by Roy Carter | Oct 28, 2014
Split citrus fruit. Image credit UF / IFAS
Citrus trees require a lot of care and attention to produce good quality fruit, yet even the most careful gardeners may run into the problem of split-fruit on their citrus trees. Split-fruit is a condition which strikes citrus trees in September and October and can wipe out a hundred or more fruit on a single tree. Researchers at the University of Florida have been studying fruit splitting for many years. Clear cut causes or solutions have not been found. My information on fruit splitting was provided by Extension Fruit Crop Specialist, Dr. Pete Andersen with IFAS located at Quincy, North Florida Research and Education Center.
Researchers have found that certain varieties of citrus tend to split more often than other. “Sweet Oranges” Tangelos” and certain varieties of Satsuma’s tend to split more than citrus which is not sweet. Grapefruit and acid fruits, such as lemons and limes rarely split.
The condition is known to be more common in seedlings and young trees than in older, more settled trees. However, split-fruit can be a very serious problem when it occurs on mature trees, because they usually have more fruit to lose.
Another condition which will cause fruit to split is insufficient copper in the soil. This used to be a much greater problem than it is today, due to the wide-spread use of copper in most fertilizer and spray programs. Potassium deficiency results in small, firm fruit with thin peels and increased fruit splitting. However, added potassium doesn’t correct splitting related to citrus varieties.
The most commonly held belief is that fruit splitting is caused by climatic conditions, since it only seems to occur at one time of the year. During the late summer and high humidity, followed by periods of drought. After a series of heavy rains, the trees absorb a great deal of moisture and force it into the fruit. Since the fruit is near maturity, the rind becomes less pliable and can’t expand rapidly enough to absorb the great volume of water from the trees. As a result the fruit splits.
Despite these findings, there are numerous cases of fruit splitting that doesn’t appear to be related to any of the above conditions. When the cause of the split is not fully understood, there is not absolute method of control. Also, there is no way to stop fruit splitting while it is occurring. The problem must be prevented before it starts. Attempts to control splitting through irrigation practices, fertilization and growth regulators have met with some success.
Fertilizer and irrigation practices won’t cure splitting, but may help to avoid large increase in the number of split fruit. In addition, growth regulators are available which can thicken the peel of the orange. Thicker peels have been found to split much less often that the thinner peels, due to their ability to withstand extra water pressure during the critical moths of the year.
If fruit splitting is a problem this year follow a recommended fertilizer program next year. This will insure a good supply of minor nutrients, especially copper. Make sure to keep the trees well watered during the dry periods of late summer and early fall. This will keep the fruit from swelling too rapidly, and splitting as a result.
by Matthew Orwat | Sep 16, 2014
Prolific producing muscadine cultivar ‘Granny Val’ – Image Credit Dr. Peter C. Andersen
Mother always said “never be late” but in the case of certain muscadine (Vitis rotundifolia) cultivars, it’s good to be late.
Although muscadine harvest can begin as early as July, gardeners with late bearing muscadines are still reaping the benefits of fruit harvest and may until early October.
Northwest Florida gardeners often grow muscadines as a substitute for traditional grape (Vitis vinifera) cultivars such as ‘Concord’ or ‘Thompson’s Seedless’, since they are prone to Pierce’s Disease. In fact, muscadines are native to the southwest USA and resistant to a variety of insect and disease pests, so much so that they can be grown in the home garden without the use of insecticides or pesticides.
An additional advantage of gardening with muscadines is that they can easily be asexually propagated. To mimic the natural asexual propagation of wild muscadines, home gardeners may use the pegging method. Pegging entails wounding the branch in several locations, then burying the wounded section of the branch in moist soil while leaving the shoot tip exposed. If this is done in the late spring or summer, roots should form from the main branch in about a month. After roots are confirmed, the connection with the mother plant can be cut.
Planting time for muscadines depends on the type of plant purchased. If gardeners want to plant bare root vines, they should plant them between December and January, but containerized plants can be planted any time.
Before muscadines are planted, soil tests should be performed to determine pH. Muscadines can be grown in the pH range of 5.5 to 7.0, with the optimal level between 6.0-6.5. Since many soils in northwest Florida are highly acidic, tests should be done at least 3 months before planting. This will allow the addition of an optimal lime source Dolomite, which takes 3 months to raise the pH but also adds magnesium to the soil.
If this article prompts the reader to plant muscadines, refer to HS # 753 “The Muscadine Grape” for information about establishment, irrigation and fertilization.
Here is a list of recommended late bearing cultivars to look for when selecting plants.
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Big Red
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Delight
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Doreen
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Farrer
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Granny Val
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Late Fry
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Nesbitt
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Polyanna
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Supreme
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Pineapple
by Matthew Orwat | Jul 8, 2014
Cedar-Apple rust or Cedar-Quince rust (Gymnosporangium) symptoms on pear fruit. Image Credit Shep Eubanks, UF IFAS.
This is the season for fruit harvesting, particularly for those fruits in the rose family such as plum, quince, peach, pear and apple. Many avid home horticulturists have been enjoying the fruits of their labor, but some have been thwarted by an unlikely and ugly disease.
This fungal disorder, commonly called cedar-apple rust and caused by various species of Gymnosporangium, has the potential to ruin Quince, Pear and Apple crops in gardens throughout Northwest Florida. Early scouting and vigilance will pay off.
This condition begins on native juniper species (known as cedars). A spore producing gall forms on the branches of the cedar tree, which begin to produce spores during wet weather. Spores, once produced, can travel up to a mile via wind. If spores land on susceptible plant tissue when a film of water is present, it will germinate and infect the fruit, twig or leaf. Although black spots develop on the plant with in 7-10 days of infection, orange tubes called aecia won’t develop until 4 or more weeks after infection. Next, spores are released from the aecia located on the fruit tree and travel to infect new juniper plants . The infected junipers will not show symptoms until the next growing season but they can manifest as galls or orange ooze present under bark. Different species of Gymnosporangium will infect trees differently. Some live only for one year while others, known as ceder-quince rusts, can last up to 20 years. Twigs infected with this disease usually die within several years of infection.
Ceder-Apple Rust on infected juniper host species. Image Credit Hank Dankers UF IFAS.
Although this may seem like an impossible situation, several control strategies exist.
- Remove Infected branches: Removal of infected plant tissue will reduce the spread of the disease in your garden.
- Removal of infected juniper host species: If the juniper or “cedar” in your landscape is something you can sacrifice, removal is warranted in cases of heavy infection.
- Avoid planting susceptible species of juniper next to susceptible fruit tree species.
- Treatment of fruit trees with fungicide: Preventative fungicidal sprays of products containing the active ingredients of sulfur, captan, chlorothalonil, or mancozeb and similar products can be effective. They will not cure existing conditions but are useful if you know that rusts are present in your area. Please read all pesticide labels before application, since there are pre-harvest limitations present on some products.
For additional information, please consult you local county extension office or review these publications by UF IFAS specialists (Florida Plant Disease Management Guide) and the Missouri Botanical Garden.
by Julie McConnell | Jul 1, 2014
Panhandle residents have seen caterpillars in abundance this June. One common visitor to pecan trees is the Walnut Caterpillar Datana integerrima. The walnut caterpillar has a very narrow host range and feeds only on trees in the Juglandaceae family which includes walnut, pecan, and hickory trees. They are sometimes seen on other plant material, but feeding on non-host plants is unlikely.
Walnut caterpillar feed on the leaves of host trees through several growth stages and molts until they have reached the final larval instar and are ready to pupate into an adult moth. Their color changes from light green when newly hatched to reddish-brown to almost black with long white hairs as they mature. The caterpillars group together in large masses and may hang from each other and dangle from the tree branches when molting. Instead of creating a cocoon in the tree, the walnut caterpillar moves to the ground beneath the tree and burrows into the soil or leaf litter to pupate and emerges later as a moth.
What can you do if your pecan tree is hosting walnut caterpillars?
Although the numbers seen on trees may be alarming, a healthy tree can tolerate some feeding damage. Stripped branches may increases the chance of a lower yield of fruit because the removal of leaves does reduce the amount of energy the tree can produce, but overall health of the tree should not be significantly affected. However, many homeowners find falling caterpillars and their excrement unappealing and may decide to take steps to manage the population.
There are several natural enemies that feed on caterpillars, so avoid using a broad spectrum insecticide that might harm predatory insects and other animals. Consider using a biological control product such as Bt (Bacillus thuringiensis) that is only lethal to caterpillars. Other methods are “pick and squish” or drowning in a bucket of soapy water. Next year, in the spring, watch for masses of tiny green eggs on the underside of leaves and remove and destroy them before hatching.
For more information visit USDA Forest Service Forest Insect & Disease Leaflet 41 “Walnut Caterpillar”
by Gary Knox | Jun 17, 2014
Orange flowers and purple fruits often occur on Purple Sunset pomegranate at the same time, producing a colorful display. Photo by Gary Know, UF IFAS.
Purple Sunset is a new ornamental cultivar of pomegranate, Punica granatum. Purple Sunset pomegranate is distinguished from fruiting pomegranate by a bushy, compact habit and numerous flowers followed by small, ornamental, purple-black fruit.
Native to southeastern Europe and Asia, pomegranate has long been grown for its edible fruits. Horticulturists recently recognized its ornamental qualities and began selecting pomegranate for form, flowering, and ornamental fruits. ‘PIIPG-1’ is a cultivar selected from open-pollinated seeds of Punica granatum ‘Nana’. Trademarked as Purple Sunset, this cultivar has a bushy, compact growth habit. Although promoted as a dwarf form that grows only 3–4 feet, plants in north Florida (USDA Cold Hardiness Zone 8b) have grown significantly larger, approaching 6 feet in height 3 years after planting. Purple Sunset pomegranate may be used in the landscape as a specimen plant or hedge.
Leaves of new growth are red-tinged, becoming glossy green throughout summer, and turning yellow to yellow-green in late fall before dropping in early winter. Large two-inch orange flowers occur on new growth throughout summer and fall. The orange flowers develop into inedible, shiny, purple-black fruit up to three inches in diameter. Orange flowers and purple fruits often occur on the plant at the same time, producing a colorful display. Fruits persist into winter, adding interest to the leafless shrub, before eventually falling. Wildlife may eat the tough, seedy fruits, but this has not been documented.
Purple Sunset pomegranate in North Florida. Photo by Gary Knox, UF IFAS.
Culture of Purple Sunset pomegranate is similar to fruiting pomegranate. This plant is hardy in USDA Cold Hardiness Zones 7–10. It grows best in full sun to part shade on deep, loamy soils but is adapted to all but alkaline soils. Pomegranate is somewhat drought tolerant once established. Hedged plants should be pruned in late winter before new spring growth. Leaf spot and fruit blotch, diseases of fruiting pomegranate, may also affect Purple Sunset, but these problems have not been noted in the landscape.
For more information:
The Pomegranate
by Roy Carter | Jun 10, 2014
Blueberry. Photo credit: Eric Zamora, UF IFAS.
Blueberries are native to Eastern North America. They are one of the few crop plants that originated here. The rabbiteye blueberry occurs mostly in certain river valleys in Northern Florida and Southeastern Georgia. The high bush blueberry is native to the eastern third of the United States and Southeastern Canada. Florida is rich in other native species. The woods and swamps of Florida are populated with at least eight wild blueberry species. No area of the state lacks wild blueberries, except where soil pH is above 6.0.
The two types of blueberries grown in Florida are Southern highbush and rabbiteye. The earliest ripening southern highbush varieties ripen about 4 to 6 weeks earlier than the earliest rabbiteye varieties grown at the same location.
Some rabbiteye varieties recommended for our area are: Alice blue, Beckyblue, Climax, Bonita, Brightwell, Chaucer and Tifblue. Some recommended Southern Highbush varieties are: Blue Crisp, Gulf Coast, Jewel, Sharpblue, Santa Fe, Star and Misty.
Blueberries need a fairly acid soil; a pH range of 4 to 5 is suggested. Blueberries grown on alkaline or deep sands will grow poorly. If you need to lower the soil pH before planting, mix in some acidic peat moss.
Blueberries have a shallow, fibrous root system. That means plants should be placed in the ground about an inch deeper than they were growing in the nursery. Rabbiteye blueberries grow poorly in soils with excessive drainage. But they won’t tolerate too much moisture for long periods of time either.
Blueberries are very sensitive to fertilizers. During the first growing season, no mineral fertilizer should be added at all. In the second season, apply about two ounces of an acidic fertilizer per plant. Blueberries can use the same fertilizer as camellias and azaleas, but be careful not to overdo it. Excessive amounts of fertilizer will kill the plants.
Before planting blueberries, you should cultivate the soil by plowing or roto tilling to a depth of at least six inches. Dig a hole large enough so that the roots won’t be crowded. Lightly pack the soil around the roots and water thoroughly. Keep in mind that newly set plants need a good water supply.
Bare-root bushes should be transplanted during the winter months; container grown bushes can be transplanted anytime. The first year after planting, the blossoms should be removed to help the bush grow more quickly.
Pruning is an important part of blueberry culture. It promotes the growth of strong wood, and rids the tree of weak twiggy growth. The strong wood growth is necessary for good fruit production.
Believe it or not, the worst pests of blueberries are birds. You need to protect your bushes with some kind of netting, or employ the old fashioned scarecrow to do the job. It you don’t protect your bushes, you can count on the birds getting to the fruit before you do.
Other than birds, rabbiteye blueberries have few pest or disease problems. Powdery mildew can occur on bushes that don’t get full sun, but this problem can be easily controlled with a sulfur spray. Bud mites, thrips, fruitworms, and defoliating insects can sometimes be a problem.
Weeds will compete with young blueberry bushes for nutrients and water, so keep the beds as free of weeds as possible. Mulches are good for controlling weed growth. If necessary, there are herbicides available.
For more information please see:
Blueberry Gardener’s Guide
