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Tropical Fruit Club Newsletter
October 2007
Officers:
President: Ervin Jannsen Vice President: Abe White Treasurer: Lincoln Lai Secretaries: Joann Maynard,
Pete von Lersner, Heidi Flinchbaugh Newsletter & Mailing: Pam Flesher Refreshments: Yolanda Curtis Librarian: Shirley Silvasy
September Meeting Minutes
Vice President, Abe White, called the meeting to order at 7:05 p.m. There were no minutes from the August meeting as it was a special event. Lincoln Lai read the treasurer’s report. Report approved as read by the membership.
Old Business: The order for the Clip & Pick Fruit Picker is being placed. Pricing approx. $46. which includes postage. Check with Roberta if interested in placing an order.
Doyle Abbott provided the latest information on the Henry Nehrling Society. The society is trying to purchase the Nehrling property. Recently the seller indicated that an agreement had been reached although additional funds are still needed. According to Abe White, the Nehrling Society will be the featured speaker in October so there will be ample opportunity to make direct donations. http://www.nehrlinggardens.org/
A general thanks went out to all of the August event organizers.
Dick Smith reminded members to RSVP for the Oct. 20th “Tour of the Jungle”. The event will take place at his home from 10 am to 3 pm (maps were passed out during the meeting).
New Business: None
Announcements: September 22 the Central Florida Orchid Society will have their annual auction at Leu Gardens. September 29, there will be a plant sale in Downtown Sanford. October 5, 6, & 7 Tropiflora in Sarasota will have their annual plant sale.
Guest Speaker: Tony Owen from Sunniland Corporation presented their new products and talked about current trends and future restrictions.
Members and guests enjoyed the tasting table. Plant raffle winners were drawn and the meeting adjourned.
Orange County Household Hazardous Waste There will be a household hazardous waste collection spot located at 1111 Rock Springs Rd., in Apopka, on October 20, 8 a.m. to 3 p.m. The permanent location is at
5000 L. B. McLeod Rd., in Orlando. The Transfer Station is open every day but only takes household hazardous waste on Wednesdays and Saturdays from 8 a.m. to 3 p.m. For further information please call 407-245-0931.
October 13 & 14 Winter Park Autumn Art Festival in Central Park on Park Ave. in downtown Winter Park. Hours: 9 a.m. to 5 p.m.
October 20 & 21 Maitland Rotary Art Festival surrounding Lake Lily on 17-92 in Maitland.
Hours: 9 a.m. to 5 p.m. both days. Contact info: 407-263-5218
October 20 Jungle Tour & Lunch at the home of Richard and Ronita Smith, 4209 Lake Lockhart Dr., Orlando. From: 10 a.m. to 3 p.m. Lunch will be provided but if you would like to bring a tropical dessert that would be fine. Iced tea and coffee will also be provided, should you want something else to drink bring it with you.
Adults only please. RSVP Richard at 407-298-2620.
13th Annual Mount Dora Plant & Garden Fair, located in downtown Mount Dora. Garden market with more than 15,000 rare and unusual tropical and landscape plants and flowers, as well as furniture, birdhouses and items for the garden. Hours: Saturday 9 a.m. to 5 p.m. Sunday 9 a.m. to 4 p.m. sponsored by the Mount Dora Library Association. Contact: 352-357-4116 or MDPandGFair@aol.com.
Summer 2008
Clyde and Phyllis may lead another
trip in 2008 after schools are out and before the hurricane season. The trip
will be about a week in southwest Costa Rica off the usual tourist trail. We
will visit 3 kinds of tropical gardens, pineapple farms, oil palm operations, a
coffee farm, stone balls of ancient peoples, and the old banana port of Golfito
and area. Plans are not final but if a limit of 20 people are interested, we
hope to show you something different in Costa Rica. Hopefully, we will have time
for a city tour of San Jose. As usual, this will be a fun bunch, so groaners and
complainers need not apply.
We are in Panama now and will see you at the November meeting. Saludos, Clyde
and Phyllis
September Tasting Table Thank You to:
Yolanda Curtis Lentil Soup Kim-Do Lonsdorfer Starfruits & Blackberry Juice
Lincoln & Daphne Lai Fried Rice and Carambolas Heinz Wutscher Tamarind
Heidi Flinchbaugh Cream Cheese & Olive Pin Wheels Mort & Luzmin Garcia Sweetened Cassava
Dom & Veronica Cabrera Ukoy Fritters Virgil Morar Orange Cake
Dr. Benny Oriental Snacks Kathy Batt Jackfruit Ice Cream
September Raffle Table Thank you to:
Adrian Novenario Sugar Cane Mort Garcia Copper Plant
Lincoln& Daphne Lai Banana Plants Pam Flesher Avocados
LAST CHANCE to join Group Order for CLIP’N PICK! These pole mounted fruit pickers drop the fruit right into self-contained bag. $46 with estimated Sales Tax & Freight; Freight is much more reasonable with a group order. For additional information check this link: http://www.frostproof.com/catalog/m9735.html
To order contact Roberta Witherspoon at 407-363-9921 before sending your check.
Volunteers Needed
It is time to elect new club officers for 2008. Please think about what position you would like to serve.
Pam needs help with the newsletter. She needs someone to get it printed and mailed each month. Please let her know if you can help. A volunteer is also needed to keep the club roster up to date.
Websites of Interest
Organic Fruit http://organicfruitofthemonthclub.com
Orange County ExtensionCenter http://ocextension.ifas.ufl.edu
Central Florida Yards and Neighborhoods http://cfyn.ifas.ufl.edu
EDIS (repository of current UF horticulture publications) http://edis.ifas.ufl.edu
Part 2 Oriental Persimmons in Florida1 E. P. Miller and T. E. Crocker2 Irrigation: Established persimmon trees are quite drought tolerant, especially when propagated on the native stock, D. virginiana. Leaf wilting usually does not occur during a 6 week dry period. The quantity of irrigation water and when to apply it depends on the frequency and amount of rainfall, the type of irrigation system used and the soil type. More frequent irrigations will be required on sandy soil than on clay or organic soils. Newly planted trees will often need biweekly waterings. D. virginiana as a rootstock has a widespread root system and is able to tolerate dry conditions once established. The roots will also withstand submersion for periods of up to a week. The tree may shed its leaves, but will usually recover. Phytophthora root rot may at times cause problems on wet soils. Microjet or drip are good types of irrigation which allow fertilizer injection. Microjet will provide cold protection by freezing water around the trunk on cold, still nights. It can also be used to cool the southeast side of trunks which are warmed by the winter sun and sometimes damaged during freezing nights late in the dormancy period.
Fertilization: Although fertilizer requirements for persimmons have not been studied extensively in Florida, recommendations based on practices in other parts of the world, especially Japan, can be made. Trees should be fertilized 3 times a year; in March when still dormant or about 2 weeks before foliation, in June, and again in late August to early September. Generally, after 7 to 10 years a tree will reach good production and will need the highest rate of fertilizer. For mature trees, nitrogen and potassium are applied at 100 to 120 lb per acre or ¾ lb per tree of each element every year. During the first application 50% of the rate is used with 25% applied in the two subsequent applications. Nitrogen in nitrate form is limited because it's rapid availability may promote fruit drop. Phosphorus should be supplied at 50 lb per acre or 3/8 lb per tree annually. It can all be applied in the spring application. Magnesium should be used at 30 to 50 lb per acre applied with the first application or split between the three. A good fertilizer mix for persimmons in peninsular Florida for the spring is ¾ lb of 46% urea, 1½ lbs of sulfate of potash magnesia, ¾ lb of triple super phosphate and ¾ lb dolomite, dependent on pH, applied to a mature tree. June and August fertilizing should consist of ½ of a lb of a 1 to 2 mix of 46% urea and sulphate of potash magnesia. Generally, 7½ to 10 lbs per tree of a 10-10-10-3 NPK Mg fertilizer can be applied annually using the 3 application times at the 50, 25, 25 percentages. Spring planted trees are not put on the regular fertilizer schedule but are fertilized only lightly during the first growing season. One-year-old trees are fertilized at one eighth the rate for mature trees or about ¾ lb of this fertilizer applied in 3 applications at the 50, 25, 25 percentages. Each succeeding year of tree age this fertilizer dosage is increased by ½ to 1 pound. Native D. virginiana in Florida grows best on soils with pH of 6.0 to 7.0. Where pH is below 6.0, lime should be used to raise the pH to 6.5. In high pH soils, generally those over 7, iron and manganese problems can occur. Lack of iron will show up as intervenial yellowing and in severe cases whitish, yellow leaves. Magnesium deficiency can occur from high potassium or calcium levels. Stunted and blackened terminal leaf tips are indications of magnesium deficiency. Fertilizer studies in Japan show nitrogen to increase flower production and is generally the most important element. Potassium appears to promote shoot growth, high phosphorus levels increase fruit color, and magnesium aids in the production of seed.
Training And Pruning: Modified Central Leader Most persimmon trees in the United States are trained to the modified central leader system. Under this pruning system, trees approach the natural growth shape of an unpruned tree. Pruning should allow a density of 145 trees per acre with 15 ft between trees and 20 ft between rows. The main upward shoot is cut back or modified to force lateral growth of side shoots. Three to 6 branches are encouraged, starting 3 ft from the ground and up to 4 ft above that point. The branches should radiate around the canopy circumference and initiate from points not adjacent to one another. The final shape of the canopy is a broad-based, rounded-top pyramid. Second year winter pruning consists of selecting lateral branches fitting the pattern and removing those which formed in the wrong places. Upright shoots that have narrow crotch angles are pruned out because they will not be strong enough to hold fruit loads. The central leader is trimmed back about 1/3 and the terminals of selected shoots are cut slightly to encourage further branching. Third year winter pruning follows the same pattern as second year pruning along with removing inside or vertical limbs which cross or rub each other. Twig terminals and some side shoots on main lateral branches should be left unpruned. This pattern is followed each successive year. The height of the tree is limited by cutting off strong growing sprouts and the vertical growth of the central leader or any lateral branch. As the tree gets older, the fruiting portions tend to spread farther from the center. It is necessary to cut back some limbs providing more branching and fruiting terminals the following year. Attention must also be paid to thinning the canopy for light penetration. Pruning must maintain a balance between fruiting and vegetative vigor. Generally, not a lot of wood needs to be pruned from persimmon trees.
Palmette System: This system affords a greater yield per acre. It works well for persimmons, peaches, apples and pears in other countries. Trees can be planted 15 ft. in rows and 10 ft between the rows giving 290 trees per acre. The tree is flattened down the row and simulates the shape of a palmetto palm leaf. Limbs are supported along 3 or more horizontal wires in the center of the row running 3 to 3½ ft, 6 to 6½ ft, and 8½ to 9 ft parallel to the ground. The first two limbs are established opposite each other at 2 to 2½ ft, in line with the wires and spread out at 45 degree angles from the trunk. Two limbs are formed at each 2 ft interval. All limbs are attached to the wires as they meet them. Young branches can be spread to a 45 degree angle by using a spacer between the trunk and branch. Limbs can be spread by pulling them with a string attached to the ground or by hanging dirt filled plastic bags around them such that the bag's weight forces the limb down. Two end posts 14 ft x 6 in are placed 4 ft in the ground in the row center 7½ ft back from the last planted tree. These posts are set in concrete and lean at an angle with the bottom 12 inches closer to the first tree than the top. The measurement is taken at the bottom of a plumb line hung from the top of the pole. Brace posts 14 ft x 4 in are placed 4 ft. deep every 60 ft in the row. Lengths of high-tensile 12½ gauge fence wire, such as USS Max-Ten 200, are strung through drilled holes in the poles or fence staples placed at the required height. Each wire is tensioned to 250 lbs and fastened to a 6 ft x 4 in tieback post set in concrete at a 45 degree angle 12 ft from each end post. This structure will hold fruit loads and improve fruit quality due to better sunlight exposure. It forms a structure for pulling cold protection material over the trees forming a tent which acts as an insulating blanket. The spun-bound-poly, plastic sheeting, or other material is stored in the row centers during critical times and removed after danger has passed. Growing trees in this manner is more costly, but helps to increase profits.
Flowering, Pollination, Fruit Drop and Seed Set: Flowering: Most cultivars bear only female flowers in which the stamens do not have pollen for fertilization. To set seed in fruit, a cultivar must be pollinated by either male flowers or perfect flowers in which both the ovary and stamens are functional. Since perfect flowers are rare, they are not significant in pollination. Native persimmons will not pollinate the oriental type. Male flowers are smaller than female flowers and are born on weak axillary stems with two to three flowers per cluster. Female flowers are single, surrounded by a large calyx and developed in the axis of the first leaves as the shoot expands in spring. Perfect flowers are intermediate in size. They may be in the center of a male cluster or borne singly in a leaf axis. Pollination: Several cultivars have been selected for large amounts of annual male flower production and crop pollination. They are all pollination variant and small-fruited. `Gailey', `Zenjimaru', `Akagaki' and `Omiya Wase' are of this type. `Gailey' is the most common in Florida and provides sufficient bloom overlap to serve as a male for all cultivars. The two large fruited astringent cultivars, `Nishumura Wase' and `Komasoskie', can also serve as pollinators although male flower production is not as great. Male flowering occurs on a few of the non-astringent cultivars. A moderate amount is often seen on `Hanagosho', `Shogatsu' and some of the `Fuyu' types.
Fruit Drop: Shedding of persimmon fruit can occur at various times throughout the growing period. The first drop is after petal fall and continues for 2 to 3 weeks. This post-bloom drop tends to bring crop loads down to a supportable level. Lack of pollination and seed formation may be factors contributing to the drop. A second fruit drop may occur in June. Research in Japan indicates that lack of sunlight in the canopy area and vigorous vegetative growth may be contributing factors. Vegetative growth may be encouraged due to the summer rainy period common in Florida. Summer fertilizer applications should not include high amounts of readily available nitrogen which encourage vigorous vegetative growth. Drops can also occur July, August, or September, but are not as regular as the previous two. The drops occur more with some cultivars than with others, but do not necessarily occur every year. Pollination, vegetative growth, lack of sunlight, disease pressures, rootstock interactions, soil conditions or heavy cropping the previous year may be contributing factors.
Seed Set: Generally, the astringent cultivars are better than the non-astringent ones at holding and ripening crops of seedless fruit. `Tanenashi' and `Hiratanenashi' seldom set seed even when pollen is available. Commercial, non-astringent orchards in many parts of the world use a pollinator ratio of 1 pollinator tree with every 8 to 16 trees, equally placed throughout the orchard. The more pollen produced, the better the pollinating conditions, and the more honey bees, bumble bees, and other insects that transfer pollen, the greater the seed numbers in the fruit.
Although seed production is desirable to prevent fruit drop, it is undesirable for other reasons. Heavy seed production relates to overfruiting and is known to weaken trees and increase chances for alternate bearing. Generally in Florida, non-astringent orchards have used a very low pollinator ratio, 1 to 20-40 trees. This adequately matures sufficient crop loads with 2/3 of the crop seeded and containing 1 to 3 seeds per fruit. Sufficient seedless crop loads in Florida on many of the non-astringent cultivars have been observed, but yields have not been studied over a many year period. Seedless or near seedless production may be advantageous in reducing the need to hand thin the crop.
Yields, Fruit Thinning and Harvesting Mature trees of large fruited cultivars should be limited to 175 to 250 fruit. It is common, however, for these trees to mature 350 to 600 fruit. Heavy fruiting and seed formation will effect cropping the next year, vegetative growth, tree health, fruit size and ability to handle freeze damage. Less vigorous cultivars will have sufficient crop loads with 75 to 150 fruit. Small fruited vigorous cultivars are capable of handling crop loads of 350 fruit or more. To grow the best quality fruit and to regulate crop loads for optimum tree performance, thinning the fruit on a persimmon tree is often necessary. Persimmons have a tendency toward biennial bearing with large crops of small fruit one year and light crops of large fruit the next. Mature trees, especially when grown under non-improved conditions, regulate themselves, but overall yields are low. Growing conditions with increased fertility and pest control improve yields, but may lead to over-cropping and alternate bearing tendencies. Excessive cropping can be regulated by cutting fruiting twigs and thinning newly set fruit.
Most flowers are developed from the last few buds on a twig. Pruning out some of the less vigorous or inside growing fruiting twigs during late winter will reduce fruit formation in the spring. Shoots and twigs that are shaded by the canopy or are weak-growing can be removed.
Hand thinning of fruit is done after the post bloom drop or about 3 weeks past flowering. One to 4 fruit are left on a shoot. These should be spaced about 6 inches apart. Fruit should not touch each other when mature, since this provides a spot for the buildup of pests and produces scarred, sub-quality fruit. The first fruit toward the base of the shoot is generally the largest and best developed. It should be left and those that are small or misshaped should be removed. Selecting fruit with a large well-developed calyx is important, because these fruit will have less chance for calyx-separations. The amount of thinning should be determined from the tree's performance during previous years. Both heavy cropping and early defoliation the year before will encourage a light bloom the following year. Thinning should be limited in a year with a light fruit set. Under good growing conditions and/or pollination, thinning is important for maximizing quality annual yields.
Thinning fruit is more important on some cultivars than on other ones. `Fuyu' and `Matsumoto Wase Fuyu' tend to set excessive crops of clustered fruit. `Ichikikei Jiro', `Jiro', and `Izu' regulate crop loads better so heavy thinning may not be necessary. `Tanenashi' will overproduce and this sometimes limits tree size. Experience is often necessary to determine the amount of thinning and this can only be gained after 2 or 3 years of cropping.
Harvesting Persimmons ripen from August through December. Non-astringent fruit are picked when color has developed to the yellow/orange/red stage and most or all of the green is eliminated. Astringent fruit are picked when soft or just before softening occurs.
Soft fruit can be clipped at the stem as pulling will often leave the calyx and some of the fruit on the tree. Firm fruit can be pulled if the proper technique is followed. The fruit are grasped and twisted to ½ turn, then pulled off in the same direction the twig they are attached to is growing. This will break the stem leaving the calyx with the fruit and will prevent breaking the limb or twig of the tree.
Bud Break and Freeze Damage Bud break in oriental persimmons generally occurs late. Usually it is one month after apples, peaches, pears, blueberries and bunch grapes and two weeks before native persimmon, pecans and muscadine grapes. Since oriental persimmons are propagated on heterozygosis native trees bud break time among many trees of the same cultivar will vary.
Freeze damage usually occurs after buds swell and growth activity begins. This normally occurs February, March or April when frost or freezing temperatures follow a warm spell. Autumn and mid-winter non-dormant trees that are actively growing could also be damaged during freezing periods; however, these conditions are rare. In the fall, trees become dormant, loosing their leaves through natural senescence, leaf spot defoliation and/or frost. Lower winter temperatures occur and trees accumulate chilling units. It is not certain how much winter chilling is necessary for persimmons, but even with small amounts trees will break dormancy and grow satisfactorily. When long periods of warm weather occur after a dormant period, trees will initiate growth. Heat unit accumulation is a major factor in stimulating growth activity after dormancy. In January and February, generally 6 weeks of warm days without freezing temperatures are needed for bud swell. In late March and April only 1½ to 3 weeks are necessary for activity to occur.
If freezing temperatures occur after budswell, new leaves, shoots, swelling buds, and small twigs can be killed. If low temperatures are prolonged or severe they will cause damage to large limbs and trunks. Young healthy trees that are in the bud swell stage will usually recover from a brief period of 20°F. After a severe freeze the green cambium layer may change to brown and appear water soaked. If the terminal buds are killed, growth and sometimes flowering will occur from dormant lateral buds. Older and/or weaker trees or those that have already formed leaves will experience greater degrees of damage. Limbs, trunk portions, and entire trees may be killed. Growth, if it occurs, will come from adventitious buds on the trunk or latent buds in the limb axis. Trees may die or major damage may require 2 to 3 years for recovery. Weakened trees can be subject to fungi infecting the injured tissue and spreading to other sections of the tree. Tree borers may be associated with these injured sites.
Freeze damage may be lessened by choosing hilltops or areas with good air drainage. Cold pockets and low-lying areas should be avoided. Healthy trees are less susceptible to cold injury. Factors that cause tree stress such as over-production, inadequate nutrient levels or early autumn defoliation should be avoided. Painting trunks with white interior latex paint may prevent sunscald freeze damage, which occurs most commonly on the southeast side of the tree. When warmed by the sun, this portion of the trunk becomes active and is then frozen. Overhead irrigation of ¼ inch per hour during calm conditions and temperatures between 24 to 32°F will ice the trees and protect them from wood damage.
Placing the graft union slightly below the ground or covering it with mulch or soil will allow the tree to sprout from undamaged scion portions. Young trees will rapidly reestablish from a new sprout. It is likely that during a 10-year period, trees in the central and northern areas of the state will suffer some freeze damage.
Insect Pests Scale Insects: Of the insects that are associated with persimmons, those that attack the tree are more serious than those that affect the fruit. The most devastating insects are the scales found on the bark, and white peach scale is the most common. Infestations become highly visible when the males emerge in warm weather and cause a snowy-white appearance on limbs or trunks. If a scale insect is present, lightly slicing into the green cambial layer with a knife will reveal reddish-purple dots where it has probed and is feeding on the tree.
Scale insects can be scraped off with a knife, especially when colonies are small. If spring, summer, or fall buildup of scale occurs, an insecticide may be applied to the insects because they are somewhat mobile in warm weather. Severely infected limbs should be pruned out. A 3% dormant oil spray can be applied at, or just before, bud break in the spring. Since oil will cause increased tree temperatures and speed up leafing, the application should be late to guard against increasing chances of freeze damage.
Persimmon Psylla The persimmon psylla is an insect which feeds on leaves. Small, black-bodied adult flies with large, transparent wings can be seen feeding on the upper leaf surface beginning at flowering and on through spring and summer. They attack tender foliage of D. kaki as well as D. virginiana. Older trees are not plagued by psylla, perhaps because they have less succulent growth. Generally, psylla are detrimental to establishment of young trees. Killing the flies during the bloom period will prevent successive generations and population buildup.
The female psylla lay eggs at the margin of the underside of the leaf. When the nymphs hatch they feed and inject toxins which cause the leaf to curl around them, making control difficult. Mealy bugs are also associated with the psylla nymphs in the curled leaf. Ants will feed on the honey dew or sweet excrement which is produced by the insects. Shoot stunting will result causing low yearly growth in young trees. Both the psyllid and scale insects are generally controlled by an insecticide in combination with a fungicidal cover spray at full bloom and 3 to 4 weeks later.
Tree Borers Various moth and beetle larvae have been observed feeding on trees. They enter through wood left from exposed pruning cuts, dead limb stubs, cracking bark at crotch joints or other injured areas on the tree. Wood may be first softened or weakened by fungal infections or freeze damage. The larvae feed just under the bark boring out tunnels and filling them with a brown frass. More than one larva are usually found in infection sites. Flat-headed, wood-boring beetle larvae are common and appear to colonize wounds in July. Moth and other beetle larvae are found at different times. Vaporous insecticides which control borers are not labeled for persimmons.
A white roundish worm occasionally bores into small trees at soil level during late August and September. Proceeding downward into the soft root tissue, the insect pushes behind sawdust and excrement. Because they feed on live tissue, a gummy sap is secreted by the tree and combines with the insect's waste to fill the tunnels. This oozing, gummy substance can be seen on the tree at the tunnel entrance. The worm feeds on the root tissue during winter, burrowing out a long tunnel and escaping in the soil. Vaporous insecticides are used by nurseries in early August to control this pest when it becomes a problem.
Fruit Insects Of the insects associated with the fruit, stink bugs are the most significant. They are only a problem on non-astringent types and feed as the fruit colors in September through November. Damage will show up as off-white sections in the fruit just under the peel and are subject to decay. Various species of thrips can be seen on the flowers and around the newly developing fruit. They may increase early fruit drop and cause some fruit disfiguration. Although they are a significant pest in Japan, their impact here is not known.
Diseases
Leaf and Fruit Spots A significant fungal pathogen limiting performance is Cercospora spp. leaf spot. It contributes to defoliation which starts in late August as the fruit begin to ripen and continues through September and October. Problems related to defoliation include cessation of fruit sugar accumulations and fruit ripening, biennial bearing tendencies with low overall yields, and increased susceptibility to freeze damage. Control can be obtained by applying a fungicide cover spray during full bloom and again 3 to 4 weeks later. Cercospora inoculation appears to begin at shoot expansion, leaf formation, and flowering.
Starting in late August and continuing until the leaves abscise in October, November, and December, various other fungal species are associated with spots which form on the leaves and fruit. Alternaria sp., Gloeosporium spp. and Phyllosticta sp. are three aggressive pathogens. Anthracnose or bitter rot, Gloeosporium spp., infects fruits, shoots and twigs in both Japan and Florida. `Fuyu' and `Izu' are susceptible, but some cultivars have resistance. Colletotrichum sp. has been detected on ripening fruit and Ramularia sp. has been found on leaves in early June.
Infections of these diseases become readily noticeable during late summer and fall. Inoculation times are earlier and cover sprays during mid-August to mid-October will improve leaf retention and decrease fruit lesions. Late summer sprays to control leaf spots will improve leaf retention and tree health, but are less important than the bloom and post-bloom sprays. Some cultivars have specific resistance to some pathogens. Two other diseases are reported in Japan; Botrytis cinerea causes brown leaf patches, and bacterial blast (Pseudomonas syringae pv. syringae) causes leaf spots and blackening of the stem and leaf petiole.
Wilt and Canker Diseases
With the introduction of the oriental persimmon into this country came the wilt disease Cepehalosporium diospyri. D. kaki and D. lotus are immune to this pathogen, but the native D. virginiana had no resistance. Large trees throughout the south have been killed because of infections. Areas where root sprouts sucker up near dead trees and grow for a few years before dying are known to occur from disease infections.
If oriental cultivars propagated on D. virginiana are carrying the disease, the pathogen will move through the D. kaki to the rootstock and kill the tree. Wilting and death of the top are the visual symptoms. Occurrences of the problem are not common, but if infected native trees are near the planting site the potential exists for devastating infections.
The most likely method of cepehalosporium transmission is the twig girdler. The female visits various tree species, piercing the bark below buds of the terminal twigs to deposit an egg. After laying her last egg, she girdles the limb, which soon snaps off and falls to the ground. Egg laying occurs in the fall, generally in September and October. Insecticides with the late fungicide applications may be a method of control. Girdled limbs should be removed from the orchard and burned to limit next year's population buildup. Scouting for the pest during the fall and pruning back from her cut may also be important. The twig girdler frequents a variety of hardwood trees including hickory and pecan.
Other disease symptoms can sometimes be observed on persimmons. Occasionally, a tree will have small leaves and fruit with leafless terminal twigs, and die back of these shoots. The disease Phomopsis spp. has been associated with these problems, although this may not be the only cause. Phomopsis spp. has also been associated with the wilting and subsequent death of shoots as they grow during the spring. Cracking of the bark at limb joints is another disease symptom, and may relate to rapid growth and high nutrient levels. Verticillium albo-atrum, and Botryospharia dothidea have been reported to infect persimmons and may be associated with any of these problems. Budding trees with infected scion wood may transmit the symptoms. Pruning an infected tree and then a healthy one, without sterilizing the tool, appears to spread the disease.
ACKNOWLEDGEMENTS
Appreciation is extended to Wayne Sherman, Howard Miller, Tim Schubert, Ralph Sharpe, Jim Mercer, Paul Lyrene, Frank Kaufman, Bob Wallace, Robert Dunstan, Richard Harrison, Jack Hamilton, Peter Andersen, Linda Baker, Ron Lambert, Chris Thomas and Joyce Ahrens for their assistance.
See you Monday night, October 15!
Tropical Fruit Club
P. O. Box 37