Hort Update for February 18, 2020

Hort Update for February 18, 2020, Nebraska Extension, http://communityenvironment.unl.edu/update02182020
Serious ConcernsMajor Symptom:
1. Oystershell scale Check now for evidence of last year's insects
Minor Issues
2. Winter desiccation Be alert in western Nebraska; probably not an issue for eastern parts of the state
3. Brown marmorated stink bug Warm days result in active insects; stink bugs become an indoor nuisance
In The News
4. Spotted lanternfly Has not been found in Nebraska yet; report possible sightings
Timely Topics  
5. Magnolia scale Scout plants with a history of infestation
6. Bagworm Encourage client's to remove last year's bags from high value small trees
7. Pruning trees & shrubs Good pruning practices - timing and techniques - essential for plant health & productivity
8. Fruit tree pruning Time pruning on tree species



1. Oystershell scaleCheck now for evidence of last year's insects

The dormant season is a good time to check plants for oystershell scale. If found, make plans for scale management. Oytershell scale can be found on many shrubs and trees with lilac, cotoneaster, and dogwood being common hosts in Nebraska.

Scale insects are easy to overlook because they’re small and immobile most of their lives and do not resemble a typical insect. They attach themselves to twigs, grow a protective covering and can appear to be part of a branch to the untrained eye. Scale insects can build up to large infestations with branches dying before they are noticed.

Some types have one generation per year, and others have two generations. If the scale cover is gray or banded, the scale has one generation and this group hatches in late May. If the cover is brown, there are two generations per season. The first hatches in late May and the second hatches in late July or August. (Source: Iowa State Extension)

To manage scale, timing of practices is important. Prune out and destroy heavily infested branches before eggs hatch. During winter, homeowners can scrape off parent scales, which are filled with overwintering eggs, by lightly rubbing branches with a plastic dish pad. In March or April, before buds expand, spray twigs, branches and stems with horticultural oil to suffocate eggs and reduce hatching. Some plants may be sensitive to oil sprays. Check to make sure a plant is listed on the label before spraying.

Apply labeled insecticide sprays when scale insects are in the crawler stage. Insecticides labeled for control include horticultural oil, insecticidal soap, acephate, bifenthrin or malathion. Repeat application in 7 to 10 days or according to label direction. Repeat again at August egg hatch if needed.

Oystershell Scale, Iowa State University Extension and Outreach

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2. Winter desiccationBe alert in western Nebraska; probably not an issue for eastern parts of the state

Cold, dry, windy winter conditions with little snow cover and extreme winter temperature fluctuations increase winter dessication injury on evergreens because these plants lose more moisture from green foliage during winter. Damage occurs when the amount of moisture lost is greater than can be replaced by roots from frozen or dry soil. Plant tissue dries out resulting in browning of foliage and dieback, which is often not seen until spring. Injury is found on the outer portion of the branches and is most severe on the side of the tree facing the wind or a source of radiated heat, such as a south or west-facing brick wall or street.

Actions that can be taken now are placing burlap wind screens between plants and prevailing winds or radiated heat sources; applying antidessicants according to label directions when temperatures are above 40º F; and watering if soils are not frozen and air temperatures are above 45º F. Prevention includes wise plant selection for the planting site's growing environment, correct summer and fall watering, and avoiding late season fertilization.

When spring arrives, it will be important to remind homeowners not to be in a hurry to prune damaged tissue. While green needles may be brown, the buds on the branches may still be viable and will eventually open. If damage is not too severe and twigs are not killed, the area may eventually fill in. With evergreens, pruning cannot be done past where there is green leaf tissue. If this is necessary, consider replacing the plant with one better adapted to the site.

Green and Growing Tip: Broadleaf Evergreens, Backyard Farmer

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3. Brown marmorated stink bugWarm days result in active insects; stink bugs become an indoor nuisance

Another fairly new invasive pest is brown marmorated stink bug (BMSB) which may be a nuisance in homes. These are a little over ½ inch in length, shield-shaped and brown in coloration. Marmorated means they are marbled or spotted in appearance. We have native brown stink bugs, but their underside is lime green which differentiate between the two. The first find of BMSB in the US was in Pennsylvania in 1998. Since then, this insect has spread to 43 other states including Nebraska, Iowa, Kansas, and Colorado. It was first found in Nebraska in 2010 and is beginning to be widespread.

The main issue most Nebraskans will deal with is annual fall invasion of their home. In fall, stink bugs look for spots to overwinter and our homes have many crevices to hide in. While they won’t breed in the home or damage the structure, they are annoying and smelly. If stink bugs are found inside, vacuum and dispose of them outside. Insecticide foggers are not recommended as these provide little control. To reduce entry in fall, seal entry points. Check for cracks around windows, doors, pipes, and chimneys and seal openings with silicone or silicone-latex caulk. Check screens on doors and windows for holes and to repair trouble spots or replace screens. Insecticides can provide some protection if applied at the correct time of year (fall). A pest control professional should be contacted for help.

All true bugs have needle-like mouthparts used to siphon plant fluids for food. BMSB feeds on many different plants, including common garden crops such as tomatoes and peppers, tree fruits like apples and peaches, and small fruit crops like grapes and raspberries. BMSB can damage fruits and leaves on plants when feeding. This injects saliva and also removes plant juices inducing stippling damage on leaves and necrotic spots on fruits.

Brown Marmorated Stink Bugs, Nebraska Extension 

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4. Spotted lanternflyHas not been found in Nebraska yet; report possible sightings

A new invasive species to be aware of is the spotted lanternfly. It has not yet been found in Nebraska but could be coming this way. Familiarize yourself with what to watch for and report possible sightings to the Nebraska Department of Ag or your local Extension office.

The spotted lanternfly is not a fly or a moth. It is a member of the Hemiptera or true bug order. Adults are 1 inch long and ½ inch wide at rest. The forewing is gray with black spots of varying sizes and the wing tips have black spots outlined in gray. Hind wings have contrasting patches of red and black with a white band. The legs and head are black, and the abdomen is yellow with black bands. Adults, when startled, expose the bright red coloration on their hind wings. When adults are at rest, their gray, spotted color helps them blend in with their surroundings. Early instars (immature stages) are black with white spots. By the last immature stage, the 4th instar, they develop red patches in addition to the black color with white spots. This is the last immature stage before they mature into an adult.

Freshly laid egg masses appear as if coated with a white substance. As they age, the egg masses look as if they are coated with gray mud, which eventually takes on a dry/cracked appearance. Very old egg masses may look like rows of 30-50 brown seed-like structures aligned vertically in columns. Tree of heaven, bricks, stone, lawn furniture, recreational vehicles, and other smooth surfaces can be inspected for egg masses. Egg masses laid on outdoor residential items such as those listed above may pose the greatest threat for spreading this insect via human aided movement. 

The spotted lanternfly has been reported on over 70 species of plants so has a wide host range.  If allowed to spread in the U.S., this pest could seriously impact the country’s grape, orchard, and logging industries. The adults and immatures damage host plants by feeding on sap from stems, leaves, and the trunks of trees. Trees may be found with sap weeping from the wounds caused by the insect’s feeding. The sugary secretions (excrement) created by this insect may coat the host plant, later leading to the growth of sooty mold.  Host plants have been described as giving off a fermented odor when this insect is present.

To learn more - Spotted Lanternfly, Nebraska Invasive Species Program

Spotted Lanternfly, United States Department of Agriculture

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5. Magnolia scaleScout plants with a history of infestation

If customer trees had magnolia scale last year, winter is a good time to scout and determine the status of the infestation for this year. It's likely infested plants will require more than one year of treatment. 

Magnolia Scale, Morton Arboretum
Green and Growing Tip: Dormant Oil Spray, Backyard Farmer
Scale Insect Control, Backyard Farmer

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6. BagwormEncourage clients to remove last year's bags from high value small trees

Encourage clients now to scout plants affected last year. Remove and destroy bags on high value, smaller evergreen trees will help reduce next year's bagworm population. Bags can be removed from now until insects hatch next year, approximately mid-May. Destroy bagworm eggs by removing bags from the plant and crushing or immersing them in soapy water. If bags containing eggs are discarded on the ground, eggs may survive winter fine then hatch and larvae return to the surrounding plants next summer. As many as 500 to 1000 eggs can overwinter in one female bagworm's bag. 

Bagworms, Nebraska Extension
Bagworms, Backyard Farmer

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7. Pruning trees & shrubsGood pruning practices - timing and techniques - essential for plant health & productivity

Trees - New research shows the optimum time to prune living branches is late spring and early summer because pruning at this time promotes the quickest sealing of pruning wounds. Late spring and early summer is when tree cells are most active during the growing season, hence sealing occurs the quickest. However, professionals may not have a choice to limit pruning to this time frame, due to the total amount of tree work needed by clients, or when pruning is needed to repair tree damage after a wind or ice storm. Oaks are best pruned during winter - December, January or February - to avoid potential infection with oak wilt. 

Pruning Shade Trees In Landscapes, Edward Gilman, University of Florida
ANSI A300 Pruning Standard, International Society of Arboriculture
Best Management Practices - Utility Pruning of Trees, International Society of Arboriculture
Structure Pruning, Backyard Farmer

Shrubs - Prune summer-flowering deciduous shrubs during dormancy, typically late February or March; examples include spirea, potentilla, and smokebush. Spring-flowering shrubs should be pruned when blooming is finished; this includes forsythia, weigela, mock orange, lilacs and viburnums (Koreanspice, Arrowwood, European cranberrybush, etc.). 

Pruning Ornamental Trees and Shrubs, Purdue Extension

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8. Pruning fruit treesTime pruning on tree species

Productive fruit trees, with an abundance of high quality fruit, do not just happen. They result from good cultural practices, including pruning. However, fruit tree pruning is often neglected either due to a lack of pruning skills and knowledge, or a fear that the tree will be damaged or killed by incorrect pruning.

Most fruit tree pruning is done during the dormant season when no leaves are on the tree. March is the best time to prune. Cultivars or tree species susceptible to winter injury, such as peach and apricot, are best pruned in late spring before growth begins, rather than in January or February. Regardless of the cultivar grown, do not prune any tree before January or winter injury can occur.

Besides dormant pruning, trees may be prune at planting; during July and early August to restrict growth; remove water sprouts; or remove diseased or damaged wood. Once the basic structure of a fruit tree is developed, avoid pruning until fruiting occurs. For information on how to prune different fruit trees, see the resource links below.

Pruning Fruit Trees, Nebraska Extension
Apple Tree Pruning, Backyard Farmer
Winter Peach Tree Care, Backyard Farmer

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Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Nebraska Extension is implied. Use of commercial and trade names does not imply approval or constitute endorsement by Nebraska Extension. Nor does it imply discrimination against other similar products.

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  • Emerald Ash Borer Resources - EAB has been found in the following Nebraska locations. 2016 - Omaha and Greenwood, NE; 2018 - Mahoney State Park and Lincoln, NE. 2019 - Ashland. Homeowners are encouraged to wait to begin treating their ash trees until the insect is confirmed within 15 miles of their location. 

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