Emerald Ash Borer a Threat to All Ash Trees

Spread of Emerald Ash Borer puts area ash trees at risk

Bill Sevier: Ask a Master Gardener

Saturday, October 29, 2016

Q: My friends in Michigan say they are losing their ash trees to an insect. Is my tree at risk here in Tulsa? Jim, Tulsa.

A: Your ash tree is not at risk yet but may very well be in the near future due to an insect called the Emerald Ash Borer.

This insect, like so many of the insects and diseases that have devastated trees in the U.S., is an import from Asia. This has the same potential for destruction of all varieties of our ash trees, as did the imported diseases that killed our elms and American chestnuts.

The Emerald Ash Borer was first seen near Detroit in 2002 and has been noted to spread initially eastward then onto states south and west. Until recently, it had been found in all surrounding states but not in Oklahoma. Recently, it has been reported in the northeastern part of the state and can only be expected to spread. The borer often is transported to new areas by firewood and nursery stock.

The insect is said to cause the death of many millions of ashes in the heavily involved states, and that potential exists for all our ash trees.

The borer adults are metallic green and about ½-inch long. The adults do little damage, but their larva bore into the outer layer of ash trees, where they feed and slowly block the circulation of the tree. Trees initially experience dieback of the uppermost part of the canopy, which spreads to involve the whole tree. Trees often have stress-induced secondary shoot growth on trunks and at the tree’s base.

Studies looking at ways to prevent infestation and to treat those trees already involved have shown there are effective controls, but they are most effective when used for prevention. Trees with borers may benefit from treatment at early stages of involvement, but most likely those trees with dead tops will die over the next few years.

The effective insecticides are all “systemic,” which means they must enter the tree’s circulation. This is done as a soil drench over the root zones; by injection directly into the tree, or spraying directly on the tree’s trunk. Injections must be done by an arborist, but drench and trunk spraying can be done by homeowners.

The big question involves which trees to protect and when to do it. Treatments are expensive, time consuming and add insecticides to the environment. This should only be done with forethought.

Currently, trees should be considered for treatment if the borer has been found in other trees within 10-15 miles. That is not the case as yet in Tulsa but likely will be in the future.

More information about the Emerald Ash Borer and preventative measures may be found on the website of The Emerald Ash Borer Information Network at emeraldashborer.info. Also look at the Oklahoma Forestry website for description of signs of the insect’s tree involvement.

Be aware that the OSU Extension Offices in Oklahoma will keep track of the spread of the beetle and publish information as to the locations.

Garden tips

§  Keep leaves off of newly seeded fescue to prevent damage to the sprouts. Also, the soil of newly seeded fescue should be kept moist until the sprouts are about 2 inches, then water less often and for longer times to encourage deep root growth of the seedlings.

§  Remove vegetable garden debris to prevent many garden pests and diseases from overwintering in these materials.

§  Plant cool-season cover crops like Austrian winter peas, wheat, clover and rye in otherwise fallow garden plots.

§  Cover water gardens with netting to keep out falling leaves.

Dividing Perennials in Fall

Perennials give clues when its time to divide, replant

Brian Jervis: Ask a Master Gardener

Saturday, October 22, 2016

Q: When should I divide my pampas grass? What about my iris? G.W., Tulsa

A: Pampas grass is a perennial, a class of plants in which the tops die back in winter but re-emerge from roots in spring. A general rule of thumb for dividing and replanting perennials is that it depends on the time of blooming. For those blooming in spring, fall division may be best, and for those blooming in summer and fall, divide in spring (or after fall blooming is completed).

There are many types of perennials, and not all fit into the above recommendations about when to divide. Some do best not divided at all, unless new plants are needed.

Perennials will often give you clues as to when they need dividing. With increase in density of the root system, the center of the root ball often dies so the plant may have little or no growth in its center. Also with crowding of the roots, the whole plant simply doesn’t perform as well, with substantially less growth and numbers of blooms. Another reason to divide is if the plant has simply outgrown its space.

As to when to divide Pampas grass, it seems to do best divided in the early spring after the dead foliage has been cut back to a height of 6 inches or so. Like many other perennials, the whole root ball can be dug up and cut into pieces or sections of the roots removed while the remainder stays in place. In any case, many of the grasses, and especially Pampas grass, have extremely tough root balls and an ax will usually be needed to divide.

Perennials like black-eyed Susans, purple coneflowers, monarda and yarrow can be divided in either spring or fall, while asters, blanket flower, bleeding hearts, cannas and chrysanthemums do best if divided only in spring. Iris do best if divided at least a month after they complete spring blooming.

Plants that often need no division, unless new plants are needed, are hostas and peonies. Peonies are a little difficult to divide and replant in the sense that they must be replanted at the proper depth and, in some cases, may take 1-3 years before beginning to bloom again. Peonies should be dug up and divided in September or October.

When dividing, plan ahead. Water the plant and dig its new hole, if moving it, beforehand. Adding organic compost to the native soil at replanting is beneficial in all types of soils. When transplanting, take care to not let roots dry out; a cloudy day is best.

A benefit of dividing plants, other than improving their health, is that you will end up with several new plants to share with friends and neighbors.

For more information as to the time to divide and how to do it, consider going to the Clemson University Extension website and search for “dividing perennials.”

Garden tips

• ·       Plant container-grown trees and shrubs this month. Fall is generally the best time to plant. At this time, the plants have no energy drain to produce leaves and can concentrate on growing a root system until the soil gets cool in winter. They are better prepared for spring growth if planted in the previous fall.
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• ·       Check and treat houseplants for insect pests before bringing inside. Look at the roots and repot those that are rootbound. Irrigate the soil thoroughly before bringing inside. Spray with horticultural soaps or oils if there is evidence of insects.
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• ·       There is still time to plant radishes and mustard in the fall garden.
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Planting Azaleas in the Fall

Azaleas can be planted in fall or spring

Bill Sevier: Ask a Master Gardener

Saturday, October 15, 2016

Q: What time of the year is it best to plant azaleas? How best to plant them? K.D., Tulsa

A: Ideally, azaleas should be planted either in early spring or in fall after it cools. Either time is acceptable.

When planting in fall, it is suggested that you delay mulching until after the first frost so the plants will be assured of developing dormancy for winter.

Azaleas have some cultural needs that are a bit different from many other shrubs, at all times of the year. The chief difference is that they need an acidic soil, with a preferred pH (measure of acidity) in the 4.5 to 5.5 range. Our native soils do not normally have this degree of acidity, so some adjustments are usually needed.

To determine soil acidity, along with information about the nutrients nitrogen, phosphorus and potassium, have a soil test performed before planting. Instructions on how to perform a soil test and also how to plant azaleas may be found on the Master Gardener website.

If more acidity is needed, there are two options. The best option is to mix peat moss 1:1 or 1:2 with native soil. Peat moss is acidic and will usually produce an adequate pH. Another way to add acidity is to use elemental sulfur (pure sulfur) and mix it into the soil. The amount of sulfur to add depends on the pH, but a safe amount to use would be 7 tablespoons for every 10 square feet of soil. Sulfur will not immediately lower pH; it takes a few months for this to occur.

Azaleas have fine, shallow net-like roots. To plant them, create a blunt cone of soil, spread the roots out over the cone like an umbrella and cover with several inches of soil.

In well-drained soils, plant azaleas at the same level as they grew at the nursery — never deeper. If your soil is heavy clay, as it often is, it is best to plant above ground in a large mound of prepared soil. Spread the roots out and plant them on top of the mound, with a few inches of soil for cover.

In both cases, they should receive generous amounts of loose mulch at the time of planting and yearly thereafter. There is no best mulch. Any mulch that is loose is useful. Contrary to popular belief, there is no mulch that will add acidity to the soil.

All the plants need generous irrigation during establishment and subsequently in all seasons.

A slow-release fertilizer, such as Osmocote, may be mixed with the soil at the time of planting and, if so, no further fertilizer will be needed the rest of the following growing season. Azaleas, in general, need less fertilizer than other shrubs and will suffer if excessively fertilized. If mulched yearly, adequate nutrients may be supplied by the decaying mulch.

Garden tips

• Peonies, daylilies and other spring-flowering perennials should be divided or planted now.

• Dig and store tender perennials like dahlias and caladiums in a cool, dry location. Cannas and elephant ears can also be dug, but most will survive the winter fine if mulched heavily and in a sheltered area.

• Plant fall mums and asters, and keep them watered during dry conditions. Don’t crowd because they take a couple of years to reach maturity.

• As leaves begin to drop, keep them off any newly seeded fescue lawns

Fall is the Best time of the Year to Plant Trees, Shrubs and Perennials

Fall is good time to plant trees

Brian Jervis:  Ask a Master Gardener

Saturday, October 8, 2016 12:00 am

Q: Is it best to plant trees in the spring or fall? B.F., Tulsa

A: The question brings to mind the adage, “The best time to plant a tree was 20 years ago. The second best time is now.” — Chinese Proverb

The short answer is that fall is an excellent time to plant trees; but spring and fall are acceptable times of the year to install trees, shrubs and perennials. There are some exceptions, however, depending on the plant type.

An appeal of fall planting is that many gardeners are enthusiastic about returning to the garden following the heat of summer. In addition, one is likely to find some bargains in the nursery stock in fall.

The advantages of fall planting is that trees are entering dormancy and no longer expend energy on making new leaves. This means that most of the plant’s energy can be directed toward growing a root system, in preparation for next year’s growing season. The soil usually remains warm enough for roots to grow well into winter.

Due to high demands and a limited root system, plants installed in spring or during summer may experience water loss from leaves that exceeds the plant’s ability to deliver. In spring, all newly-planted trees need careful irrigation and mulching.

Fall planting gives trees a head start. OSU performed a study comparing a variety of 2-year-old trees that were planted in spring and fall. They found trees planted in fall had up to 50 percent larger root balls and trunk thickness when compared with spring-planted trees after one growing season. This advantage applies not only to trees, but also to shrubs and ornamentals.

However, most bare-root plants should not be planted in fall but in spring between mid-February and mid-April or up to the end of the frost period. They must grow tiny rootlets to absorb water, and this happens as buds begin to swell in spring. Other than seedling-sized evergreens, only deciduous plants can be transplanted with bare roots, and then only when dormant or leafless.

Another exception to fall planting are evergreen shrubs. These shrubs will continue to lose water in winter, and the demand may exceed the root’s ability to deliver. If they are planted in the fall, they must be watered frequently, sheltered from wind and have a thick layer of mulch.

An additional concern about fall planting relates to crape myrtles. Carl Whitcomb, a retired OSU professor and expert on crape myrtles, recommends they be planted in June through early September and not after October. They need warm soils to grow water-absorbing roots, and the cool soils of winter prevent the development of these roots.

For more information about tree planting, obtain the OSU fact sheet “Planting Trees and Shrubs” online. This fact sheet has the what, when and how to plant trees in all types of soil. Also see Whitcomb’s book, “Establishment and Maintenance of Landscape Plants,” for additional authoritative information.

Garden tips

§  Plant cool-season annuals like pansies, ornamental cabbage or kale, snapdragons and dusty miller when temperatures begin to cool.

§  Prune trees or shrubs anytime there are dead or diseased limbs. Do not perform routine pruning now. Pruning before winter dormancy may stimulate new growth sensitive to the cold. Fall pruning also removes energy stores needed for winter survival.

§  For summer-blooming shrubs, prune in late winter before spring growth starts, and prune spring-blooming plants, such as azaleas, after blooming is completed.

§  Continue to replant or establish cool-season lawns like fescue. Mow and neatly edge warm-season grasses before the first killing frost.

Pine Wilt Disease is Fatal

Disease affects pine trees

By Bill Sevier Ask a Master Gardener | Posted:

Saturday, October 1, 2016 12:00 am

Q: My Austrian pine has started turning brown. It involves most of the tree. I don’t see anything abnormal other than brown needles. What should I do? Doris, Tulsa.

A: Unfortunately, the most common cause of pine trees turning brown and dying in the latter part of summer and fall is a condition called “Pine Wilt Disease.”

This condition is due to an infection of the tree’s circulation with a microscopic worm called a nematode. This infection is spread from tree to tree by an insect, the pine sawyer beetle. Because this infection is native born, native trees, such as loblollies, are less susceptible than the imported ones like the Austrian pines.

This beetle becomes infected by feeding on trees containing the nematode. The nematodes do not harm the beetle, but the infection is spread when it feeds on a healthy tree. The nematodes build up in the infected tree until they block all the circulation. The limbs become brittle and have little sap or resin. The needles stay fixed to the tree (as opposed to other conditions in which they drop) and the tree dies. Often there is an associated fungus that stains the wood of the tree blue. If a limb is cut, in addition to the lack of sap, bands of blue discoloration may be seen.

This is a fatal disease. The tree should promptly be removed and either chipped, burned or sent to the landfill. It is infectious, and if left in place, will infect a new crop of pine sawyer beetles the following spring that then spread the disease.

The other significant causes for browning of pine needles occur at certain times of the year. In spring, a disease called “Tip Blight” or Sphaeropsis or diplodia, appears as stunting and die-back of new needles (candles) on the tips of lower limbs. There may be dried resin and pepper-like specks on needles and cones. Also in spring, the pine tip moth may attack the new growth on tips of limbs, producing hollowed out limbs and webbing. These conditions involve only the tips, sparing the rest of the limb.

Another cause for brown needles is winter damage due to low temperatures and drying winds. This is often one-sided and is noted in early spring.

In late summer, another fungal disease called Dothistroma Needle Blight may appear, involving the tips of lower limbs. It may spread inward. The needles have discolored bands and die during the winter. The tree sheds them the following spring and summer.

Lastly, one of the more common causes, and one the Master Gardeners are often called about, is “normal needle drop.” Pines shed needles in the fall similarly to deciduous trees shedding their leaves. This involves the older needles, the ones closer to the trees trunk.

For the problems with pines other than pine wilt disease, there is treatment. Contact the Master Gardeners office for recommendations for control of the fungal and insect issues.

Garden tips

Begin preparing your outdoor plants for a move indoors. Move houseplants indoors when the outside and indoor temperatures are about the same. For plants in full sun, move to shade. Begin with light and then heavier shade over a week’s time to prepare the plant for the low light indoors. If you move the plant from full sun to a low light indoor situation, the plant may experience “shock,” lose leaves and perform poorly inside.

Inspect plants for insects and disease and treat accordingly. In many cases, a few insects can be controlled by hosing down the plant and removing them by hand. Another option is to use an insecticidal soap spray. This is effective and safe for you and your plant.

Also consider drenching the pot with 2-3 pot volumes of water to help remove insects and residual fertilizer salts.