by Larry Williams | Jun 23, 2020
The 2020 Atlantic Hurricane Season got off to an early start with some tropical storm activity before the season’s official June 1 start date. We live in a high wind climate. Even our thunderstorms can produce fifty-plus mile per hour winds.
Storm damaged sweetgum tree. Photo credit: Larry Williams
Preventive tree maintenance is key to preparing for storms and high winds.
Falling trees and flying landscape debris during a storm can cause damage. Evaluate your landscape for potential tree hazards. Pruning or removing trees once a hurricane watch has been announced is risky and tree trimming debris left along the street is hazardous.
Now is a good time to remove dead or dying trees, prune decayed or dead branches and stake newly planted trees. Also inspect your trees for signs of disease or insect infestation that may further weaken them.
Professional help sometimes is your best option when dealing with larger jobs. Property damage could be reduced by having a professional arborist evaluate unhealthy, injured or questionable trees to assess risk and treat problems.
Hiring a certified arborist can be a worthwhile investment. To find a certified arborist in your area, contact the International Society of Arboriculture (ISA) at 888-472-8733 or at www.isa-arbor.com. You also may contact the Florida ISA Chapter at 941-342-0153 or at www.floridaisa.org.
Consider removing trees that have low wind resistance, are at the end of their life span or that have the potential to endanger lives or property.
Some tree species with the lowest wind resistance include pecan, tulip poplar, cherry laurel, Bradford pear, southern red oak, laurel oak, water oak, Chinese tallow, Chinese elm, southern red cedar, Leyland cypress, sand pine and spruce pine.
Broken pine from hurricane. Photo credit: Larry Williams
Pine species vary in their wind resistance, usually with longleaf and slash pines showing better survival rates than loblolly and sand pine. However, when pines become large, they may cause a lot of damage if located close to homes or other valuable structures. As a result, large pines are classified as having medium to poor wind-resistance. For this reason, it’s best to plant pines away from structures in more open areas.
Before and after a storm, tree removal requires considerable skill. A felled tree can cause damage to the home and/or property. Before having any tree work done, always make sure you are dealing with a tree service that is licensed, insured and experienced.
More information on tree storm damage prevention and treatment is available online at http://hort.ifas.ufl.edu/woody/stormy.shtml or from the UF/IFAS Extension Office in your County.
by Carrie Stevenson | Jun 4, 2020
Fig. 1 An adult redbay ambrosia beetle compared to the size of a single penny. Credit: UF/IFAS File Photo.
While most bark beetles are important in forest ecology by recycling fallen dead trees and eliminating sick and damaged trees, some of them may impact healthy trees. A group of bark beetles that has become a major concern to forest managers, nurseries, and homeowners is the ambrosia beetle. Ambrosia beetles are extremely small, 1-2 mm in length, and live and reproduce inside the wood of various species of trees (Fig. 1). Ambrosia beetles differ from other bark beetles in that they do not feed directly on wood, but on a symbiotic fungus that digests wood tissue for them. Every year, non-native species of ambrosia beetles enter the United States through international cargo and we have now nearly forty non-native species of ambrosia beetles confirmed in the United States. Among them, the redbay ambrosia beetle (Xyleborus glabratus), originally from Southeast Asia, is the vector of the fungal pathogen causing laurel wilt, a disease that devastated the Lauracaea population in the southeastern USA, killing millions of redbay, swamp bay, sassafaras and silk bay.
Fig. 2: A mature dooryard avocado tree with large sections of dead and missing leaves, caused by laurel wilt disease. Summer 2009 Impact Magazine image. Credit: UF/IFAS File Photo.
When these beetles attack a laurel tree, the symbiotic fungus is vectored to the tree’s sapwood after the beetle has tunneled deep into the tree’s xylem, actively colonizing the tree’s vascular system. This colonization leads to an occlusion of the xylem, causing wilting of individual branches and in a matter of weeks progresses throughout the entire canopy, eventually leading to tree death (Fig. 2). The laurel wilt disease has spread rapidly after the vector was first detected in Georgia in 2002. The redbay ambrosia beetle was first detected in Florida in 2004, in Duval County, attacking redbay and swamp bay trees. At this point, it is estimated that more than one-third of redbay in the U.S.A., 300 million trees, have succumbed to the disease.
Starting in 2017, we examined the efficacy of verbenone against redbay ambrosia beetle in live laurel trees in a natural forest setting. Verbenone is an anti-aggregation pheromone that has been used since the 1980’s to protect lodgepole pine. Verbenone also has the potential to be used over large areas and is currently being used to protect ponderosa pine plantations from the Mountain Pine Beetle in the western US.
We have found verbenone to be an environmentally friendly and safe tool to prophylactically protect laurel trees against redbay ambrosia beetle. Our protocol consists of the application of four 17 g dollops of a slow-release wax based repellent (SPLAT Verb®, ISCA technology of Riverside, CA) to the trunk of redbay trees at 1 – 1.5 m above ground level (Fig. 3). The wax needs to be reapplied every 4 months during fall and winter and every 3 months during spring and fall when temperature is higher. When compared to the control trees without repellents, we found that trunk applications of verbenone reduced landing of the redbay ambrosia beetle on live redbay trees and increased survivorship of laurel trees compared to untreated trees (Fig. 4). Verbenone should be considered as part of a holistic management system against redbay ambrosia beetle that also includes removal and chipping of contaminated trees.
If you have Redbay or other bay species on your property and are concerned about Laurel Wilt Disease or Redbay Ambrosia Beetle damage, contact your local UF/IFAS Extension Agents for help!
This article is courtesy of Dr. Xavier Martini and Mr. Derek Conover of the UF/IFAS North Florida Research and Education Center (NFREC) in Quincy.
Fig. 3: Application of SPLAT Verb on a redbay tree during a field trial
Figure 4: (A): Cumulative capture of redbay ambrosia beetles Xyleborus glabratus following a single application of verbenone vs untreated control (UC). (B) Survivorship of redbay and swamp bay trees treated with verbenone on four different studies conducted in 2017 and 2018.
by Daniel J. Leonard | Jun 2, 2020
Pineapple Guava (Acca sellowiana) hedge. Photo courtesy of the author.
One of the most common questions I’ve gotten across the Panhandle over the last several years is “What can I plant to screen my house and property?” I surmise this has a lot to do with Hurricane Michael wiping properties clean and an explosion of new construction, but whatever the reason, people want privacy, they want it quickly, and they often want something a little more natural looking and aesthetically pleasing than a fence. Like everything else, the answer to the question is nuanced depending on the site situation. However, if the situation is right, I almost always recommend that clientele at least consider a woefully underutilized plant in the Panhandle, Pineapple Guava (Acca sellowiana).
Named a Florida Garden Select Plant by the Florida Nursery Growers and Landscape Association (FNGLA) in 2009, Pineapple Guava is a standout screening and specimen plant, passing all the usual tests homeowners demand from shrubs. Growing 15’x15’ or so if never pruned or sheared, these quick-growing evergreen shrubs sport pretty, leathery green leaves with gray to white undersides. This leaf underside coloring causes the plants to emit a striking silvery blue hue from a distance, a very unusual feature in the screening shrub world.
Pineapple Guava (Acca sellowiana) silvery blue leaf undersides. Photo courtesy of the author.
Look past the leaves and you’ll notice that Pineapple Guava also possesses attractive brownish, orange bark when young that fades to a pretty, peely gray with age. To complete the aesthetic trifecta, in late spring/early summer (generally May in the Panhandle), the plants, if not heavily sheared, develop gorgeous edible, pollinator-friendly flowers. These flowers, comprised of white petals with bright red to burgundy stamens in the center, then develop over the summer into tasty fruit that may be harvested in the fall.
In addition to being a superbly attractive species, Pineapple Guava is extremely easy to grow. They like full, all-day, blazing sunshine but will tolerate some shading if they receive at least six hours of direct sun. Well-drained soil is also a must. Pineapple Guava, like many of us, is not a fan of wet feet! Site them where excessive water from rain will drain relatively quickly. Adding to its merits, the species is not plagued by any serious pests or diseases and is also drought-tolerant, needing no supplemental irrigation once plants are established. A once a year application of a general-purpose fertilizer, if indicated by a soil test, may be useful in getting plants going in their first couple of years following planting, but is rarely necessary in subsequent years. To maintain Pineapple Guava as a formal hedge or screen, a simple shear or two each growing season is normally enough. The species also makes an outstanding small specimen tree when allowed to grow to its mature height and “limbed-up” to expose the interesting bark and limb structure.
Edible, pollinator-friendly Pineapple Guava flowers in bloom. Photo credit: Larry Williams
If you’ve been looking for a quick-growing, low-maintenance screen or a specimen plant for a large landscape bed, you could do a lot worse than the Florida-Friendly Pineapple Guava! As always, if you have any questions about Pineapple Guava or any other horticulture, agriculture or natural resource related issue, contact your local UF/IFAS County Extension Office!
by Matt Lollar | May 20, 2020
The pawpaw (Asimina triloba) is a native edible that is often overlooked and misunderstood. Not only does it produce a delicious fruit that looks like a mango and tastes like a banana, but it is also an aesthetic landscape plant. This fruit is slowly gaining popularity with younger generations and a handful of universities (Kentucky State University and the University of Missouri) are working on cultivar improvements.
A pawpaw tree growing in the woods. Photo credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
The pawpaw is native to the eastern United States (USDA Plant Hardiness Zones 5-8), however it’s closest relatives are all tropical such as the custard apple, cherimoya, and soursop. The pawpaw, along with these fruits, are known for their custard-like texture which may be a unpleasant for some consumers. Pawpaws are relatively hardy, have few insect pests, and can still produce fruit in partial shade (although they produce more fruit when grown in full sun).
Pawpaws perform best in moist, well-drained soils with a pH between 5.5 and 7.0. They are found growing wild in full to partial shade, but more fruit are produced when trees are grown in full sun. However, pawpaws need some protection from wind and adequate irrigation in orchard settings. Trees can grow to between 12 feet to 25 feet tall and should be planted at least 15 feet apart. In the Florida Panhandle, flowers bloom in early spring and fruit ripen from August to October depending on variety and weather.
Young pawpaw fruit growing on a small tree. Photo Credit: Matt Lollar, University of Florida/IFAS Extension at Santa Rosa County
A number of improved cultivars of pawpaws have been developed that produce more fruit with more flavor than native seedlings/saplings. The University of Missouri has conducted trials on the following pawpaw cultivars: ‘Sunflower’; ‘PA Golden’; ‘Wells’; ‘NC-1’; ‘Overleese’; ‘Shenandoah’; ‘Susquehanna’; and ’10-35′. Most of these cultivars performed well in southern Missouri, however yields may differ in the Florida Panhandle. The full results of the trial can be found in the “Pawpaw – Unique Native Fruit” publication.
Pawpaws can be propagated by seed or cuttings. Unlike most fruit trees, pawpaws are usually true to seed meaning that saved seed produces a tree with similar characteristics to the parent tree. To save seeds, place fresh seeds in a bag of moist peat moss and refrigerate for 3 to 4 months before planting. To vegetatively propagate, take cuttings (pencil thin in diameter) in the winter and store in a refrigerator until early spring. Cuttings should be chip budded onto seedling rootstock during the spring. Please visit this publication from the University of Nebraska for more information on chip budding.
Pawpaw fruit are ready to harvest when they are slightly soft when gently squeezed. Fruits picked prior to being fully ripe, but after they start to soften, will ripen indoors at room temperature or in a refrigerator. Already-ripe fruit will stay fresh for a few days at room temperature or for a few weeks in the refrigerator. To enjoy pawpaw fruit throughout the year, scoop out the flesh, remove the seeds, and place the flesh in freezer bags and freeze.
Whether you want to add more native plants to your landscape or you are a rare and unusual fruit enthusiast, pawpaw may be the tree for you. They can be utilized as a focal point in the garden and provide delicious fruit for your family. For more information on pawpaw or other fruit trees, please contact your local Extension Office.
by Larry Williams | May 14, 2020
When we go through dry periods in North Florida some residents become interested in drought-tolerant plants to include in their landscapes. The need for irrigation can be reduced when drought-tolerant plants are used. But don’t overuse these plants. Remember we have periods of rainy weather, too.
Gulf Muhly Grass in Flower. Photo credit: Larry Williams
Some drought-tolerant plants have poor tolerance to the other extreme – too much water. There are a few plants that can tolerate both extremes but they are the exception. Avoid using drought-tolerant plants on naturally wet or poorly drained sites. But if you have the typical deep sandy well drained soil Florida is famous for, you’d do well to include some drought-tolerant plants on your site.
Drought-tolerant plants are especially well suited for areas that receive little to no irrigation.
Some plants are genetically better able to withstand drought. They have a built-in tolerance of drought. Many of our Florida native plants are designed to grow in our poor water holding sandy soils. Many of the plants native to arid areas of the world possess high drought-tolerance. These plants have characteristics that allow them to better survive dry weather. These features include thicker or waxier leaves, large surface root areas or deep roots and the ability to drop leaves in drought and regain them when moisture is adequate.
Beautyberry with fruit. Photo credit: Larry Williams
It’s important to realize that these plants must first establish a root system before they can cope with severe dry weather. Plan to irrigate during dry periods for the first season to allow them to become established.
Some outstanding trees to consider include crape myrtle, redbud, Chinese pistache, cedar (Cedrus species), hawthorn (Crataegus species), American holly, yaupon holly, Southern red cedar (Juniperus species), Live oak, Sand live oak, winged elm, pond cypress and bald cypress. Some people are surprised to learn that pond cypress and bald cypress have high drought-tolerance because these trees are associated with swamps, many times growing in standing water. But once established on a dry site, they exhibit very good drought-tolerance.
Some outstanding shrubs with drought-tolerance include glossy abelia, dwarf yaupon holly, Indian hawthorn (Rhaphiolepis species), beauty berry (Callicarpa americana), pineapple guava, junipers, oleander, spiraea, blueberry or sparkleberry (Vaccinium species), viburnum, Chaste tree (Vitex agnus-castus) and coontie (Zamia pumila).
Pineapple guava in bloom. Photo credit: Larry Williams
Some outstanding drought-tolerant groundcovers to consider include beach sunflower (Helianthus debilis), daylily, juniper, lantana, liriope, rosemary (Ceratiola ericoides), Asiatic jasmine and society garlic. Many of the ornamental grasses such as Gulf muhly are good choices as well.
For more ideas on developing a Florida-friendly, water wise landscape, contact the UF/IFAS Extension Office in your County or visit the below website. https://ffl.ifas.ufl.edu/index.html
by Mark Tancig | Apr 30, 2020
Symptoms of oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
Even during global pandemics, it’s a joy to be outside during the great north Florida spring we’ve been experiencing lately. As cold fronts come through with their rain bands, some packing a punch, they leave behind the most pleasant mornings, clear blue daytime skies, and crisp evenings. Unfortunately, we’re not the only organism that also enjoys those cool days. Many species of fungi are quite active this type of year as the rains, followed by warmer, yet not too hot temperatures, create the perfect conditions for fungal growth. Some of these fungi grow right on or in the plants we’d like to be enjoying for ourselves, stealing nutrients and causing plant decline or merely causing aesthetic damage. As this is an active time for certain species of fungi, local extension offices are getting more calls and questions regarding lawn and landscape damage due to fungal pathogens. A recent call was a new one for me and an example of a native fungi-plant interaction that looks bad but requires no intervention from us. It also highlights how correctly identifying a disease leads to the best action and can often save time and money and prevent unnecessary pesticides (in this case a fungicide) from entering the environment.
Close up of oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
The fungi and plant involved here was the oak leaf blister (Taphrina caerulescens) on a swamp chestnut oak (Quercus michauxii). It forms, you guessed it, blisters on the leaves of any of the oaks, though live oak (Quercus virginiana), laurel oak (Quercus laurifolia), and water oak (Quercus nigra) seem to be preferred hosts. The spores of the fungi, dormant since the previous summer/fall and which happen to get lodged in bud scales through wind and rain, germinate in cool, wet weather. The fungus then infects young leaves as they flush and its growth causes a disruption in the leaves’ development. This leads to the blistered look of the leaf tissue and, during extended periods of cool, wet weather, the entire leaf sort of shrivels, browns, and eventually falls off. Spores are eventually released from the fallen leaves to start the process over the next spring.
Severe oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
Though the leaves look pretty terrible, this fungal disease rarely causes plant health issues and the tree recovers just fine. Specimen trees that experience it year to year may be treated with a fungicide, but most homeowners can just let it go. Raking up and disposing of the leaves may help prevent further infections by reducing the number of spores released in the area.
As you enjoy another cool morning after an evening rainstorm, remember that the fungi all around you are also having a great day. You may want to look at your landscape plants and see if there’s anything abnormal going on. If so, take a photo and send it to your local extension office for help with identification and best methods of control, or, like in this case, just leaving it alone.
p.s. As I said this was a new one for me and I want to thank Stan Rosenthal, Extension Agent emeritus, for assisting with identification.
