Palm Tree Problems

Palm Tree Problems

Palm trees are great for adding a tropical feel to your landscape.  For the most part, they are easy to care for, however there are a number of environmental and nutritional factors that can affect palm tree growth.  Extended drought conditions can cause palm trunk to contract or shrivel and extended periods of moisture can cause trunks to swell and crack.

A palm tree with an irregularly shaped trunk due to water stress.

A palm tree with an irregularly shaped trunk due to water stress. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County

Palm trees are monocots and do not have lateral meristems or vascular cambium.  In dicot and coniferous trees these structures produce additional xylem (water transport structures) internally and phloem (nutrient transport structures) and bark externally.  This means that once the apical meristem (frond producing portion of the palm) dies, the tree dies.  It also means that wounds to the trunks of palms are visible for life instead of healing over like in dicots.  If you were to cut the top out of a red maple, a number of it’s branches would fight to take over as the main trunk.  If you were to cut the top out of a palm tree , you would be left with a dead snag for a tree.  Palms certainly have unique structures and growing habits.  Visit this publication from Dr. Timothy Broschat for more information on palm tree anatomy and morphology.

A palm tree with a wound near the base of its trunk.

A palm tree with a wound near the base of its trunk. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County

Palm trees display nutritional disorders differently from other trees.  Their nutritional balance gets disrupted if too much nitrogen is applied.  This often happens when high nitrogen turfgrass fertilizers are applied near palm plantings.  The recommended palm fertilizer is 8-2-12 (nitrogen-phosphorus-potassium) plus 4 magnesium all available in 100% slow release form.  A soil test is recommended to determine if other micronutrients are needed in addition to magnesium.

Potassium-deficient older leaf of Dictyosperma album (hurricane palm) showing translucent yellow-orange spotting.

Potassium-deficient older leaf of Dictyosperma album (hurricane palm) showing translucent yellow-orange spotting. Photo Credit: Timothy K. Broschat, University of Florida/IFAS

Potassium is one of the most common nutrient deficiencies observed in palm trees.  For more detailed information on palm tree nutrient deficiencies please visit the publication: Nutrient Deficiencies of Landscape and Field-Grown Palms in Florida.

This article provides just a glimpse of some of the common issues that affect palms.  For more information on what could be going on with your palm trees and general palm tree care please visit Ask IFAS: Palm Care.

Saw palmetto

Saw palmetto

Saw palmettos provide crucial ecosystem services for the forests of Florida. Photo credit: Carrie Stevenson, UF IFAS Extension

The saw palmetto (Serenoa repens) is a classic symbol of Florida. Found in upland habitats and just to the edge of wetlands, their brilliant green fronds stand out in the mostly brown pine flatwoods and oak hammocks to which they are endemic. The shrublike saw palmetto thrives in sandy soils, is highly salt tolerant, and is tough as nails. The plant’s root is one of the sturdiest in nature. Imagine the trunk of a palm tree laid horizontally and just underground—this is the plant’s base. This root system lends stability and tolerance to nearly every tough Florida growing condition, including drought, floods, and fire. Saw palmettos are extremely slow growing, and there are stands in south Florida in which botanists have found individual plants and clonal colonies several thousand years old. Saw palmettos are one of the few members of the palm family that thrive in the panhandle. While many palm trees are planted here, most are native to more southern climates with warmer winters and karst geology—a higher pH soil composed of limestone and often prone to springs and sinkholes.

The tough, serrated edges of the saw palmetto gave it its name. Photo credit: Carrie Stevenson, UF IFAS Extension

The saw palmetto’s name comes from the serrated, saw-like edges of the stem. These are quite tough and can cut your skin and clothing if not careful. A very similar palmetto, the bluestem, grows in wetter soils. It can be differentiated from the saw palmetto because its stems are smooth—no serrated edges—and the whole plant has a bluish cast to it.

The saw palmetto has long been prized by humans for its practical uses. The “ethnobotanical” history of this plant has ties to Native American tribes who used the fronds for roofing and building material, brooms, fishing nets, and fans. The leaves were utilized for rope, and multiple plant parts for food and medicine. The dark blue/black fruit of the saw palmetto was considered an aphrodisiac and has been used to treat prostate problems for centuries. According to a UF publication on the saw palmetto, “Modern day development of a purified extract from the berries greatly improves symptoms of enlarged prostate. Florida is the biggest source and producer of saw palmetto products. With about 2,000 tons harvested from South Florida and exported to Europe each year, the fruit crop estimate is $50 million a year in the state.”

Saw palmetto berries are a staple of Florida wildlife diets. Photo credit: UF School of Forest Resources & Conservation

Besides the human uses, saw palmetto serves as a crucial component in the diet of native wildlife. Florida black bears, panthers, 20 other species of mammals, over 100 types of birds, 25 amphibians, over 60 reptiles, and countless insects depend on saw palmetto berries as part of their diet. The wild harvest of saw palmettos is regulated by the state to prevent overharvesting and negative impacts to the wildlife food supply.

Saw palmettos also make a great home landscape plant, as they can grow in a wide variety of conditions, provide wildlife food and habitat, and add visual interest. There are few plants more “low-maintenance” than an established saw palmetto. A mature one is so difficult to remove, that it’s best to leave it where it is anyway!

Upgrade Your Gardening with Quality Pruners!

Upgrade Your Gardening with Quality Pruners!

There is an old saying that rings true in pretty much any situation – “You get what you pay for.”  Gardening tools, especially pruners, are no exception.  We’ve all been there, fumbling around with a pair of rusty, dull, cheap garden pruners that just barely get the job done.  Unfortunately, they can also do considerable harm to the plants you’re trying to improve, as anything short of a nice, sharp, clean cut introduces the potential for insect/disease infestation and will produce a wound that takes much longer to heal, if it ever heals properly at all.  You wouldn’t want your doctor to start hacking away at you with a dirty, second-rate scalpel.  Don’t subject your plants to the same treatment!  While I’m not advocating blowing hundreds or thousands of dollars outfitting your garden tool shed with top of the line everything, investing in a pair of quality bypass hand pruners will pay dividends many years into the future and make your gardening experience much more enjoyable!

The classic Felco #4 bypass hand pruners. Photo courtesy of Walton County Master Gardener Andrea Schnapp.

Found in three designs, from old-fashioned anvil pruners that smush and smash their way to a cut, to ratcheting pruners that make short work of larger branches but tend to be cumbersome and complicated, to bypass pruners that produce clean cuts in a scissor-like manner, hand pruners accomplish many tasks in the landscape.  From cutting small limbs, to harvesting vegetables, to deadheading annual flowers and everything in between, there isn’t a more frequently used, versatile tool.  Therefore, it makes sense to buy a quality pair that will perform excellently, still be snipping long after your pruning days are over (if you take care of them), and that are comfortable enough you will enjoy using them.  When shopping for your pair of “forever” pruners, there are a few things to look for.

  • Only use bypass style pruners. Your plants will appreciate it.
  • Look for heavy duty pruners with frames made from quality aluminum or stainless steel; they won’t rust and won’t easily bend or break.
  • Buy pruners with replaceable parts. This is especially key because springs eventually rust and gum up and blades break and will eventually lose their ability to hold an edge over time (though you can and should resharpen them).

There are two commonly found brands that fit all three above criteria, albeit at different price points.  For a high quality “budget” blade, various models from Corona do an excellent job for the money ($20-30) and won’t hurt your feelings too badly if you happen to lose a pair.  Should you decide to splurge a little, Felco makes sharp, indestructible pruners, in multiple models around $50 to fit all size hands.  Felco has become the horticulture industry standard and you’d be hard pressed to find a nursery owner or landscaper that didn’t own a pair (or two).

Corona ComfortGel bypass hand pruner. Photo courtesy of Daniel Leonard.

Regardless of which brand you buy (and there are many more than the two above listed) a pair of well-made pruners, if taken care of, should last a lifetime and make your gardening experience much more enjoyable for you and your plants!  If you have any questions about gardening tools or equipment or any other horticulture or agronomic topic, feel free to contact your local UF/IFAS Extension Office.  Happy Gardening!

 

Yellow is Not a Normal Sago Color

Yellow is Not a Normal Sago Color

Photo by: Sheila Dunning

The first sign that something is going wrong in a plant is often a loss of the color green.  When a sago is forming all new yellow leaves it is a matter of concern.  Typically, this a common nutritional deficiency – manganese.  Sandy soils of the Panhandle have a hard time retaining nutrients.  Manganese and other micronutrient availability is highly influenced by soil pH.  Being an essential plant nutrient, manganese is critical to growth.  More specifically, it is the base of the metalloenzyme cluster of the oxygen evolving complex (OEC) in photosystem II (PSII).  I hope that means more to you than it does me.  Basically, manganese is part of the photosynthetic activity and since it isn’t very mobile in the plant, the new growth of sagos turns yellow.

If the nutrient deficiency isn’t corrected, the newly-formed leaves will become deformed and turn brown.  In a sago this is referred to as “frizzle-top”.  Many people believe the plant has a disease when they see the symptoms and may apply fungicides to no avail.  Keep in mind the discoloration of the affected leaves cannot be reversed.  However, manganese replacement in the soil will enable the sago to form normal leaves with the next growth phase. Damaged fronds can be removed later to improve the appearance of the sago over time.

Begin this process by determining the soil pH through a soil test.  Your local Extension office can help you obtain lab submission forms and explain the collection procedure.  Manganese is most available for uptake by sagos when the soil pH is between 5.5 and 6.5.  If the pH is above 6.5, larger amounts of manganese will have to be present before the plant can utilize it.  When the soil pH is below 5.5 the nutrient is quickly leached out of the soil during rain events.

To correct a manganese deficiency the sago plant will need to receive manganese sulfate.  The product is readily available at local nurseries, garden centers and building supply stores. The amount needed for each plant will vary with the size of the sago and the existing soil pH.  Sagos growing in sandy, acidic soil will require less manganese sulfate than those in high pH soils.  Refer to the package label for application rates.

Time To Control Winter Scales

Time To Control Winter Scales

Scale insects on a cabbage palm.

Scale insects on a cabbage palm (Sabal palmetto). Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County

This week I was on a couple site visits to look on some cabbage palms (Sabal palmetto) and some banana shrubs (Michelia figo).  The palms had a white, waxy substance on their frond petioles and the banana shrubs had white specs on the tops of their leaves.  Upon further investigation, I realized the waxy substance and specs were both different species of scales.  Scale insects are serious pests of a number of ornamental plants.  Here in Florida there are 13 different families of scales with the most common being armored scales, soft scales, and mealybugs.  Scales have piercing-sucking mouthparts which they use to siphon fluids from the leaves, stems, and sometimes roots of many ornamental plants.  Heavy infestations cause extensive leaf yellowing, premature leaf drop, branch dieback, and eventually plant death.

Scale Biology

The life cycle of a scale begins with eggs being laid beneath wax coverings or beneath the adult female.  Eggs typically hatch in 1 to 3 weeks.  The newly hatched nymphs, called crawlers, move around a plant until they find a spot to feed.  Once a feeding site is located, their piercing sucking mouthparts are inserted into the plant and the crawlers begin to feed and grow.  The males of many scale species develop wings as adults and fly to other plants to reproduce.

magnolia white scales

Magnolia white scales on a banana shrub (Michelia figo). Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County

Armored Scales

Armored scales get their armor by secreting a waxy covering over their bodies that is not attached.  The scale lives under this covering and uses it as a protection to feed under.  Armored scales can be almost any color or shape and range anywhere from 1/16 to 1/8 inch in diameter.  For females, these shapes range from circular to oval to long and slender.  The males typically have coverings that are more elongate and smaller than the females.  As adults, the males are tiny, winged, gnat-like insects and are rarely seen.

Gloomy scale, Melanaspis tenebricosa, with armored covering removed.

Gloomy scale (Melanaspis tenebricosa) with armored covering removed. Photo Credit: A. G. Dale, University of Florida/IFAS

Soft Scales

Similar to armored scales, soft scales secrete a waxy covering, but it is attached to their bodies.  Soft scales can be a number of colors, shapes, and sizes and range anywhere from 1/8 to 1/2 inch in diameter.  Their shapes vary from spherical to nearly flat.

Population of adult and immature tuttle mealybugs (Brevennia rehi) on a blade of zoysiagrass.

Population of adult and immature tuttle mealybugs (Brevennia rehi) on a blade of zoysiagrass. Photo Credit: Lyle J. Buss, University of Florida/IFAS

Mealybugs

Mealybugs are soft-bodied insects that possess a covering of flocculent, white, waxy filaments.  They are about 1/8 inch in length and usually pinkish or yellowish in color.  Mealybugs have piercing-sucking mouthparts which they use to siphon fluids from the leaves, stems, and sometimes roots of many ornamental plants.  Mealybug damage produces discolored, wilted, and deformed leaves.

Scale and Mealybug Management

  • Cultural Control – Plant inspection prior to purchase or installation is the first line of defense against a scale or mealybug population.  Make sure to inspect the undersides of leaves and plant stems.  Infested sections of plants can be pruned and plant material should be cleaned from the planting area and discarded.  Also, you can increase air flow and decrease humidity by proper installation and pruning.  Over-fertilizing can also increase pest populations.

Larva of a brown lacewing (Neuroptera: Hemerobiidae) preparing to attack and feed on an aphid. The black-colored aphid to the right was probably parasitized by a wasp. Photograph by Lyle J. Buss, University of Florida.

Larva of a brown lacewing. Credits: Lyle Buss, University of Florida.

  • Biological Control – Predators, such as ladybugs and green lacewings, are usually present in large enough numbers to suppress scales and mealybugs to a desirable threshold.  However, broad-spectrum insecticides and bad weather can reduce predator numbers.  Look for signs of predation by inspecting dead scales for jagged holes in their waxy coatings.  If predation signs are present, use more selective chemical controls and oils as opposed to broad-spectrum products.
  • Chemical Control – Timing is everything when it comes to managing scale and mealybug insects.  Crawler activity is more pronounced with the flush of new plant growth in the spring.  Before application, prune infested plant parts off first to promote greater penetration of insecticides into the foliage.  Dormant Oils are often used in the winter to smother scale insects. These are good choices to implement because they don’t harm non-target or beneficial insects. Care must be taken to read the label and use them at the correct temperature, since use in hot weather may burn foliage. Contact products (acephate, bifenthrin, carbaryl, etc.) must be applied to inhibit the crawler stages of these insects and systemic products (acetamiprid, imidacloprid, thiamethoxam, etc.) can be used on the sessile growth stage.  Plants should be sprayed thoroughly to the point of drip or “run off” from leaves, twigs, and stems.  Repeated applications may still be necessary even if the timing is right, as crawler populations are often large and crawlers like to hide under old waxy scales.  Systemic drenches are also a viable option.  With good spray coverage, horticultural oils can kill scales at all stages of growth.  Refer to the product label for phytotoxicity and temperature guidelines.  Even after successful treatment, the outer coatings of the scales may remain on the plant material for weeks, which can be unsightly.  The best way to determine if scales are dead is to squeeze them.  They will be dry when squeezed if they are dead and they will ooze liquids if they are living (they were at least alive to the point of being squashed).

For insect identification and additional information on scale control, please see:

A Guide to Scale Insect Identification

UF/IFAS Featured Creatures

Your County Extension Office

What are those scales on my palm tree?

What are those scales on my palm tree?

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.

Potassium and magnesium deficiencies in a canary island date palm.

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

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.