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.
by Matthew Orwat | Aug 19, 2013
Cercospora in Pepper
Image Credit Matthew Orwat
This summer’s rainy and humid weather has created a perfect environment for the proliferation of a variety of fungal diseases. In particular, Cercospora is a genus of fungus of which there are over 1,200 different species. Because there are so many species of this fungus, many different plant species are affected including many garden vegetables and ornamentals.
Cercospora leaf spot in Pepper
Image Credit Matthew Orwat
Cercospora causes purple, brown or black spots on a variety of garden vegetables and ornamental shrubs. The spots usually include a grey dead area in the center and a yellow “halo” or “ring” surrounding the entire spot. This disease usually starts at the base and interior of the plant, where there is more moisture and less air circulation, and moves outward.
Severe Cercospora infections have the ability to defoliate entire plants within a season and kill garden annuals, such as pepper, within a season. On shrubs, turf and perennials, Cercospora ranges from minor annoyance to major disease depending on the resistance of the cultivar or species. Serious infections can kill some ornamentals, such as Indian Hawthorn or Rose, in three years.
Several methods exist to limit the spread and severity of Cercospora outbreaks. It is a good practice to remove all dead plants and leaf litter from the garden. If Cercosproa infection occurs, remove and dispose of dead plants and pick up all leaf litter from the garden immediately upon drop. This will limit the fungal spore’s ability to reproduce. Another preventative strategy is to reduce water splash on leaves. Splashing water spreads Cercospora spores and allows them to take hold on a leaf. Irrigate the vegetable garden or landscape with drip irrigation to avoid wet leaves. Additionally, irrigate in the morning, so plants will not remain wet overnight. Cercospora requires 16 hours of moisture to reproduce. Specifically, infection of Indian Hawthorn has proven to be reduced by switching from overhead to drip irrigation.
Cercospora Infection on Rose
Image Credit U-Scout (Mathews Paret)
If fungicides must be used, be sure to follow label directions since some products labeled for the home ornamental garden, such as Chlorothalonil, are not labeled for turf. Be sure to use fungicides with more than one mode of action, since resistance may develop if only one type of fungicide is used.
For more information, please consult the following UF / IFAS publications regarding Cercospora:
Also, contact your County Extension Office for additional assistance.
by Larry Williams | Jul 22, 2013
Gray Leaf Spot is a common fungal disease of St. Augustinegrass. Recent wet conditions have promoted this disease. This includes high humidity, heavy dews and particularly frequent afternoon and evening rains.
Gray leaf spot symptoms on St. Augustinegrass. Photo credit: UF/IFAS Extension
The individual spots or lesions are first seen as tiny brownish spots smaller than a pinhead. As they become larger, they will be circular and then begin to elongate lengthwise along the leaf. The spots will become brown to grayish in appearance. Numerous spots or lesions may be found on an individual leaf. Heavily infected leaves begin to turn brown and wither, usually beginning at the tip of the blade.
Gray leaf spot can move rapidly during prolonged warm, wet periods. Over watering or irrigating in the evening provides the prolonged period of wetness required for disease infection. For more information on how to correctly water a Florida lawn, visit the UF / IFAS Lawn Watering Website.
According to the Florida Lawn Handbook, “Severity of the disease is enhanced by application of readily available nitrogen fertilizer and is proportional to the amount of nitrogen applied.” Select fertilizers that are low in nitrogen or that have slow release nitrogen. Be careful to not overdo it in fertilizing your lawn and do not apply a high nitrogen fertilizer on top of an already infected lawn. Also, some lawn weed killers such as atrazine will increase the susceptibility of the grass to gray leaf spot.
Irrigate during early morning hours to minimize the period in which the grass is wet and water only on an as needed basis, watering less often but deeply. Avoid frequent, shallow watering and don’t irrigate when the lawn is already wet from rain. With the recent frequent rains, very little to no supplemental irrigation has been needed on most lawns in our area. Avoid leaving irrigation timers on when adequate rainfall has occurred. It’s best to operate irrigation controllers on manual so that the lawn can be monitored and irrigation provided during dry times.
If the disease outbreak is severe, fungicide may be needed. Look for products containing propiconazole, triadimefon or thiophanate-methyl. Always follow the product’s label directions and precautions.
For more information on maintaining a Florida lawn, contact your County UF/IFAS Extension Office or visit the YourFloridaLawn Website.
by Julie McConnell | Jul 22, 2013
When you contact your local extension office for pest control recommendations you will likely hear “follow the label” over and over again. So, why do we emphasize the pesticide label so strongly when talking to both homeowners and landscape professionals?
There are many important reasons why you should always read and follow label instructions.
- The Label is the Law – using a pesticide in a manner that is inconsistent with the label is a violation of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Using a product inconsistent with the label includes, but is not limited to: rate of application, use on site not labeled for control, use on plants/lawns not labeled, frequency of application, method of application, distance from water sources, etc.
- Safety of Humans – using a product incorrectly can cause harm or even lead to death
- Safety to Non-target Organisms – this includes non-target insects, reptiles, birds, fish, mammals, and plants which can lead to negative impact on environment and economy
- Effectiveness of Product – millions of dollars are spent to figure out the most effective way a product works best, follow their instructions! (remember the manufacturer wants the product to be effective so that you’ll recommend to others and buy it again)
- Increased Resistance Decreases Control – improper application and a failure to rotate products as part of an integrated pest management program can increase likelihood of resistant pest populations
Before shopping for any pesticides, do some research:
- Has the pest been identified properly? What life cycle stage is the pest at? Most pesticides have different levels of efficacy depending on life cycle of target. For example, glyphosate works best on young plants that have not yet flowered. Your local extension office can help with identification and timing of control methods
- Can you control the pest with cultural practices such dethatching, irrigation, fertilizer, or mowing height changes? Start with the least toxic method of control and only work up if ineffective
- Read the label before you buy to be sure that it is labeled for your plant /lawn, target pest. The label will also tell you what equipment you’ll need to mix and apply and safety equipment. If product is not ready to use, be sure you can follow mixing and application procedures safely
- Are there particular environmental precautionary statements that are relevant to your site?
- How much do you need? Have you measured the area for treatment? Just as you don’t want to make multiple trips to the store, you also do not want a lot of excess chemicals on hand. They have to be stored or disposed of according to label instructions, too
For more information about pesticide labels read EDIS PI-34 Interpreting Pesticide Label Wording.
