Monday, December 31, 2007

My Current Research

A number of clientele in Delaware may not be aware that I am in the middle of doing my PhD. I thought I would share a summary of a portion of my research work that could benefit the horticulture industry.

The Potential of Former Poultry House Pad Soils for use as Horticultural Amendments

There are over 2400 derelict poultry houses covering 1000 acres that are out of production on the Delmarva Peninsula. Poultry houses are built over soil pads that accumulate mineral nutrients through diffusion from manure in litter over a 30-50 year period. This includes significant amounts of nitrate nitrogen (NO3-N). Once production ceases, houses are often demolished or left to slowly deteriorate. Exposed pads are subject to leaching from rainfall and high amounts of NO3-N can enter the groundwater. Research is underway to study nutrient loading at these sites and methods to recover nutrients, particularly nitrogen (N). Remediation strategies being explored include co-composting of pad soils to create synthetic soils, use of pad soils directly as a fertilizer, using pad soils for enriched topsoil products, and use of salt tolerant plants as bioremediators that would then be composted. Potential uses of these products as horticultural amendments is a part of this research. Challenges include variability in nutrient content at sites, high salt levels, inconsistency in soil particle sizes, and weight of the material.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Thursday, December 27, 2007

Interiorscape - Interiorscape Plants IV, Ficus

Ficus species are mainstays in interiorscapes. Depending on the species the light requirments vary from low to medium. All ficus species have low water requirements. Some are very sensitive to movement and must be handled gently when placing. They also need to be acclimatized before placing in the interior site. The following are some species and handling requirements.

Images and information from Cynthia McKenney, Texas A&M, Professor of Urban Horticulture and the University of Florida Cooperative Extension.

Landscape - Some Evergreen Tree Species for Kent County Landscapes II

The following are some good evergreen cedars for use in Kent county landscapes as specimen trees or as components of borders, windbreaks, or tall screens.

Information and images from multiple extension and university sources.

Wednesday, December 26, 2007

Greenhouse - Shore Flies and Algae

Shore flies can be a nuisance in greenhouses and have also been implicated in disease spread. Algae control and water management is critical for reducing shore flies as algae is their major food source. The following is an article on the subject.

Shore flies (Scatella stagnalis) thrive in wet areas with algae where they can feed and lay their eggs. Shore flies are often confused with another greenhouse pest found in wet areas, the fungus gnat (Bradysia spp.). Unlike fungus gnats, shore flies have robust bodies, short antennae, spots on their wings, and larvae without head capsules. Shore flies are also stronger fliers than fungus gnats which live mainly on the surface of the soil. Because shore flies do not feed on plant tissues like the fungus gnat, they are considered more of a nuisance pest. However, shore flies are capable of spreading diseases like Pythium.

Eliminating breeding areas and preventing the development of algae in the greenhouse is crucial for managing shore fly populations. Do not allow standing water- especially water containing fertilizer. Practice good sanitation by keeping the greenhouse free of debris. Monitoring for larvae is difficult, but by examining algae covered areas with a good hand lens, you can find the white, wedge-shaped larvae. Monitor adult populations using sticky cards. Control the algae first. If controlling algae alone is not effective in suppressing shorefly populations, then treatments should be directed at the larval stage. Soil drench treatments include: Distance (pyriproxyfen) and Adept (diflubenzuron). Make sure the chemical is applied to a depth of one inch or more. Note: Biological controls such as predatory mites, parasitic nematodes, and Gnatrol (Bacillus thuringiensis) drenches used for fungus gnat larvae are not effective on shore flies.

Several products that can be used to control algae include:

ZeroTol Broad Spectrum Algaecide/Fungicide (hydrogen dioxide product labeled for use both on greenhouse surfaces and on plants)
Physan 20 Algaecide, Fungicide, Bactericide Virucide, (quaternary ammonium compound for use on greenhouse surfaces and on orchids, roses, and African violets)
Green-Shield Algaecide, Fungicide, Bactericide Virucide (quaternary ammonium compound for use on greenhouse surfaces)
GreenClean Granular Algaecide (Sodium Carbonate Peroxyhydrate or use on greenhouse surfaces)
Terracyte Broad Spectrum Algaecide, Fungicide (sodium carbonate peroxyhydrate for use on greenhouse surfaces and on plants)
Triathlon Algaecide, Fungicide, Bactericide (quaternary ammonium compound for use on greenhouse surfaces).

Reprinted from the article "Algae in the Greenhouse Guarantees Shore Flies" in the February 24, 2006 issue of the Greenhouse TPM/IPM Weekly Report from University of Maryland Cooperative Extension.

Landscape - Some Good Evergreen Trees for Kent County Landscapes I

The following are some recommended evergreen trees for Kent County landscapes. Each is adapted to our area and can be used for border, windbreak, and screen plantings as well as for specimen trees in the landscape.

There are many forms of American holly for landscape use from shrubs to large trees. Selections from the Rutgers breeding program have done well as landscape trees in Delaware. They are relatively slow growing but are quite stately when mature.

Oriental spruce is not used as much as other spruces but is worthy of consideration. Skylands is an interesting golden colored form.

Colorado spruces include the blue forms that can be quite dramatic when used properly in the landscape as a specimen plants. They make good border plants too. Fat Albert seen above is perfect for screen use because it has a wide shape that will fill in more quickly.

Norway spruce is a mainstay in northern delaware for a specimen tree, windbreaks, and border plantings. It does not do quite as well on droughty soils downstate but is still a good tree for Kent county.

Concolor fir will grow in Kent county and is a beautify evergreen tree. It is susceptible to some insect problems and should not be planted in high stress sites such as berm plantings. Reserve this tree for sites with good soils with proper drainage and provide water in drought periods. You may need to control mites and bagworms.

Information and images from multiple extension and university sources.

Tuesday, December 25, 2007

Holiday Traditions - Holly and Poinsettias, History and Legends

I came across this article from a county extension office in Kentucky about the history and legends surrounding holly and poinsettias and thought I would share it for the holidays.


Several legends are reported about holly. The ancient Romans considered this plant sacred. Holly was used to honor Saturn, god of agriculture, during their Saturnalia festival held near the time of the winter solstice. The Romans gave one another holly wreaths, carried it in processions, and decked images of Saturn with it. During the early years of the Christian religion in Rome, many Christians continued to deck their homes with holly to avoid detection and persecution by Roman authorities. Gradually, holly became a symbol of the holidays as Christianity became the dominant religion of the empire.

Early Roman Christians believed that the cross on which Christ was crucified was made of holly wood; the crown of thorns was created from holly leaves and the white berries became stained red by Christ’s blood. The white flowers were supposed to represent Jesus’ purity and birth.

During the Middle Ages people associated holly with good fortune. Hollies planted near homes helped protect these homes from thunder and lightning. The berries and leaves were used to ward off witches and evil spirits. It was believed that elves and fairies stayed in the holly and kept the house goblins from causing trouble. The Druids also believed in the protective power of holly, claiming that this was where the woodland spirits took winter refuge.

On the other hand, Medieval Europeans believed family bickering would result if holly entered the home prior to December 24. Holly boughs left up past the New Year would cause one misfortune for each leaf on a branch. (This also correlates with the often-practiced tradition of removing all holiday decorations prior to the New Year, to avoid bad luck.)

Medieval Europeans also believed that picking holly while it was blooming might cause death. However, plucking a piece of holly from church decorations would bring good luck all year long; holly hung in the barn would cause animals to fatten and flourish; and holly picked on December 25 would protect one from witches and evil spirits.

The Germans believed bad luck would befall anyone who stepped on the berries. They also believed that the first person to bring holly into the household each year, rules the household for the coming year.


Another popular plant at this time of year is the poinsettia. These plants are native to Mexico. Originally, these plants were cultivated by the Aztec Indians for their use in dyes and the preparation of fever remedies. This plant was introduced into the U.S. by the first ambassador to Mexico, Joel Robert Poinsett.

One of the most colorful legends associated with poinsettias dates back to ancient Mexico. Legend has it that on December 24, villagers take flowers to the church to the baby Jesus. A young child, too poor to buy flowers, was sad that he had no gift to bring. An angel appeared and told the child to pick some weeds from the roadside and bring them, since any gift given with love would be accepted. As the weeds were placed in the church, the upper leaves of the weed changed into a bright red color. The Mexicans called this weed Flores de nocha buena, or Flowers of the Holy Night. Accounts differ whether it was a girl or boy that delivered the weeds to the church.

Please note: references to particular religions or ethnic groups are not meant to be discriminatory. Information concerning these legends is intended merely for their use in educational value. The University of Kentucky does not endorse nor deny any of these claims. Educational programs of the Kentucky Cooperative Extension Service.

From the Franklin County Kentucky Horticulture Program, Kentucky Cooperative Extension, University of Kentucky

Sunday, December 23, 2007

Landscape - Some Good Trees for Windbreaks, Borders, or Screens in Kent County I

The following are some deciduous or semi-deciduous trees recommended for border, winbreak or screen plantings in Kent county. The species shown below are also good specimen trees for the middle of landscapes. The cultivars when mentioned are more column shaped types suited to massing.

Images and information from multiple extension sources, particularly the University of Florida fact sheet series on tree species.

Interiorscape - Interiorscape Plants III

This is a continuation of the series of plants for interiorscapes. The Dracaena genus gives us a number of very useful plants adapted to low light environments and low water levels.

Images and information from Cynthia McKenney, Texas A&M, Professor of Urban Horticulture and the University of Florida Cooperative Extension.

Saturday, December 22, 2007

Landscape - Some Good Shrubs and Small Trees for Kent County VIII

This is a continuation of the series on recommended plants for Delaware Landscapes. Hollies, both evergreen and deciduous, are mainstays for landscaping. Those below are just a few holly species and varieties to consider.

Images and information from multiple university and extension sources as well as from the National arboretum.

Interiorscape - Interiorscape Plants II, Dieffenbachia

This is a continuation on plants for interiorscaping. Dieffenbachia is another commonly used plant for interiors. It requires medium light exposures and has low water needs.

Images and information from Cynthia McKenney, Texas A&M, Professor of Urban Horticulture and the University of Florida Cooperative Extension.

Friday, December 21, 2007

Landscape - Some Good Shrubs and Small Trees for Kent County VII

This is a continuation of the series on recommended landscape plants for Kent County. The following are some shrubs and small trees that are well suited for our area.

Click on slides for larger images.

Information and images from multiple extension and university sources as well as the National Arboretum.

Greenhouse - Scab on Poinsettia

Scab can be a disease problem on poinsettia. Fortunately it does not show up each year. The following is an article on this disease.

Scab is a type of fungal disease called a “spot anthracnose”, which means that the pathogen, Sphaceloma poinsettiae, will cause tiny round spots and will be splashed about to start new infections if leaves sit wet for long periods. The disease does not appear to be widespread this year, but it is a good idea to review the symptoms so that you can keep a watchful eye on your crop.

Although scab can cause alarm because it is unfamiliar—it is not a disease that occurs every year without fail (like Botrytis!)—it is actually very nicely controlled via fungicides and cultural adjustments. The trick is to notice that it is present in the crop, so that the diseased plants may be promptly rogued out and the neighboring plants treated for their protection.

Often it is the growing areas with the highest amounts of leaf wetness where scab disease symptoms appear. Long periods of leaf wetness are needed for infection. Adjusting cultural procedures so as to reduce the length of time the foliage sits wet is important: water early in the day, use fans strategically and heat and ventilate at sunset to avoid condensation.

Among the fungicide choices, strobilurins such as Heritage and Compass alternated with Eagle, Terraguard or Strike is a strong program that conveniently guards against powdery mildew and gives some Botrytis suppression. Mancozeb-containing materials are effective but may leave high residue, so these should be used at early stages of production.

The symptoms of scab are very striking. The spots are light-colored, small, round, and blistered out from the leaf surface; often they run down a vein. There is usually a yellow halo around each spot. The fungus also infects stems, where it causes larger raised whitish oval “scabs”. Eventually these stem lesions turn brown, after the spores have matured. The most peculiar scab symptom of all is seen on plants that have stem infections, or else extremely heavily infected leaves. The shoots that have these symptoms will hyper-elongate, so that they stretch up several inches higher than the rest of the crop. This effect is due to the plant growth hormone produced by the invading fungus!

Raised oval lesions form on stems as well.

Poinsettias with scab lesions on the stems will hyperelongate. Here the (normal height) plant at the right had only moderate leaf infection, while the one on the left had “scabs” on the stem as well. Photos: Maria Tobiasz

Article extracted from "Scab on Poinsettias Again This Season" by Margery Daughtrey, Cornell University Dept. of Plant Pathology, LI Horticultural Research & Extension Center in the October 2005 edition of Northeast Greenhouse IPM notes.

Thursday, December 20, 2007

Landscape - Some Good Shrubs and Small Trees for Kent County VI

This is a continuation of a series on recommended plants for Kent County landscapes. The following are some small trees and shrubs that are well adapted to our landscapes.

Information and images from multiple university and extension sources.