by Mathews Paret | Mar 25, 2014
Figure 1. Witches’ broom like appearance, abnormal red discoloration of shoots and foliage, excessive thorns, distorted leaves, and deformed buds and flowers are key symptoms for the devastating Rose Rosette Disease
Roses are one of the most popular flowering shrubs in U.S. with a total wholesale value of 194 million U.S. Dollars. Among the major states in U.S., Florida is the fourth largest producer of roses with a total value exceeding 20 million U.S. Dollars. Among the major diseases on roses, Rose Rosette Disease caused by Rose Rosette Virus (RRV), an Emaravirus has been a major problem for roses in many states in the U.S during the last many years. This virus is spread by an eriophyid mite species Phyllocoptes fructiphilus. This disease was not present in Florida until November 2013, when the disease was first discovered and now confirmed in 3 Florida counties, which include one in the Panhandle. On Wednesday March 19, Horticulturists from throughout the South met at the NFREC in Quincy Florida to discuss detection and control measures that might be used to combat this viral disease.
Figure 2. Severe thorn proliferation is another characteristic of rose rosette disease.
The key symptoms for Rose Rosette Disease include witches’ broom, excessive thorns, abnormal red discoloration of shoots and foliage, distorted leaves and deformed buds and flowers (click the link below for symptoms). The diseased plants usually die in 1-3 years. Considering the economic importance of the rose plants, and the highly destructive nature of the Rose rosette virus, research is currently underway by scientists at the University of Florida and the Division of Plant Industry-FDACS to develop early detection methods for the virus and management practices. This project is funded by Florida Nursery Growers and Landscape Association, and the University of Florida, IFAS Dean for Research.
Figure 3. Distorted flower bud; leaf developing from flower bud tissue.
Figure 4. Severe yellowing and stunting of the plant. Infected plants usually die in 1-2 years.
How Home Gardeners and Landscape Professionals Should Respond:
-
Routine scouting and early identification. Submit samples for definitive confirmation.
-
Destroy infected plants. There is no cure for rose rosette disease. Detection will prompt a quarantine by DPI until cleaned up.
-
Eriophyid mite management in early spring is not necessary right now since it has not been found in Florida.
-
Note: The Eriophyid mite species described as the vector for RRV is not known to be present in Florida. Thus mite management recommendations are protective in nature.
Further details can be found in the links below.
U-Scout Pest Alert
by Matthew Orwat | Mar 18, 2014
March may seem a little early to worry about fungal diseases, but recent prolonged wet weather and warmer temperatures have made the climate just right for a variety of leaf diseases in the Florida Panhandle. One in particular, Blackspot (Diplocarpon rosae), is particularly problematic for the discerning rose grower. Blackspot is just beginning to be seen this season on non-resistant rose cultivars throughout the central Florida panhandle.
Monsieur Tillier, a rose that shows promise for blackspot resistance, is also part of the Earthkind program. Image Credit Matthew Orwat
Blackspot spores are spread from the canes or leaves of the previous season’s growth by rain or overhead irrigation. To minimize innoculum (black spot spores) remove all leaves from the previous season and any dead leaves at the base of the plant. After the annual pruning in mid to late February, it is a good idea to spray roses with sulfur or copper based fungicidal soap. This helps kill spores that have been laying dormant throughout the winter. Be careful not to spray these products when temperatures rise above 80 ° F. Doing so could burn the plants, although these products will damage tender young growth as well at temperatures below 80 ° F .
Wet, blackspot affected leaves. Image Credit Matthew Orwat
While dormant sprays often allow rose gardeners to get ahead of the disease, the best defense for the home garden is to plant resistant cultivars. There are several old and new resistant cultivars on the market. Some new resistant cultivars of note include Home Run and Knockout. Also, several older cultivars have demonstrated excellent resistance, such as Mrs. B.R. Cant and Spice. The author has been working with several older rose cultivars at the UF / IFAS Washington County Extension demonstration garden that have shown resistance during the last three years. While this demonstration garden is not a scientific study, several roses that have demonstrated some merit include Belinda’s Dream, Monsieur Tillier, Mme. Antoine Mari, Rosette Delizy and Souvenier de la Malmaison. Another resource for information on disease resistant roses is the Texas Earthkind rose program from Texas A&M University. While disease resistance is not always identical in different parts of the county, their recommended list gives the beginning rose gardener a good place to start.
Mrs. B. R. Cant, a tea rose from 1901 has shown very good blackspot resistance at the UF IFAS rose trials in Quincy, FL. Image Credit Matthew Orwat
Several other cultural methods that will prevent spread of this disease among the rose garden include avoiding overhead irrigation, planting in well ventilated areas and proper plant spacing. These techniques attempt to make the garden environment inhospitable for blackspot proliferation.
Regardless if these management techniques are followed, if traditional large, long-stemmed, high maintenance Hybrid Tea roses are desired, most Florida rose gardeners will need to begin a spray schedule to prevent the onslaught of blackspot. Several fungicides are on the market to aid in this process, but remember that they must be used regularly (every 7-14 days) and modes of action must be rotated. This means that different types of fungicide must be rotated so that resistance to a particular fungicide by the blackspot organism does not develop. Below is a table of recommended fungicides for homeowner blackspot control. For more information, please consult the UF IFAS Extension publication P268, Blackspot of Rose.
Fungicide products marketed toward homeowners for control of black spot on roses
|
Active ingredient
|
Fungicide group
|
Trade name
|
|
Copper hydroxide
|
M1
|
Hi-Yield ® Copper |
|
Copper Sulfate
|
M1
|
Bonide® Copper Dust |
|
Copper Octanoate
|
M1
|
Bonide® Liquid Copper, Natural Guard Copper Soap, Ortho® Disease B Gon® Copper Fungicide |
|
Sulfur
|
M2
|
Bonide® Sulfur Dust, Ferti-lome® Dusting Sulfur, Green Light, Hi-Yield® Dusting Wettable Sulphur, Ortho® Bug-B-Gon® Rose & Flower Care |
|
Mancozeb
|
M3
|
Bonide® Mancozeb |
|
Captan
|
M4
|
Bonide® Captan 50WP, Hi-Yield® Captan 50W Fungicide |
|
Chlorothalonil
|
M5
|
Bonide® Fungonil, Ferti-lome® Broad Spectrum, Hi-Yield® Vegetable, Flower, Fruit and Ornamental Fungicide, Monterey, Ortho® Disease B Gon™ Garden Fungicide , Monterey Fruit Tree, Vegetable & Ornamental Fungicide |
|
Myclobutanil
|
3
|
Spectracide Immunox® Multi-Purpose Fungicide |
|
Propiconazole
|
3
|
Ferti-lome® Liquid Systemic Fungicide, Monterey Fungi-Fighter |
|
Tebuconazole
|
3
|
Bayer Advanced™ Disease Control for Roses, Flowers & Shrubs |
|
Tebuconazole + Imidacloprid
|
3 +
|
Bonide® Rose RX Systemic Drench, Feti-lome® 2-N-1 Systemic |
|
Triforine
|
3
|
Ortho® RosePride® Disease Control |
|
Calcium Polysulfide
|
NC
|
Hi-Yield® Lime Sulfur Spray |
|
Neem Oil
|
NC
|
Bonide® RX 3 in 1, Green Light® Neem Concentrate, Green Light® Rose Defense®, Monterey |
|
Acetamiprid + Triticonazole
|
NC + 3
|
Ortho® Bug B Gon® Insect & Disease Control |
|
Acephate + Resmethrin + Triforine
|
NC + NC + 3
|
Ortho® RosePride® Insect, Disease & Mite Control |
| Fungicide Group (FRAC Code): Numbers (1-37) and letters (M) are used to distinguish the fungicidal mode of action groups. All fungicides within the same group (with same number or letter) indicate same active ingredient or similar mode of action. This information must be considered in making decisions about how to manage fungicide resistance. M=Multi-site inhibitors, fungicide resistance is low; NC= not classified. Source: http://www.frac.info/ (Fungicide Resistance Action Committee, FRAC).
Always read a current product label before applying any chemicals.
|
by Gary Knox | Mar 18, 2014
Given crapemyrtle’s reputation for plant vigor and pest resistance, I was shocked to see Chinese crapemyrtles noticeably affected by a previously obscure pest.
Last November I had the privilege of traveling to China with Dave Creech (Stephen F. Austin University), Mengmeng Gu (Texas A&M) and Yan Chen (LSU-Hammond). Crapemyrtles, Lagerstroemia spp., are native to Asia, and China is regarded as the first to cultivate crapemyrtle as a flowering tree. As a crapemyrtle enthusiast, I eagerly looked forward to seeing Lagerstroemia collections in Chinese botanical gardens. What we saw in Beijing surprised us.
![Figure 1 Note the black sooty mold coating the layers of white and grey scale, believed to be crapemyrtle bark scale, Eriococcus lagerstroemiae. [Photo by Gary Knox in Beijing, China]](https://nwdistrict.ifas.ufl.edu/hort/files/2014/03/crapemyrtle-scale-768x1024.jpg)
Figure 1 Note the black sooty mold coating the layers of white and grey scale, believed to be crapemyrtle bark scale, Eriococcus lagerstroemiae. [Photo by Gary Knox in Beijing, China]
Symptoms, Appearance and Distribution in China
An early symptom of crapemyrtle bark scale is black sooty mold covering extensive areas of leaves and stems as a result of honeydew exuded by the scale. Individual scale insects are white to gray in color and ooze pink when crushed (Fig. 2). Large populations build up in branch crotches and extend up branches, appearing crusty white to gray. This scale usually is not present on new growth, leaves or slender stems unless infestations are heavy.
![Figure 2. This white to grey colored scale oozes pink when crushed. [Photo by Gary Knox in Beijing, China]](https://nwdistrict.ifas.ufl.edu/hort/files/2014/03/crapemyrtlescale2-505x1024.jpg)
Figure 2. This white to grey colored scale oozes pink when crushed. [Photo by Gary Knox in Beijing, China]
We found this scale on crapemyrtle in all four cities we visited, across hardiness zones roughly equivalent to USDA Cold Hardiness Zones 6b to 9 (Beijing, Zone 6b/7a; Nanjing, Zone 8a/8b; Shanghai, Zone 8b/9a; and Kunming, Zone 9). However, this scale was not found on all crapemyrtle. My personal observation is that stressed plants appeared more susceptible to this scale, as exemplified by infestations on freeze-damaged crapemyrtle in Beijing (Fig. 3) or in a poorly maintained planting in the Nanjing Airport parking lot. Our hosts indicated the problem appeared to be more severe on hybrid cultivars introduced from the U.S., and our observations mostly confirmed that.
In the U.S.?
Unfortunately, crapemyrtle bark scale or a similar scale may already be in the U.S. A new scale insect believed to be a species of Eriococcus was first discovered in the Dallas, Texas, area in 2010 where it is problematic on landscape crapemyrtles. It has not been definitively identified by entomologists yet and management recommendations are still being developed. However, this scale has since been observed in Shreveport, LA, Memphis, TN, and Little Rock, AR, undoubtedly being moved with plants. The expanding distribution of this scale and my personal observations of crapemyrtle bark scale throughout China suggest this scale could have a widespread and severe impact on crapemyrtles in landscapes.
![Figure 3. Dr. Gu is dismayed at seeing this crapemyrtle planting infested by scale (note the black sooty mold on stems). [Photo by Gary Knox in Beijing, China]](https://nwdistrict.ifas.ufl.edu/hort/files/2014/03/crapemyrtlescale3-767x1024.jpg)
Figure 3. Dr. Gu is dismayed at seeing this crapemyrtle planting infested by scale (note the black sooty mold on stems). [Photo by Gary Knox in Beijing, China]
by Taylor Vandiver | Feb 25, 2014
Considering it is the month of Valentine’s, roses are an appropriate subject to discuss. Not bouquets couriered to various locations all over town, but bushes in the landscape that have been strategically neglected over the winter. Now their time has come; pull on the gloves and get to work.
February is the perfect time to prune rose bushes. Pruning is a step that is required to maintain healthy roses. When roses are pruned, new growth is promoted by removing dead, broken or diseased canes. Pruning also allows the gardener to give their plant an attractive shape and encourage flowering, which is ultimately the reason roses are planted!
Belinda’s Dream rose before pruning. Image Credit Matthew Orwat
Deciding which roses to prune will depend on their class. Hybrid tea, grandiflora and floribunda roses are repeat bloomers and need a moderate to heavy annual pruning this time of year. Some old-fashioned roses and climbers that bloom only once a year should be treated differently and pruned immediately after flowering. They set their buds on old wood from the previous year’s growth; therefore, pruning them would remove most of this year’s blooms. An exception to this would be dead, diseased or damaged wood on any rose bush or canes that are crossing and rubbing. This should be removed immediately upon notice.
There are certain techniques that should be used when pruning any type of rose, no matter the time of year. Any pruning shear, saw or lopper you use should be sharp and sterile. Always wear protective gloves when dealing with roses, unless you don’t mind coming back bloody and mangled.
[warning]
Crown gall and canker can be spread between gardens and individual plants by dirty shears. To prevent the spread of disease, always disinfect pruning shears when beginning to prune with a 5-10% bleach or 20% rubbing alcohol solution, especiallly if they have been used in any other garden. If crown gall or canker has been found in one’s own garden, shears should be disinfected between each plant, no exception. This should also occur when bringing new plants into the garden, until they have been observed to be disease free.
[/warning]
The first step when pruning any rose is to remove dead, damaged or weak stems leaving only the most vigorous, healthy canes. Try to cut the stems one inch below darkened areas, making sure to cut back to green wood. Always make your cut at a 45-degree angle; this will keep water from sitting on top of a stem and causing rot. When pruning try to open up the center of the rose bush. Pruning like this will increase air circulation and help prevent diseases.
Pruning Cut on Belinda’s Dream rose. Image Credit Matthew Orwat
Since roses send out new growth from the bud just below a pruning cut, try to make pruning cuts above a leaf bud facing out from the center of the plant. Make your cut about ¼ inch above the bud and at the same angle as the bud. If any rubbing or crossing branches are noticed, the weakest of those branches should be removed.
Deadheading, or removing spent flowers, can also be done at this time of year. When deadheading, remove the flower by making a cut just above the next five or seven-leaf branch down on the stem. This will allow for a strong and healthy cane to grow in its place. If no live buds remain, remove the entire cane.
Modern reblooming roses (hybrid teas, floribundas, and grandifloras) should be pruned just as the buds begin to swell, which is around mid to late February. When practicing hard pruning, try to leave about four to eight large, healthy canes the diameter of your finger or larger on the shrub. For a more moderate approach, prune shrubs as discussed earlier and cut them back to about 12 to 24 inches from ground level. Generally, any cane thinner than a pencil should be removed.
Belinda’s Dream rose after pruning. Image Credit Matthew Orwat
Don’t worry about pruning recently purchased new roses. Newly purchased roses have most likely been pruned, and no further cutting is necessary. Hopefully with the help of this article you can make a date to spend some quality time with your roses this season. The price of neglect is overgrown roses that are not nearly as attractive.
First flush of properly pruned Belinda’s Dream shrub rose. Image credit Matthew Orwat
Article written by Taylor Vandiver with additional content about sanitation by Matthew Orwat
by Taylor Vandiver | Feb 25, 2014
So you have alkaline soil… What next?
Throughout the Panhandle, a common problem that often arises is finding a way to raise soil pH. This is due to the fact that we often encounter sandy, acid soils in this region. An often overlooked issue is explaining the process of gardening in a soil that tends to be more alkaline in nature.
Soil pH is measured using a scale from 0 to 14. On this scale, a value of 7 is neutral, pH values less than 7 are acidic, and pH values greater than 7 are alkaline. Soil pH directly affects the growth and quality of many landscape plants. Extreme pH levels can prevent certain nutrients from being available to plants. Therefore, a high pH may make it difficult to grow certain plants.
Often alkaline soils occur in the home landscape as a result of calcium carbonate-rich building materials (i.e., concrete, stucco, etc.) that may have been left in the soil following construction. Soils that contain limestone, marl or seashells are also usually alkaline in nature. There are a few measures that can be taken in order to combat high pH. Incorporating soil amendments containing organic material is the most common method implemented to reverse alkalinity. Peat or sphagnum peat moss is generally acidic and will lower pH better than other organic materials. Adding elemental sulfur is another common practice. A soil test will need to be performed often in order to add the correct amount of sulfur to reach an optimal pH level.
Lowering the pH of strongly alkaline soils is much more difficult than raising it. Unfortunately, there is no way to permanently lower the pH of soils severely impacted by alkaline construction materials. In these circumstances, it may be best to select plants that are tolerant of high pH conditions to avoid chronic plant nutrition problems.
Some plants that will tolerate alkaline soils:
-
Shrubs
- Glossy Abelia (Abelia Xgrandiflora)
- Sweet Shrub (Calycanthus floridus)
- Flowering Quince (Chaenomeles speciosa)
- Burford Holly (Ilex cornuta ‘Burfordii’)
- Indian Hawthorne (Rhaphiolepis indica)
Firebush is wonderful butterfly attractant. Photo courtesy of UF/IFAS.
-
Perennials
- Larkspur (Delphinium carolinianum)
- Pinks (Dianthus spp.)
- Firebush (Hamelia patens)
- Plumbago (Plumbago ariculata)
Zinnias come in a variety of colors, shapes and sizes. Photo courtesy of UF/IFAS.
-
Annuals
- California Poppy (Eschscholzia californica)
- Zinnias (Zinnia spp.)
- Cosmos (Cosmos bipinnatus)
by Julie McConnell | Feb 18, 2014
Lichen on trunk of oak tree. Image: Julie McConnell, UF/IFAS
Spanish moss and lichen have earned an inaccurate reputation for damaging trees and shrubs in the Florida landscape. Although they may be found in plants that are in decline or showing stress symptoms, they are simply taking advantage of space available to survive. Both plants are epiphytes and are obtaining moisture and nutrients from the atmosphere rather than from the plants they rest upon.
Spanish moss. Image: Julie McConnell, UF/IFAS
Lichen are more commonly found on plants that are in poor health because they need a plant that is growing slowly and access to sunlight. These conditions can typically be found in thin canopies of trees and shrubs under stress. Although they are firmly attached to the surface of the plant, they are not taking nutrients from the tree or shrub, but rather from the air and other sources such as organic debris and bird excrement. If you find lichen on your landscape plants, look further into what stress factors might be causing the plant to grow slowly such as compacted soil, extreme weather conditions, drought stress, disease or insect pressure.
Spanish moss does not harm trees and many people find it an appealing asset to their landscapes. Common misconceptions about Spanish moss include that the weight causes branches to break and that it is a host site for chiggers. Spanish moss is very light and any additional weight is typically insignificant. Although it may harbor some insects and provide nesting material for birds and other wildlife, Spanish moss in trees is not a site conducive to chiggers because they favor low-lying moist environments.
To read more about Spanish moss, lichens, and other common epiphytes please read the EDIS publication “Spanish Moss, Ball Moss, and Lichens – Harmless Epiphytes.”
![Figure 1 Note the black sooty mold coating the layers of white and grey scale, believed to be crapemyrtle bark scale, Eriococcus lagerstroemiae. [Photo by Gary Knox in Beijing, China]](https://nwdistrict.ifas.ufl.edu/hort/files/2014/03/crapemyrtle-scale.jpg)
![Figure 2. This white to grey colored scale oozes pink when crushed. [Photo by Gary Knox in Beijing, China]](https://nwdistrict.ifas.ufl.edu/hort/files/2014/03/crapemyrtlescale2.jpg)
![Figure 3. Dr. Gu is dismayed at seeing this crapemyrtle planting infested by scale (note the black sooty mold on stems). [Photo by Gary Knox in Beijing, China]](https://nwdistrict.ifas.ufl.edu/hort/files/2014/03/crapemyrtlescale3.jpg)
