAF TYPES (var. rubrum)
'Blush'1.502.25
'Bicolor'1.502
'Burgundy'33.50
Fire Dance43.50
Pipa's Red4.504.25
Plum Delight4.505
'Ruby'44
'Sizzling Pink'43
'Suzanne'3.503.50
'Variegata'1.251.50
'Zhuzhou Fuchsia'4.504.50

Fast growing, large forms: Fire Dance, Pipa's Red, 'Zhuzhou Fuchsia'
Slower growing, more compact forms: 'Ruby', 'Suzanne'
Green selection of note: Snow Dance with smaller habit and foliage, excellent garden potential

(from "Loropetalum chinense and L. chinense var. rubrum evaluations" by M.A. Dirr, University of Georgia, 2000 Research Reports published by the Center for Applied Nursery Research).


HERITAGE FOR THE CONTROL OF CERCOSPORA NEEDLE BLIGHT OF LEYLAND CYPRESS

The defoliation of Leyland Cypress by Cercospora Needle Blight is a perennial problem for growers and homeowners. Yellow, dropped needles very negatively affect the appearance of the plant.

Plants were evaluated by visual examination of how much of the plant canopy was affected by the disease based on the amount of needle drop on lower branches. Needle blight infection was determined by averaging the total number of new infection sites within a six inch section of the previous year's growth on three randomly selected lower branches of each tree.

The fungicide treatments of Heritage (4 oz. and 8 oz/100 gal), Systhane and Cleary's 3336 resulted in significantly lower defoliation ratings than the Heritage at 1 oz. and 2 oz/100 gal rate and the untreated plants. Although infections following Systhane and Cleary's 3336 applications were lower than the untreated plants, the difference was not significant. Application of Heritage at 4 oz. and 8 oz/100 gal rates provide the best numerical disease reduction with less than four new infections occurring on the preivous year's growth.

(from "Evaluation of Heritage for the control of Asperisporium (Cercospora) Needle Blight of Leyland Cypress" by Dr. Jean L. Williams-Woodward, University of Georgia, 2000 Research Reports published by the Center for Applied Nursery Research).


EXTENSION PLANT PATHOLOGY REPORT

APRIL PLANT DISEASES FROM THE
AUBURN AND BIRMINGHAM PLANT DIAGNOSTIC LABS

Jackie Mullen, Extension Plant Pathology Specialist-Auburn
Jim Jacobi, Extension Plant Pathology Specialist-Birmingham

Auburn Plant Disease Report
April (J. Mullen)

April was a good month for seasonal spring temperatures and adequate rainfall in much of the state with the exception of some southern sections of the state. Our sample numbers in the lab increased dramatically from March with abiotic problems outnumbering the biotic diseases at a 4:1 ratio! Many of the abiotic problems involved diebacks we believe relate to drought situations of last summer and fall.

Azalea diseases seen included Phytophthora foliage blight, Colletotrichum leaf spot and powdery mildew. Phytophthora foliage blight appears as leaf spots/blight and dieback. Positive confirmation of Phytophthora usually requires culture work or ELISA testing. Disease control involves sanitation (removal of infected plants). Protective fungicide treatments are recommended in nursery situations. See ANR-571 or the Alabama Pest Management Handbook for specific fungicide recommendations. Phytophthora may develop as Crown/root disease or foliage disease, depending upon the specific species involved and the plant situation. Phytophthora may be a problem when conditions have been wet for a prolonged period of time. Colletotrichum leaf spot on azalea develops as circular dark brown or black spots, about 2-3mm diameter. This disease is controlled by removal of all fallen leaves and application of protective fungicide treatments. See the Alabama Pest Management Handbook for current fungicides available. Powdery mildew on azalea usually develops in the spring or fall when moderate temperatures and high humidity conditions exist. In many situations disease does not develop to a significant extent. If disease continues to develop and humidity levels remain high in the foliage canopy, protective fungicides may be used.

Black rot on crabapple was diagnosed on the basis of the presence of Botryosphaeria obtusa fruiting bodies developing on cankers. In the spring, spores from the cankers and fruit mummies will infect developing leaves and fruit with leaf spots and fruit rot developing in May and June-July. Pruning of cankers in early spring is recommended, making cuts 3-5 inches beyond the canker margins. All fallen leaf debris and fruit mummies should be removed from the area before spring growth begins. If disease has been a problem in the past, protective fungicide sprays may be applied throughout the growing season. See the Alabama Pest Management Handbook, Vol. 1 (commercial) or ANR-50 (homeowner) for current recommendations.

Fireblight, caused by the bacterium Erwinia amylovora, is a problem on pears and apples every spring. When a late cold event occurs, fireblight is often more of a problem as the bacteria will enter cold-damaged plant tissues. Bacteria overwinter in cankers of infected trees, and insects and splashing rain will move bacteria to blossoms where most infection takes place. Streptomycin sprays on healthy blossoms will prevent blossom infections. Once the bacteria become established in the flowers, disease will spread into branches causing dieback that develops quickly. Once trees become infected, severe pruning is the only control method available. Pruning cuts should be made 10-14 inches beyond the canker margin.

Entomosporium leaf spot on photinia is typically a serious disease. Red-black leaf spots develop profusely on upper and lower leaf surfaces when temperatures are between 55F and 80 and leaf surfaces are wet. Severe pruning, clean-up of all fallen leaves, and regular fungicide sprays during spring and fall will help control this disease. Spotted leaves will drop. Shrub replacement is often the most practical recommendation.

Downy mildew of rose usually begins with yellow spots with indefinite margins. When conditions are cool and humid, the thin gray fungal growth of downy mildew will develop on lower leaf surfaces of the spots. As spots age, they become dark brown. Downy mildew may be difficult to confirm sometimes as it is an obligate parasite (We are not able to grow it out in culture.).

Cercospora leaf spots are common on turnips and other related plants during March and April. Spots are typically a light brown, cream, or white with irregular shapes. Spores of the fungus are usually observable with microscopic study. Sanitation and crop rotation will usually help control this disease. See the Alabama Pest Management Handbook for fungicide recommendations.

Brown patch has been diagnosed in several situations on centipede and St. Augustine grass this past month. Cultural modifications (nitrogen and thatch) and application of protective fungicide treatments are usually necessary for control of this disease. Fungicide treatments should be applied 3-4 times, according to label directions, for good disease control. See the Alabama Pest Management Handbook and ANR-492 for specific fungicides.

The take-all fungus was observed on several St. Augustine samples and on one centipede sample. See ANR-823. The relationship of this fungus disease to environmental stress is not completely understood. Preliminary attempts to reproduce take-all patch in a greenhouse situation have not been successful. Recommendations remain as they have been described in ANR-823. Long term control requires soil pH be kept about 6.0. Higher pH levels will stimulate fungal development. Also, nitrate fertilizers should be avoided since they are known to encourage fungal development. A third environment factor known to stimulate fungal activity is moisture. Frequent, short showers or irrigations are known to cause increased disease development. Fungicides recommended to control take-all are expensive, and their use is not practical for many homeowner situations. Reports indicate that these fungicides may not always provide 100% disease control.

A rust disease caused by Puccinia hemerocallidis, new to the U.S., was found on daylilies in some southeastern nurseries last summer. USDA and APHIS pathologists and mycologists and state agriculture pathologists and inspectors are watching for more occurrences of this disease this year. The rust has been confirmed in nurseries in Alabama, Florida, Georgia, and South Carolina. Foliage is severely damaged by the infection. The characteristic rust pustules develop and leaves will then become necrotic. The rust has been reported on the following varieties of daylily: Pardon Me, Gertrude Condon, Starstruck, Stella D'Oro, Joan Senior, Colonel Scarborough, Crystal Tide, Imperial Guard, Double Buttercup, and Attribution. Pardon Me is reported to be the most susceptible. If you think you may have seen this disease, send a sample for confirmation to the Plant Diagnostic Lab at Auburn or Birmingham. If the sample appears to be rust, we will send it on to USDA mycologists in Beltsville, MD for confirmation. The alternate host for this rust disease is the perennial Patrinia spp. which is grown in the U.S. as an ornamental. So far rust disease has not been detected on this plant.

2001 APRIL PLANT DISEASES SEEN IN
THE PLANT DIAGNOSTIC LAB AT AUBURN
PLANTDIAGNOSISCOUNTY
AzaleaColletotrichum Leaf SpotDeKalb
AzaleaPhytophthora Foliage Blight *
AzaleaPowdery MildewMontgomery
AmaryllisStagnospora Leaf SpotGeneva, Montgomery
CrabappleBlack Rot (Botryosphaeria)Montgomery
DianthusAlternaria Leaf SpotEscambia
DogwoodBotrytis Blossom BlightMontgomery
ImpatiensColletotrichum Leaf SpotDeKalb
LiriopeFusarium Root DecayCalhoun
PhotiniaEntomosporium Leaf SpotLee
RoseDowny Mildew (Peronospora) *
RoseVirusCalhoun
*County locations for nursery/greenhouse problems are not reported.

Birmingham Plant Disease Report
April (J. Jacobi)

The Birmingham lab had its busiest month since opening last year. We logged in 81 samples last month, compared with 29 in April 2000. Brown patch was the most common disease on turfgrass, with several samples on zoysiagrass and two samples from hybrid bermudagrass (less common). The patches on the bermudagrass ranged in size from 3 feet to nearly 20 feet in diameter. Refer to ANR-472, " Controlling Brown Patch on Warm-Season Turfgrasses in Home Lawns", for a detailed description on controlling brown patch. One of the more interesting diseases seen last month was an unidentified fungal leaf spot (possibly Cercospora spp.) on the perennial Gaillardia.

2001 APRIL PLANT PROBLEMS SEEN IN
THE BIRMINGHAM PLANT DIAGNOSTIC LAB
PLANT DISEASE/INSECT PROBLEMCOUNTY
AzaleaPythium Root RotJefferson
AzaleaPhomopsis DiebackJefferson
AzaleaPhytophthora Root RotJefferson
AzaleaAzalea Petal BlightJefferson
Boxwood, AmericanVolutella BlightJefferson
Boxwood, AmericanPhytophthora Root RotJefferson
Boxwood, EnglishMacrophoma Blight (2)Jefferson
Boxwood, EnglishBoxwood Leaf Miner
Boxwood, EnglishVolutella BlightJefferson
Camellia, SasanquaDieback/AnthracnoseJefferson
DianthusAlternaria Leaf SpotJefferson
GaillardiaFungal Leaf SpotJefferson
Holly, Japanese 'Compacta'Black Root Rot
(Thielaviopsis spp.)
Jefferson
Indian HawthorneEntomosporium Leaf SpotJefferson
Juniper, Blue PacificPhytophthora Root RotJefferson
Maple, FloridaAnthracnoseSt. Clair
Maple, JapaneseAnthracnose Shelby
Oak, BlackHypoxylon CankerShelby
PansyPythium Root and Crown RotJefferson
PoinsettiaPowdery MildewJefferson
Privet, variegatedPrivet Rust MiteJefferson
SycamoreAnthracnoseJefferson

UPCOMING EVENTS

June 20 - 23, 2001:
2001 Southeast Greenhouse Conference and Trade Show.
Greenville, SC.
For more information call 877-927-2775; www.sgcts.org

July 24 - 28, 2001:
Cullowhee Conference: Native Plants in the Landscape.
Western Carolina University in Cullowhee, North Carolina
For more information call 770-922-7292.

August 2-5, 2001:
SNA 2001 - Southern Nurserymen's Association Researcher's Conference and Trade Show.
Georgia World Congress Center, Atlanta, GA. Contact SNA at 770-973-9026; SNA Infoline at 770-973-4636;
http://www.sna.org

September 30 - October 3, 2001:
Eastern Region International Plant Propagators' Society Annual Meeting.
Lexington, KY. Contact Margot Bridgen, 26 Woodland Road, Storrs, CT 06268; phone 860-429-6818; e-mail mbippser@neca.com

October 12-13, 2001:
Middle Tennessee Nursery Association Horticultural Trade Show.
McMinnville Civic Center, McMinnville, TN
phone: 931-668-7322; fax: 931-668-9601; e-mail: mtna@blomand.net,
http://www.mtna.com or http://www.tnnursery.com/mtna

October 18-21, 2001:
Southern Region International Plant Propagators' Society.
Houston, TX. Contact David Morgan at 817-882-4148; fax: 817-882-4121; SR IPPS, P.O. Box 1868, Ft. Worth, TX 76101; e-mail: dmorgan@bsipublishing.com

November 30 - December 1, 2001:
The Great Southern Tree Conference.
Contact Heather Nedley at hnedley@fnga.org; 1-800-375-3642.

October 11-12, 2002:
Middle Tennessee Nursery Association Horticultural Trade Show.
McMinnville Civic Center, McMinnville, TN
phone: 931-668-7322; fax: 931-668-9601; e-mail: mtna@blomand.net,
http://www.mtna.com or http://www.tnnursery.com/mtna

April to October, 2002:
Floriade 2002.
See the AmeriGarden (5,400 square feet), part of the world horticulture exhibition in the Netherlands.
For more information call 808-961-6660 or visit http://www.floriade.nl or http://www.amerigarden2002.com

Send horticultural questions and comments to ktilt@acesag.auburn.edu.

Send questions and comments to bfischma@acesag.auburn.edu.

Letters to Bernice Fischman - 101 Funchess Hall - Auburn University, AL 36849.