The next meeting will be Septmeber 18th at the regular time (1:00 p.m.). Come early and fellowship with other master garderners.Mark's latest article  "DESTRUCTIVE EMERALD ASH BORER" from today's Bulletin

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     GARDENING HORTICULTURE NEWSLETTER

 

May 2008

 

 

 

FLOODING ENDANGERS TREES

          For certain Arkansas tree species, just a few hours of flooding can prove fatal.  Even after five hours of standing in a couple inches of water, trees start shutting down photosynthesis.  Trees that can’t tolerate flooding include hickories, southern red oak, dogwoods, shortleaf pines and eastern redbuds.  Spring is a time when trees are especially vulnerable.  This is their big time when they are expending a lot of energy blooming and putting out leaves.  The key problem is that the flooding rapidly depletes the oxygen in the soil.  They have to have oxygen in the soil for root respiration. 

 

When the oxygen is shut out, anerobic processes begin. The foul smell is the first clue the process has started. That
produces toxins in the soil and the absorbing roots begin to die. Everything shuts down.
Some species handle the water better. They’re adapted to the flooding. They’ve evolved in wet ecosystems.

These include cypress, willows, sweet gums, green ash and maples. Other species that are somewhat tolerant of flooding include some hackberries, oaks, loblolly pines, birches and elms.
Some trees can tolerate 30 to 80 days of root submergence. In addition to species, how the tree copes with the water depends on age, health and how leaved out the trees are.


The most critical time is just after the leaves have fully expended. That’s when the most potentially dangerous flood damage can occur.


Early signs of damage include brown, wilted leaves and branch die-back. The injuries may leave the trees susceptible to insects and disease. It could take years for some of them to die.
Unfortunately, there’s not much people can do to help their flooded trees.

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SMALL CRITTERS POSE BIG PROBLEMS FOR HOMEOWNERS
For some gardeners, moles can make a mountain out of a …mole hill. These little critters – moles – are just 4-9 inches long, but their underground tunneling makes them one of the most destructive mammals that can inhabit a front yard.


Their digging activities aerate the soil and they eat invertebrates – like earthworms and grubs – but their digging often damages roots and bulbs, and the volcano-like mounds of dirt they leave behind can make a lawn downright unsightly.


Gophers can also wreak havoc in lawns and gardens. They range from 3-10 inches, and their mounds are crescent-shaped rather than circular like those created by moles. They mainly eat plant material.


Raised earth and ground that sinks beneath your feet are telltale signs that one of these burrowing pests are on site. To control the problem, you must figure out which pest is present.
Moles follow their food source. When the ground is dry, they burrow deep to find grubs and earthworms; when the ground is warm and moist, they inhabit the subsurface tunnels that can be easily detected by property owners.


When we water and fertilize our lawns, we create really good habitat for earthworms and grubs – and really good habitat for moles. Moles don’t always leave mounds on Arkansas property, possibly because of the texture of the soil.


Dying or vanishing shrubs and plants may be the fault of gophers.
There are several folk remedies for ridding property of moles, such as using chewing gum as bait to cause digestive blockages leading to death, but they simply don’t work.


Poison baits are available in stores, but are illegal to use under Arkansas Game and Fish regulations. Plus, moles don’t eat grain, which is used in many poisons. Fumigants, too, are illegal, and even if they weren’t, they don’t typically work. Moles are accustomed to living in areas with little oxygen, and the fumes don’t stay trapped under the ground but rather escape through the coarse dirt.


Some companies market mole repellents, but the effectiveness of those is questionable.
It’s not really clear whether repellents work. Perhaps the moles’ food source dries up or they move somewhere else for another reason. They’re difficult to study because of their underground habits.
Traps are the most reliable way to deal with moles, and two of the most popular types of traps available are a harpoon trap and a scissor trap.

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The harpoon trap is probably the easiest to use and is available at most farm, hardware and garden stores. The scissor trap requires some excavation of the tunnel, and repacking of the soil over the trap’s trigger.
For more information on mole control, stop by the Cooperative Extension office and pick up “Controlling the Eastern Mole” factsheet or go to our website, www.uaex.edu.

DOGWOOD
Dogwood borers, Synanthedon scitula, are pests of dogwood, pecan, hickory, elm and willow. The damage is done by the larvae feeding under the bark. An early symptom of borer damage is leaves turning prematurely red in the summer. Swollen areas on limbs, peeling bark, and exit holes are additional symptoms. Heavily infested limbs and branches can die. Successive seasons of infestation may kill the tree entirely. Most dogwood borers emerge in May, but a few continue to emerge until September. The larvae overwinter in the tree. The best defense against borers is to maintain good tree health. Dogwoods grow best in humus rich soil with good drainage and afternoon shade. Borer sprays may be applied to the trunk in May. The treatment should be repeated at 6-week intervals 2-3 times. Bifenthrin and permethrins are labeled for borer control. A fine wire inserted into the entry hole will sometimes kill the larvae.

HOSTA
Hosta samples have been arriving at the plant disease clinic in Lonoke with Hosta Virus X. This is a sap transmitted virus, and like all viruses is not curable. The virus comes into a nursery from producer fields. This is largely due to machine harvesting and bulk washing to prepare for shipping. At the nursery or the homeowners, it is spread by trimming or dividing infected plants. The virus is not spread by insects nor is it soil borne. To prevent virus transmission, great care must be taken to dip tools in a 10% bleach solution before handling another Hosta. Wearing disposable gloves and changing them between plants is also advisable. Symptoms are blue or yellow ring spots, mottling, bleeding along veins, and/or a zipper pattern. The bleeding along the veins is often blue in color. This virus seldom kills a plant, but weakens them and often causes unsightly necrotic spots on the leaves as well as the mottling. The clinic has a reliable Elisa test to detect the virus.

MAGNOLIA
Lichenized algal leaf spot is caused by parasitic algae that cause twig cankers and leaf spots. Southern Magnolia (Magnolia grandiflora) is susceptible to infection when hot humid weather provides optimum conditions for the growth and spread of


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this pathogen. Lesions begin as round, green, somewhat velvety colonies on leaf surfaces or twigs. On leaves, the spots eventually turn reddish-brown with age. Algal leaf spot that has been colonized by fungi take on a grayish appearance and are called Lichenized algal leaf spot. The disease is most severe on Magnolias that are weak and in poor health. Trees that are grown in full sun and subjected to high temperatures and excessive leaf wetness are more severely affected. Cultural practices to minimize disease include a proper water and fertilization schedule. A soil sample should be taken to rule out nutritional and pH issues. Irrigation methods that spray water on the leaves should be avoided. All fallen leaves and twigs should be raked up and destroyed. Pruning overhanging branches from surrounding plants will improve air circulation. Lastly, applications of copper fungicides (Kocide) every 2 weeks during wet weather have proven helpful.

ARKANSAS FRUIT VARIETIES IN DEMAND WORLDWIDE
(Howell Medders, University of Arkansas)
“Just a bunch of briars, but some sophisticated ones at that,” John R. Clark likes to say about the blackberry varieties developed in the breeding program he directs for the University of Arkansas System’s Division of Agriculture. But these briars have pedigrees and are in demand around the globe, which has led to partnerships between the Arkansas breeding program and companies in Chile and England, with more to come.


A horticulture professor based on the university’s Fayetteville campus, Clark inherited in 1997 a unique collection of blackberry germplasm and continues to improve it in a fruit breeding program that also includes grapes, peaches, nectarines and blueberries. His predecessor, Distinguished Professor Emeritus James N. Moore, started the collection in 1964.


Moore started patenting UA varieties with the Reliance grape in the early 1980s and Clark has continued to do so. Royalties for the propagation of plants are paid to the university.
Clark says he realized that, while the germplasm collection exists to benefit Arkansas fruit growers, “we couldn’t keep it to ourselves if we wanted to.” Protecting a plant worldwide with plant breeders’ rights available in over 60 countries and strictly enforcing this protection is difficult, he says. Others can legally use patented varieties for breeding with no return to the university.


“Our testing of Arkansas breeding lines and varieties in other states and countries revealed opportunities to maximize genotype by environment interactions,” Clark says. “Some of our germplasm that doesn’t do well in the heat and humidity of our summer does great in a more moderate climate.” Clark recognized that there were lines in the program – also in the grape, blueberry, peach and nectarine breeding programs – that likely would be discarded in Arkansas but might have use in other locations.

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So, starting about 2002, Clark began broadened testing and breeding relationships with partners in various locations such as South America, Australia and South Africa in the southern hemisphere, where the growing season occurs during Arkansas’ winter, and the United Kingdom, where fresh fruit is not likely to be produced and marketed in competition with Arkansas producers.
The partnerships were developed to strengthen the program on behalf of Arkansas growers by generating royalty income for research, Clark says.


One partner is Hortifrut, one of the world’s largest fruit growing and marketing companies based in Santiago, Chile. Another is Hargreaves Plants, a nursery company in Spalding, Lincolnshire, United Kingdom.


“Our partners pay for access to our material for us in the cooperative improvement programs, and if a variety is developed that is commercialized the university receives royalties,” Clark says.
Other partners are interested in simply growing already patented Arkansas varieties of blackberries, grapes, peaches, nectarines and blueberries. One of these is Eurafruit, which is testing Arkansas varieties on its farms in South Africa for production and shipment of fruit to Europe. Ozeki Nursery in Japan is licensed to propagate and market a variety of Arkansas blackberry plants.


“Blackberries are hot, right now,” Clark says, “and fortunately, for our purposes, it is mainly a fresh market crop with limited storage time compared to frozen berried.” However, he adds, Arkansas growers could benefit from an expanded “market presence” over a longer period of time to strengthen consumer demand for blackberries if berries from other areas find their way into local stores.


Come June, Clark says, the deal-making goes on hold while he attends to his main chore of tasting berries and evaluating plants from this year’s almost nine miles of seedlings at the Division of Agriculture’s Fruit Research Station on Red Lick Mountain near Clarksville. He’ll select plants for further crossbreeding and maybe one or two from advanced lines for consideration as new, patented varieties.


The Arkansas breeding program has produced some of the world’s most widely planted blackberry varieties, including several that are thornless, and planting is on the increase in the U.S. and other countries. Unlike the wild blackberry briars, the Arkansas varieties have erect canes rather than vines and are easier to manage. Named for Native American tribes, the most popular are Navaho and Ouachita.


The program achieved a major breakthrough in the late 1990s when the first “primocane fruiting” types were selected. Primocanes are first-year canes that normally don’t bear fruit. Blackberries normally are borne only on second-year canes. Thus, only about half of the canes on each plant produce berries. This new type of plant can provide options for growers in time of ripening and management of plantings, Clark says.


Primocane-fruiting raspberries became commercially important about 25 years ago. They produce high-quality berries on plants that can be managed for production for longer periods, particularly into the fall season, Clark says.


The Division of Agriculture has released two primocane varieties, “PrimeJim”® and “PrimeJan”®, named for James Moore and his wife. But they are not well adapted to Arkansas conditions, Clark says. He sees potential to license the primocane fruiting material to other breeding cooperators to help generate funding for research to combine primocane fruiting with other traits needed for Arkansas growing conditions.


“Science works best when scientists share information,” Clark says. Hybrid seedlings grown in Chile or England, for example, might generate a primocane fruiting plant that would be perfect for those locations or for Arkansas, he says.
 

If you have questions regarding any of the above topics, please feel free to contact me at the University of Arkansas Division of Agriculture Baxter County Extension office at 425-2335.

Sincerely,

Mark D. Keaton,
County Extension Agent-
Staff Chair
 

 

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