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Hort Update for February 15, 2021

Vole damage in turfgrass. Hort Update for February 15, 2021, Nebraska Extension,
Vole damage in turfgrass
Serious ConcernsMajor Symptom
1. Invasive plant species What are they and what impacts do they have? 
2. February growing degree days (GGD) Omaha 2/9/21 GGD -  2,  Understanding Growing Degree Days
Timely Topics
3. Winter damage to evergreens Watch for browning of foliage on the south or east side of evergreens
4. Continued protection from wildlife damage needed Scarce food sources and rising snow cover make wildlife damage to landscape trees and shrubs likely this winter.
5. Understanding seed potato restrictions for Nebraska gardeners Columbia root knot nematode protection for Nebraska's potato industry
6. Reapply antidesiccants Reapply when temperatures are above 40 degrees F., make another application to evergreens and broadleaf evergreens at high risk of winter desiccation.
7. Get ready for fruit tree pruning Would closure is fastest if pruning is done just before growth begins in spring
8. Pantry pests Clients may experience indoor pest problems due to improperly stored seed following February's national bird feeding month

1. Invasive plant speciesWhat are they and what impacts to they have?

As awareness increases about invasive species, clients may ask if a plant is considered an invasive species before they purchase it. Invasive species are non-native species (plants, insects, fish, etc.) whose introduction causes or is likely to cause harm to the economy, environment, or human health.

Does Invasive Species = Noxious Weed?
Invasive plant species may or may not be designated a noxious weed by the Nebraska Department of Agriculture. This designation is based on the impact of the plant in its new environment. For example, purple loosestrife is an invasive species that has been designated a Nebraska noxious weed. As such, it is illegal to sell or plant and people that have it growing on their property are required to destroy it.  Purple loosestrife was determined to be noxious due its impacts on waterways and ecosystems.

Plants considered to be invasive species, but which have not been designated a noxious weed by a county or state, can still be sold and planted. However, because of the harm they cause, knowing which plants are on your state's invasive species and watch lists, and why, is wise. For Nebraska, these lists can be found at . They include some plants found in landscapes such as callery or ornamental pear (Pyrus calleryana), tatarian honeysuckle (Lonicera tartarica), Japanese honeysuckle (Lonicera japonica), Tree-of-heaven (Ailanthus altissima) and St. Johnswort (Hypericum perforatum).

Species Level Identification Critical
It is important to know the genus and species name of plants considered invasive species. For example, while oriental bittersweet (Celastrus orbiculatus) is listed, American bittersweet (Celastrus scandens) is not. The same is true for St. Johnswort. Hypericum perforatum is on invasive species lists but Hypericum kalmiamum is not. Clients concerned about invasive species may hear that St. Johnswort is an invasive species and ask why you are selling or recommending them. 

To help understand the impacts of invasive species, below is the article “How do Invasive Species Cause Harm” from eXtension, a national Cooperative Extension resource.

When a non-native species is introduced into a new environment it is freed from the natural predators, parasites, or competitors from its native habitat. This gives an advantage to non-native species competing with the native species that evolved in the ecosystem. These advantages allow the non-native species to outcompete native species for the available food, water, light, and space. Wherever an invasive plant is growing is where a native plant should be”.

Invasive species also have the potential to disrupt vital ecosystem functions, such as water flow, nutrient cycling, fire systems, or soil composition. An example of this is the Tamarix species. Note: Saltcedar (Tamarix ramosissima) is a Nebraska noxious weed. It not only uses large amounts of water, it changes the soil chemistry, making it more saline. This can adversely affect and prevent the growth of many native plant species. Tamarix has significantly changed the hydrology, soil composition, and plant communities of many habitats in the western United States. An invasive plant may add significantly to the fuel load of an area, either in mass or because it contains volatile compounds. This can mean that fires burn hotter and faster than the native plants in that habitat have evolved for. After such a fire, the invasive plant quickly germinates or resprouts while the native plants are either killed or perhaps recover much more slowly.

Changes that damage native plant communities also affect the wildlife communities that depend on them for food and shelter. A wide range of effects have been seen in wildlife communities in these situations. Some animal species populations are reduced while others are increased. Some are even pushed to the point of extinction. But the overall trend seems to be a reduction in diversity. Even in cases where the same number of species are actually present, the balance between the species has been changed. We do not yet know what many of these changes herald for the future.

Invasive species can damage or contaminate crops from soybeans to pine plantations, greatly increasing costs to the agricultural industry and, in turn, to the American public for both food and other products. Industries such as the cattle industry can be affected when invasive plants that are basically inedible by cattle, infest ranges or contaminate forage. Other services such as electricity have cost increases resulting from the management and control of invasive species. A great deal of money is spent by power companies to keep invasive plants from growing in right of ways, up poles, onto buildings, and along power lines under control.

Natural areas used for recreation can be affected by invasive species. For example, Chinese privet and other invasive shrubs, trees, and vines can take over both clearings and the understories of forests making hunting, hiking, biking, and camping difficult or impossible.

Any body of water, river, or stream is especially vulnerable to invasive species. Water by its nature allows for much easier movement for invading organisms. The news has many examples of aquatic-invasive species that can and have spread very quickly causing significant changes in a very short period of time. From water hyacinth to lion fish or Asian carp, aquatic species are causing damage to these ecosystems and the organisms that inhabit them. It is often difficult, and sometimes impossible, to fish, boat, or swim on a lake covered by invasive plants. People have been hospitalized due to injuries received while boating on rivers infested by the Asian carp, which can easily leap over a boat”.


3. Winter damage to evergreensWatch for browning of foliage on the south or east side of evergreens

Cold, dry, windy winter conditions with little snow cover and extreme winter temperature fluctuations increase winter dessication injury on evergreens, especially arborvitae and boxwood, but also pine, spruce, fir, juniper and yew, because evergreens lose more moisture from green foliage during winter than deciduous plants with no foliage.

Damage occurs when the amount of moisture lost is greater than what can be replaced by roots, often due to 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.

Winter Desiccation, Nebraska Extension


4. Continued protection from wildlife damage neededScarce food sources and rising snow cover make wildlife damage to landscape trees and shrubs likely this winter.

Higher snow layers enable wildlife to reach over low protective mesh. It's important to keep protection at least two feet higher than the surrounding snow layer to prevent rabbit damage. Mesh should also be fine enough to prevent vole access to the base of trunks and stems. 

Managing Deer Damage in Nebraska, Nebraska Extension 
Managing Rabbit Damage, Nebraska Extension
Excluding Rabbits, Backyard Farmer
Controlling Vole Damage, Nebraska Extension
Vole Control, Backyard Farmer


5. Understanding seed potato restrictions for Nebraska gardenersColumbia root knot nematode protection for Nebraska's potato industry

Nebraska Department of Agriculture has a quarantine in place for our state to protect the Nebraska potato industry from the Columbia root knot nematode. Nebraska has quite a large commercial potato growing industry. If the nematode became established here, it could have a serious impact on the potato growers in our state. 

To ship seed potatoes into Nebraska, growers have to get a certification, which involves having their state’s Department of Agriculture conduct official sampling & testing for presence of the nematode where the seed potatoes are grown. Then the state has to issue a phytosanitary certification for each shipment of potatoes. Some mail order nurseries don't purchase their seed potatoes from certified growers, so cannot ship to Nebraska gardeners. Gardeners should look for a nursery who's seed potatoes are grown in North Dakota, Wisconsin, Minnesota, Michigan, and Maine (some of the bigger seed potato states in the non-infested areas). They would not be subject to the quarantine requirements.

Take a look at the publication below for additional mail order sources.
General and Specialty Mail Order Seed Sources, Nebraska Extension


7. Get ready for fruit tree pruningWould closure is fastest if pruning is done just before growth begins in spring

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 just before growth begins, late March or early April. 

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


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.