by Matt Lollar | Jan 27, 2016
We may be suffering from the recent low temperatures, but temperate fruit trees such as peaches and apples require a period of cold weather in order to become cold hardy and produce a good crop.
What is Cold Hardiness?
Cold hardiness is the ability of a plant to survive low temperatures. However, every cold event is fairly unique with variables such as when the low temperatures occur (early vs. late winter), how quickly the temperature drops, the temperatures in the days leading up to the event, and the length of time the low temperatures are sustained.
Cold Acclimation
Cold acclimation is the development of freezing tolerance in plants. Three fall environmental factors contribute to cold acclimation in fruit trees. Plant will develop 10 to 15 degrees of cold tolerance when the leaves sense shorter day lengths. Metabolic activity is increased when days are short and temperatures are between 60°F days and 40°F nights. The second factor occurs when lows reach the 20s, which can make trees up to 10 degrees hardier. The final factor occurs when temperatures dip to near zero, which fortunately for us does not occur very often.
Trees remain hardy during the winter as long as temperatures remain fairly stable. However, de-acclimation occurs in reaction to warm temperatures. This explains the winter flowering which occurred this past December. A cold snap may not injure trees unless it immediately follows a period of mild temperatures.
Florida Average Chill Hours Map – UF/IFAS Extension
Chilling Requirement
The cold weather and gradual cold acclimation are necessary to a tree’s accumulation of chill hours which is necessary for steady fruit yields. Chill hours are the accumulation of hours when temperatures are between 32°F and 45°F. The yearly average chill hour accumulation in Northwest Florida is between 660 and 700 hours. The apple varieties recommended for our area (‘Anna’, ‘Dorsett Golden’, and ‘TropicSweet’) have a chilling requirement of 250 to 300 hours. Some of the peach varieties recommended for our area (‘Flordacreast’, ‘Flordaking’, and ‘Gulfsnow’) have a chilling requirement of 350 to 400 hours. Please note the risk of planting these varieties because their chilling requirements are lower than our average chill hour accumulation. The varieties listed are for example, but other available varieties are suitable for our area.
Whether you like winter weather or not, just remember the satisfaction of eating fresh fruit in the summer. To track this year’s chill hours from the warmth of your home, please visit the AgroClimate tool at http://agroclimate.org/tools/Chill-Hours-Calculator/.
by Matthew Orwat | Jan 13, 2016
Crapemyrtle Scale, UF / IFAS Extension
During cold January weather, one doesn’t often think about spraying fruit trees and ornamental shrubs for spring insects and diseases. It’s just not on the radar. The fact is January and February are the best time to apply dormant sprays to combat insect and disease issues. Many ask, “What are dormant sprays” ?
Dormant sprays act on insects or disease pathogens differently. Many insects overwinter on trees and shrubs, either as eggs or immobilized in a protective shell (scale insects). Horticultural oils applied during cool dormant conditions work by smothering the eggs of some insect species or encapsulated scale insects. Since they cannot breathe, they die.
On the other hand, dormant sprays containing copper or sulfur actually kill latent fungal spores that are ready to infect the moment weather warms. They also burn tender young plant tissue, so can only be used when the plant is not actively growing. These preventative sprays can delay disease incidence in early spring and allow for reduction or elimination of regular fungicide applications. The old adage “an ounce of prevention is worth a pound of cure” surely applies to these situations.
There are several products on the market for dormant applications.
Dormant oil is a type of horticultural oil, made of refined petroleum products, for application on trees or shrubs when the trees are not actively growing. It has been in use for over 100 years. They are effective in the suppression of scale insects and mites. Care must be used to not apply them when daytime temperatures are above 75 degrees or night temperatures below 28 degrees. Other horticultural oils exist that can be applied during the growing season to control soft-bodied insects, but not during extremely hot weather. Many different brands exist, some are certified organic by OMRI. They can be purchased at most garden centers, but the best selection is usually found at your independent nursery or farm store.
Cottony Cushion Scale, Image Credit, Matthew Orwat, UF / IFAS Extension
Dormant fungicides can be classified into two groups. Those that contain copper and those that contain sulfur. The most common preventative remedy for fungal disease is lime-sulfur. It is applied to dormant plants and actually sanitizes the stem, killing all fungal spores. It cannot be used during the growing season since it burns leafy tissue. Caution must be taken when mixing and loading since, being an acidic product, can burn the skin. Wear chemical resistant gloves when applying (bought at your local hardware store for $4.00-$10.00), safety goggles and follow all label directions carefully. Also, never apply lime-sulfur within one month of horticultural oil applications. It should be applied in early to mid February, avoiding hard freezes for the 24 hours around application time.
Dormant copper sprays are effective on both bacterial and fungal pathogens and used primarily on fruit crops for the suppression of many fruit diseases including fire blight, bacterial leaf spot, powdery mildew, downey mildew and anthracnose. One popular option, the “Bordeaux Mixture” blends copper with lime. This lime reduces the acidic nature of the copper, thus reducing tissue damage when applied to plants. Always read the label for proper personal protective equipment and dosage rates, to avoid copper toxicity.
For more information, contact your local extension agent or consult these extension publications from: Disease Management Strategies, and Pest Control Using Horticultural Oils .
by Larry Williams | Jan 13, 2016
Pecan trees are well adapted to our area, making beautiful large shade trees. And, if the correct varieties are planted, they can provide pecans.
Only those pecan varieties that show some real resistance to disease problems are recommended for planting here in the humid south. Select grafted trees of Desirable, Curtis, Elliott, Moreland or Stuart varieties.
Pecan leaves and fruit. Photo credit: Brad Haire, University of Georgia, Bugwood.org
Obtain and plant your pecan trees during the winter – December through February. Purchase trees that are three to six feet tall. Larger trees are more difficult to transplant.
Give pecan trees plenty of room to grow. The distance between trees should be approximately sixty feet because mature trees are quite large. Commercial producers sometimes use a closer spacing, primarily because they are using varieties that will bear at an earlier age. But most of those varieties do not have good disease resistance and still require pesticide spray at times. Homeowners will not have the needed equipment to spray a large pecan tree and the drift from such sprays would not be desirable around your home, so commercial varieties aren’t recommended for home plantings.
One of the keys to survival of a pecan tree is not allowing the root system to dry out before, during or after transplanting. Regular watering will be required for a period of at least six months or until the young tree is well established. The planting hole should be 18 to 24 inches wide and only as deep as the root system. Spread the roots so they are not matted together. The planting depth is critical. Place at such a depth that the uppermost root is at or near the soil surface. Excessively deep planting can result in eventual death of the tree.
When planting your tree, there is no need or advantage to using peat moss, compost, manure or other organic matter in the planting hole. Plant the tree in the native soil without amendments.
Do not fertilize when the tree is planted. Wait until May of the first year after planning to apply fertilizer.
Remember that pecan trees are large at maturity, with branches spreading 30 feet or so from the trunk. Also, because of the brittle limbs and failing nuts, it’s best not to plant these trees too near the home, driveway or sidewalk.
by Matthew Orwat | Nov 24, 2015
Satsuma fruit, harvested with their stem intact to ensure longevity when stored. Image Credit: Dr. Pete Andersen
The satsuma mandarin (Citrus unshiu) is a popular dooryard fruit tree, and emerging crop, across the Florida Panhandle. 100-150 years ago it was a major cash crop for the region, with boxcar loads being shipped to the Northeast during the months of October-December. Due to a series of hard freezes in the 1950s and a shift in land use from produce production to timber, the satsuma industry was effectively dead in northwest Florida until recent years, when several entrepreneurial growers have invested time and effort in bringing back this delicious citrus to the commercial scene.
Throughout this time, many homeowners have enjoyed this historic citrus, dressing many a Thanksgiving table with its beautiful bright orange fruit. Satsumas contain few seeds, are generally sweet and very easy to peel. They are part of the mandarin group of citrus, and somewhat resemble canned mandarin oranges in shape and flavor. The cooler the fall temperatures (above freezing) the sweeter the fruit will be at harvest.
Mature trees are hardy down to 14-18 º F when budded to a cold hardy rootstock such as trifoliate orange or swingle. Young trees need to be protected from temperatures below the mid 20s, and fruit will be ruined if exposed to any freezing temperatures below “light frost” conditions. Commercial growers use protective techniques, such as microirrigation, to protect their fruit if freezing temperatures threaten harvest.
This Thanksgiving, if you do not have a satsuma tree of your own, seek out a local producer and buy a case of satsumas for the holiday season !
For more information on growing and harvesting satsuma mandarins consult “The Satsuma Mandarin – HS195“, produced for your benefit by UF / IFAS Extension.
by Julie McConnell | Sep 29, 2015
Giant Swallowtail on citrus leaf. JMcConnell, UF/IFAS
Adult butterflies are pretty easy to attract to your landscape if you provide flowering plants, but getting them to lay eggs in your garden is a little trickier.
Butterflies go through complete metamorphosis which means that they have four main life stages. The first is the egg, second they hatch into caterpillars (larvae) which feed and molt many times, the third stage is the pupa or chrysalis, and finally they emerge as colorful adults. Complete metamorphosis is considered a more advanced life cycle than incomplete and one of the reasons is because most insects that go through this process do not compete for food at different life cycles. For example, the gulf fritillary butterfly larvae needs passionflower (Passiflora spp.) to feed on – no other plant type will do. The adults visit many flowering landscape plants such as zinnias, butterfly bush, pentas, etc. The adults are feeding on nectar while the caterpillars are eating foliage.
Because the larvae are very host specific, you must offer the correct plant to attract particular butterflies. Luckily, we have many options in the Florida panhandle! Just remember if you would like to attract butterfly breeding to your yard, you must sacrifice some foliage to support the caterpillars.
• Gulf Fritillary – Passionflower
• Monarch – Native milkweed
• Giant Swallowtail – citrus
• Eastern Black Swallowtail – plants in the carrot family including dill, celery, fennel, and parsley
• Tiger Swallowtail – sweet bay magnolia, tulip poplar, black cherry
• Zebra Swallowtail – pawpaw
• Luna Moth – walnut, hickory, sweetgum, persimmon, winged sumac
If you would like to know more about individual butterfly species please visit UF/IFAS Entomology & Nematology’s Featured Creatures website.
by Roy Carter | Aug 10, 2015
The muscadine grape is a popular fruit that grows very well here in North Florida. It has smaller leaves than bunch grapes and fruit are harvested singly, rather than in bunches. Theses grapes can be enjoyed fresh and also be used for home wine-making. One of the nice things about growing muscadine grapes in Florida is that they’re rarely bothered by insects or diseases. They can easily be grown in your backyard garden.
Muscadine grapes are ripening now! Photo credit: Mary Derrick, UF/IFAS Extension.
Grapes will grow well in a variety of soils here in North Florida. Upland soils with clay underlying at about three feet are ideal. You should avoid poorly drained soils. If the grapes are grown on soil with very good drainage, they should be set in the ground deeper than they were grown in the nursery on land with a high water table. Grapes should be planted on raised beds at the same depth they were at in the nursery.
During the first year, grapes should be fertilized with a quarter pound of 8-8-8 or 10-10-10 fertilizer, applied in bands about a foot away from the plant, soon after growth begins. Repeat applications in April, July and September. Fertilizer rates increase each year, but they should never exceed six pounds per vine per year.
Weeds can sometimes be a problem with muscadine grapes. To get rid of weeds, you can use a good herbicide, or you can cultivate around the plants. The muscadine grape has a very shallow root system, however, so be careful when you’re weeding around the plants. Mulches can be helpful in controlling weeds, but be sure to leave a circle of at least six inches around each vine uncovered.
Grapes need a generous supply of water to survive here in North Florida. In fact, more first-year grapes die from a lack of water than from any other cause. Make sure the plant receives about an inch of water weekly. Muscadine grapes are rarely bothered by insects or diseases. However, a spray program is advised to protect plants from possible damage by black rot or bitter rot. Spraying should begin when the vines are in bloom, and continue a regular two week intervals until about a week before the harvest. For specific information on the proper spray to use, you should contact your local County Agent.
Muscadine grapes mature in August and early September. If you don’t plan to use them immediately, they should be picked from the vine when ripe and stored at 40 degrees Fahrenheit.
For more information, please see:
The Muscadine Grape
Muscadines Benefit from Timely and Artful Pruning
