A couple weeks ago, I was on a site visit to check out some issues on Canary Island Date Palms. The account manager on the property requested a site visit because he thought the palms were infested with scale insects. He noticed the issue on a number of the properties he manages and he was concerned it was an epidemic. From a distance, lower fronds were yellowing from the outside in and the tips were necrotic. These are signs of potassium deficiency with possible magnesium deficiency mixed in.
Transitional leaf showing potassium deficiency (tip) and magnesium deficiency (base) symptoms. Photo Credit: T.K. Broschat, University of Florida/IFAS Extension
Nutrient deficiencies are slow to correct in palm trees. It’s much easier to prevent deficiencies from occurring by using a palm fertilizer that has the analysis 8N-2P2O5-12K2O+4Mg with micronutrients. Even if the palms are part of a landscape which includes turf and other plants that require additional nitrogen, it is best to use a palm fertilizer with the analysis previously listed over a radius at least 25 feet out from the palms. However, poor nutrition wasn’t the only problem with these palms.
Upon closer look, the leaflets were speckled with little bumps. Each bump had a little white tail. These are the fruiting structures of graphiola leaf spot also known as false smut.
Graphiola leaf spot (false smut) on a Canary Island Date Palm. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
Graphiola leaf spot is a fungal leaf disease caused by Graphiola phoenicis. Canary Island Date Palms are especially susceptible to this disease. Graphiola leaf spot is primarily an aesthetic issue and doesn’t cause much harm to the palms infected. In fact, the nutrient deficiencies observed in these palms are much more detrimental to their health.
Graphiola leaf spot affects the lower fronds first. If the diseased, lower fronds are not showing signs of nutrient deficiencies then they can be pruned off and removed from the site. All naturally fallen fronds should be removed from the site to reduce the likelihood of fungal spores being splashed onto the healthy, living fronds. A fungicide containing copper can be applied to help prevent the spread of the disease, but it will not cure the infected fronds. Palms can be a beautiful addition to the landscape and most diseases and abiotic disorders can be managed and prevented with proper pruning, correct fertilizer rates, and precise irrigation.
(UF/IFAS photo Thomas Wright)
Northwest Florida’s weather patterns can present challenges to maintaining a health lawn. Heavy rains promote fast growth and relentless sunshine causes lawns to fade. In the last 200 days we have received at least 68 days of rain. While the rest of Florida was experiencing record drought, the Panhandle was experiencing torrential downpours. With every drop of rain your spring fertilizer is being metabolized by the lawn, reducing how many nutrients remain in the soil. Even the best slow-release fertilizer will only last 3-4 months. The message is: “It’s time for more fertilizer.”
A healthy lawn is an important component of the urban landscape. Not only do lawns increase the value of a property, they also reduce soil erosion, filter stormwater runoff, cool the air, and reduce glare and noise. A healthy lawn effectively filters and traps sediment and pollutants that could otherwise contaminate surface waters and groundwater. Lawns require nutrients throughout the growing season to stay healthy. In Northwest Florida the growing season is typically April to October.
Proper fertilization consists of selecting the right type of fertilizer and applying it at the right time and in the right amount for maximum plant uptake. The type of fertilizer should be based on a soil test, available through UF/IFAS Extension. The timing of application and amount of fertilizer is dependent on the research-based recommendations for the grass species and the fertilizer analysis of the product being used.
Chart excerpted from Florida Friendly Landscaping publication
Select only a fertilizer that states that the product is for use on residential turf. Do not use a fertilizer meant for flower or vegetable gardens on lawns. By Florida Administrative Code, Rule 5E-1.003, the Urban Turf Rule requires that the fertilizers being applied to residential lawns are labeled for the site and the application rates be followed. Typically, these products will contain both slow-release nitrogen and low or no phosphorus. Slow-release nitrogen will provide a longer-lasting response from the grass and reduces the potential for burning. For more information on the Urban Turf Rule go to: http://www.edis.ifas.ufl.edu/pdffiles/EP/EP35300.pdf.
With frequent rain the soil is also losing iron. Keep in mind that the green fading to yellow appearance in your lawn may be an iron deficiency. Before applying your summer fertilizer put out a liquid chelated iron. It will improve the health of the lawn while you are trying to find a dry day to fertilize. While it is necessary to water in fertilizer with ¼” of water to reduce burn potential and volatilization, never apply fertilizer when heavy rain is expected. The rainfall over ¼” can encourage runoff and/or leaching of that fertilizer, which can be costly and environmentally harmful.
It is common in Northwest Florida for palms to show signs of nutrient deficiencies. In general our sandy soil is often nutrient poor and available nutrients can easily move out of soils with frequent rainfall. In landscapes where fertilization is occurring, often the wrong types of fertilizer are applied. Fertilizer miss-application actually increases nutrient problems for the palm.
Palms can be deficient in many nutrients but the most common deficiencies we see in landscapes are from inadequate amounts potassium and magnesium. The simple solution would be to purchase a fertilizer labeled for palms to correct the problem. The difficulty is that most easily available fertilizers for palms do not have the correct form of nutrients that are required for the problems. With the exception of nitrogen, all other nutrients are in a quick release form so while the slow release nitrogen lasts for 2-3 months, all other nutrients have been used up. In response, the palm is encouraged to grow by the nitrogen but does not have enough of the other critical nutrients to carry out vital plant functions. What we see is often older leaves that are yellowing, browning, and die off before they should because the plant is pulling any available potassium and magnesium from old fronds to support new growth. Without the application of proper nutrients to the soil, the deficiency can continue until even new fronds are affected or the palm dies.
The fertilizer used for lawns does not have all the slow release and correct forms of nutrients for the palms. Older leaves turn yellow and brown indicating potassium deficiency. Photo by Beth Bolles, UF IFAS Extension Escambia County.
There is a solution that will help keep your palms healthy and attractive. Make sure you choose a specially designed fertilizer that has all nutrients in slow release form. Look for an analysis such as 8-2-12-4 (Nitrogen-Phosphorus-Potassium-Magnesium). Also read further on the label for Polymer Coated Sulfate of Potash, Magnesium Sulfate (Kieserite), and Chelate (Iron EDTA). These are the forms of nutrients that will be beneficial to your palms.
Look in the area ‘Derived From’ (outlined in blue) on your fertilizer label to find the forms of nutrients. Photo by Dr. Monica Elliott, US/IFAS Extension.
If you have a mixed landscape where the palms are planted in the lawn, be sure to keep all lawn fertilizers out of the root zone of the palms. Lawn fertilizers do not have the correct forms of nutrients for palms. Remember also that palms roots extend many feet beyond the palm canopy so your ‘no lawn fertilizer zone’ may be past the mulch ring.
The recommendation from the University of Florida is 1.5 pounds of fertilizer over a 100 square foot area. Broadcast this on top of the ground and lightly water after application. In North Florida, you will likely apply the correct palm fertilizer about at least two times in May and end of August or 1st of September. If you are not able to use a palm fertilizer with the correct form of slow release nutrients, it is best not to fertilize palms at all.
Dooryard citrus enthusiasts may be uncertain about late winter management of Satsuma and other citrus trees. Several questions that have come in to the Extension Office recently include:
- Should I prune my trees?
- Why are the leaves yellow?
- How soon should I fertilize?
The focus of this article is to provide some answers to these common questions.
Should I prune my trees?
This is a complicated question that is best answered with “it depends…” Pruning is not necessary for citrus, as it is in many temperate fruits, to have excellent production quality and quantity. Citrus trees perform excellently with minimal pruning. The only pruning necessary for most citrus is removing crossing or rubbing branches while shaping young trees, removing dead wood, and pruning out suckers from the root-stock. Homeowners may choose to prune citrus trees to keep them small, but this will reduce potential yield, since bigger trees produce more fruit.
Often, maturing Satsuma trees produce long vertical branches. It is tempting to prune these off, since they make the tree look unbalanced. To maximize yield, allow these branches to weep with the heavy load of fruit until they touch the ground. This allows increased surface area for the tree, since the low areas around the trunk are not bare. Additionally, weeds are suppressed since the low branches shade out weed growth. The ground under the trees remains bare, thus allowing heat from the soil to radiate up during cold weather events. The extra branches around the trunk offer added protection to the bud union as well. If smaller trees are desired for ease of harvest, ‘flying dragon’ root-stock offers dwarfing benefits, so that the mature scion cultivar size will only grow to 8-10 feet tall.
Heavy fruit loads were produced in many home gardens throughout Northwest Florida last year. When fruiting is heavy, citrus trees translocate nitrogen and other nutrients from older leaves to newer growth and fruit. Therefore, temporary yellowing may occur and last until trees resume growing in the spring. Remember, never fertilize after early September, since fertilizing this late in the year can reduce fruit quality and increase potential for cold injury. If a deficiency, as in the photo above persists through spring, consider a soil test, or consult a citrus production publication to determine if additional fertilizer should be added to your fertilizer program.
How soon should you fertilize?
Although most Florida citrus publications recommend fertilizing citrus in February, they don’t take into account the potential for late frost in the Panhandle. Thus it makes more sense to wait until mid-March for the first fertilizer application in this region. Citrus trees don’t require a fertilizer with a high percentage of nitrogen, so it is best for fruit quality if an analysis of around 8-8-8 with micro-nutrients is used. Fertilizer should be applied in the drip-line of the tree, not around the trunk. The drip-line of a mature tree is generally considered to extend one foot from the trunk out to one foot from the edge of the furthest branch tip from the trunk. For fertilizer quantity recommendation see the chart below.
Through awareness of the unique managements techniques inherent to dooryard citrus production in the Panhandle, home gardeners are offered an opportunity to provide their friends and family with a substantial portion of their annual citrus !
For more information on this topic please use the following link to the UF/IFAS Publication:
When you don’t know what’s ailing your plant, ask an expert.
Many gardeners get stumped when a favorite plant of theirs comes down with a strange “something”. Many of these gardeners know about UF/IFAS Extension and call their local horticulture and agriculture agents for assistance in figuring out what’s going on. However, even these experts are often stumped by what they see. Fortunately, the agents have another layer of experts to fall back on. In addition to the resources in Gainesville, we have the Plant Disease Diagnostic Clinic, located at the North Florida Research Center in Quincy. Plant pathologists here can help determine what fungus, bacteria, virus, or viroid may be the problem.
Plant pathologists are basically plant doctors. They use all sorts of sophisticated techniques to determine what is the cause of a particular plant problem, from growing out fungal spores to examining DNA. Not only do these plant doctors tell us what the ailment is, they also provide recommended cures, or control options. They are also doing research to prevent different diseases from taking hold in our area and reduce the impact on our local growers.
Plant pathologist at work!
At a recent workshop in Quincy, we learned that plant pathology researchers are working on a fungus that affects watermelons, virus and bacteria that can wipe out a farmer’s tomato crop, and a virus that could impact our local roses. Working as a team of scientists, they study these pathogens in the lab and conduct controlled field experiments to figure out which techniques are most effective. Some of this research is leading to different methods and/or products that can help growers and gardeners alike keep their fields and landscapes healthy.
So, if your plants have problems, please contact your local Extension Office. If they don’t know the answer, then the network of scientists, including plant pathologists, in the UF/IFAS Extension family can be called on for backup to provide you with the best possible answer.
Information on gardening practices is freely shared between gardeners and many times the good advice is helpful in plant selection and improving plant growth. There are some passed along practices that are not always suitable for every situation and gardeners may need to investigate a little deeper before implementing the good advice.
Soil test kit available form your local Extension office. Photo: Mary Derrick, UF/IFAS.
One common recommendation from gardeners is to apply Epsom salts to the soil to improve plant growth. Gardeners may have used Epsom salts for various plants in the garden and viewed plants that appear to grow better or have improved leaf color. Therefore a general recommendation to help others who have some general plant problems or off color leaves is to apply Epsom salts.
Before you apply Epsom salts to your garden, understand that it is an inorganic fertilizer, specifically magnesium sulfate. Plants make their own food but they derive most of their nutrients needed for important functions form the soil. Magnesium is one of the nutrients that is essential in photosynthesis. At times, our sandy soils may be lacking in nutrients but there may be plenty of nutrients available for plants.
The recommendation to apply Epsom salts may sound like a good idea but gardeners should always make sure that magnesium is needed before any applications. Too much magnesium in the soil can interfere with the uptake of other nutrients by plants. You could create more of a problem by indiscriminately applying Epsom salts when magnesium is not needed.
As you hear often from the University of Florida Extension, conduct a soil test before applying fertilizer to determine the major nutrient levels available in your soil. This $7.00 test will help you better manage plant nutrition. If you need assistance interpreting soil test results, contact your local county Extension office.