by Matthew Orwat | Apr 8, 2014
Powdery mildew on rose bud. Image Credit Matthew Orwat.
Powdery mildew on rose leaf. Image Credit Matthew Orwat.
This spring powdery mildew has been prevalent on many non-resistant cultivars of ornamental plants, particularly rose and crapemyrtle.
Ideal conditions for powdery mildew development, warm days and cool nights followed by rain, have been present for several weeks in Northwest Florida.
This fungus, which looks like powdered sugar and is caused by several different species, appears on new growth and causes distorted and stunted leaf and flower development. It grows in thin layers on the surface of leaves and reproduces by spores.
Mild cases are of little concern, as most plants will grow out of it once environmental conditions change to be less favorable for development of the pathogen. Severe cases can cause distorted growth, leaf drop and flower destruction.
In these cases, fungicide application will protect new growth from this disease. Some lower toxicity fungicides that have been shown to have effectiveness on powdery mildew include neem oil and potassium bicarbonate (otherwise known as Baking Soda).
Sulfur can be used, but cannot be applied when temperatures reach above 90 ° F. Other chemical fungicides, including those containing myclobutanil, or azoxystrobin can be used but products obtained must be labeled for ornamental use. Remember, the label is the law.
Many disease resistant cultivars of rose and crapemyrtle exist, please follow the links provided for more information.
Powdery mildew on rose petiole. Image Credit Matthew Orwat.
Powdery mildew on rose. Image Credit Matthew Orwat.
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:
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Routine scouting and early identification. Submit samples for definitive confirmation.
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Destroy infected plants. There is no cure for rose rosette disease. Detection will prompt a quarantine by DPI until cleaned up.
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Eriophyid mite management in early spring is not necessary right now since it has not been found in Florida.
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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
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Active ingredient
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Fungicide group
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Trade name
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Copper hydroxide
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M1
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Hi-Yield ® Copper |
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Copper Sulfate
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M1
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Bonide® Copper Dust |
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Copper Octanoate
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M1
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Bonide® Liquid Copper, Natural Guard Copper Soap, Ortho® Disease B Gon® Copper Fungicide |
|
Sulfur
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M2
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Bonide® Sulfur Dust, Ferti-lome® Dusting Sulfur, Green Light, Hi-Yield® Dusting Wettable Sulphur, Ortho® Bug-B-Gon® Rose & Flower Care |
|
Mancozeb
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M3
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Bonide® Mancozeb |
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Captan
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M4
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Bonide® Captan 50WP, Hi-Yield® Captan 50W Fungicide |
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Chlorothalonil
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M5
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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
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3
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Spectracide Immunox® Multi-Purpose Fungicide |
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Propiconazole
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3
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Ferti-lome® Liquid Systemic Fungicide, Monterey Fungi-Fighter |
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Tebuconazole
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3
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Bayer Advanced™ Disease Control for Roses, Flowers & Shrubs |
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Tebuconazole + Imidacloprid
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3 +
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Bonide® Rose RX Systemic Drench, Feti-lome® 2-N-1 Systemic |
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Triforine
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3
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Ortho® RosePride® Disease Control |
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Calcium Polysulfide
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NC
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Hi-Yield® Lime Sulfur Spray |
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Neem Oil
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NC
|
Bonide® RX 3 in 1, Green Light® Neem Concentrate, Green Light® Rose Defense®, Monterey |
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Acetamiprid + Triticonazole
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NC + 3
|
Ortho® Bug B Gon® Insect & Disease Control |
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Acephate + Resmethrin + Triforine
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NC + NC + 3
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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.
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by Blake Thaxton | Nov 25, 2013
Citrus Canker lesions on leaves. Photo Credit: Beth Bolles, UF IFAS Extension – Escambia County
Authors: Blake Thaxton & Mary Derrick, UF/IFAS Extension – Santa Rosa Co. Mikaela Anderson, FDACS Division of Plant Inspection
Citrus canker is a serious disease of citrus trees that was recently confirmed for the first time in southern Santa Rosa County. Canker is caused by the bacterial pathogen Xanthomonas citri subsp. citri. Citrus canker has been a major pest of citrus in south and central Florida. It is economically damaging to the commercial industry and is also problematic to homeowners because it causes premature fruit drop, discolored fruit, and eventually causes the tree to become unproductive.
Canker was first introduced in 1912 into Florida and was declared eradicated in 1933. The disease was found again in the Tampa area on citrus in 1986. It was declared eradicated in 1994, but once again was found in 1995 in Miami. This time, the disease was not successfully eradicated in part because hurricanes made the disease too widespread to control. Despite its prevalence in south and central Florida, this disease has not been known in the Panhandle. The University of Florida and the Florida Department of Agriculture and Consumer Services’ Division of Plant Industry will be assessing the extent of the disease in Santa Rosa County in the coming months.
Lesions growing through the channels formed by the Citrus Leafminer insect. Photo Credit: Beth Bolles, UF IFAS Extension – Escambia County
How might you know if your citrus is infected by canker? One of the best indicators of canker is the presence of lesions, diseased spots, on the upper and lower surfaces of the leaves. The lesions will be raised and have a rough surface and will be surrounded by yellow halos. Similar lesions may be present on the fruit and stems as well.
[important]If you suspect that your citrus trees may have citrus canker please contact the Division of Plant Industry’s Helpline Center at 1-888-397-1517
before taking any action to reduce accidental spread of this disease. [/important]
Lesions formed on the stems. Photo Credit: Beth Bolles, UF IFAS Escambia County Extension
The disease is highly contagious to citrus only and spreads rapidly through wind, rain and via people on their hands, clothes, and tools. Do not transport any plant material that shows symptoms of canker. Decontamination practices should be used when going from one citrus tree to the next. Hand washing with soap and water for 20 seconds or more to eliminate bacterium on the skin should be practiced as well as using alcohol-based hand sanitizer. Pruning tools or other tools that come into contact with citrus should be disinfected by a fresh solution of 1 ounce of household bleach to 1 gallon of water. An old or dirty bleach solution is not able to disinfect because the chemical is no longer active.
[warning]Do Not Move a Plant Infected with Citrus Canker. Please Call your local Extension Office for further instructions[/warning]
For more information on citrus canker:
(The University of Florida IFAS Citrus Canker website provides a photo gallery of disease symptoms & information about the disease)
by Mary Salinas | Nov 4, 2013
For centuries, people annoyed with plant pests have used oils to control insects, mites, and even some fungal diseases. Current oil products are better than ever!
Sample oil products for pest control. Photo by Mary Derrick.
Commercially available horticultural oils are mineral oils from refined petroleum products. Impurities are removed and then an emulsifying agent is added that allows the oil to mix with water for application. Neem oil is a newer product that has become increasingly popular; the oil is an extract of the seeds of the neem tree.
What are some of the advantages of using an oil for pest control?
- Oils are inexpensive and easy to apply
- Oils can be used on most plants (check the label for a list!)
- Oils control a wide range of pests that feed on plants (again, check the label for a list of pests the product will control!)
- Oils pose a low risk to people, pets, and desirable beneficial predators
- Since oils kill pests by blocking their breathing holes (spiracles) and/or gumming up their mouthparts, there is no chance for resistance to develop
- One product can control both insects and some diseases like powdery mildew at once
- Oils can be combined with some other pesticides to provide greater control
[warning] Don’t combine with, or use within 30 days of, any sulfur based pesticide. The combination can harm your plants![/warning]
There are always drawbacks to a product. What are the drawbacks?
- Some plants (including cryptomeria, junipers, cedars, maples, and redbud) are damaged by oils – check the label!
- Ensure good coverage during spraying as pests must be contacted with the oil in order for the control to work
- Oils break down quickly and reapplication may be necessary
- Check the label for instructions on the temperature range when it can be used. Older formulations generally are safe when temperatures are in the 40 to 80°F range but ultra-fine oils can generally be safely applied during hotter weather.
For further information:
Natural Products for Insect Pest Management from UF IFAS Extension
Insect Control: Horticultural Oils from Colorado State University Extension
Less Toxic Pesticides from Clemson University Cooperative Extension
by Beth Bolles | Oct 7, 2013
It is now too late for homeowners to apply nitrogen fertilzers to warm season lawns for the year.
Many fertilizers are available in the stores and promotions are everywhere that state that now is the time for lawns to be winterized. Applications of nitrogen after mid September can lead to turf problems next spring. Nitrogen encourages growth of the grass which uses up stored food. As the weather frequently changes throughout the winter months, grasses may use up their food reserves and not have enough carbohydrates to regrow when weather consistently warms next year.
Besides creating unnessary new growth as grasses enter winter dormancy, lawns receive additional stresses when gardeners add nitrogen this late in the season One such issue with a late season application of nitrogen is that it can make the grass more susceptible to large patch fungus. This fungus is active when soil temperatures range between 75 and 65 degrees F. Nitrogen applications encourage lush growth which can increase the incidence of the disease.
Large patch fungus can be more of a problem on turf following late season nitrogen applications.
For those that feel it necessary to apply some type of fertilizer now, potassium may be applied for the next couple of weeks. Potassium is often sold as a 0-0-60 and the rate is about 1.5 lbs. of the fertilizer per 1,000 square feet of lawn.
Learn much more about lawn fertilization from the University of Florida IFAS Extension.
