Hort Update for November 11, 2016

Lawns
Major Symptom:
1. Leaf mowing Mulch mow leaves into turf; good source of organic matter and phosphorus
2. Snow mold Fungicide lawn treatment not recommended in Nebraska
3. November irrigation 1/4" of water per week if temperatures remain warm
4. Kentucky bluegrass stem rust Orange-red powder in lawn; not a problem for lawns
5. November fertilization

With warm temperatures, quick release Nitrogen sources recommended

6. Broadleaf weed control Triclorpyr still being used; avoid mowing 3 days prior to application
   
Trees & Shrubs  
7. Fall watering Water evergreens if soil dry to reduce winter drying
8. Wildlife protection Use exclusion or repellant methods correctly
9. Sunscald prevention Properly wrap trunks of young tender barked trees
   
Landscape Ornamentals  
10. Vole control Protect trees and use traps for vole monitoring
11. Mulch fall-planted perennials Winter mulch improves survival for some perennials
12. Rose winterization Mulch, prune if needed after plants are dormant; best to prune in spring if possible
13. Clean up diseased plants Fall sanitation is very important to reduce disease pressure next year
   
Fruits & Vegetables  
14. Soil amendment & green manure Safe application of manure or compost in fall
15. Vegetable garden and fruit cleanup Helps control diseases and pests
   
Miscellaneous  
16. Anti-desiccant application Delay 1st application until late November
17. Mouse control Effective control involves sanitation, exclusion and population reduction
18. Featured NebGuide Winter De-icing Agents for the Homeowner

1. Leaf removal or mulch-mowing into the lawn is important to prevent leaves matting and suffocating turfgrass during winter. It also keeps leaves from clogging storm drains to cause localized flooding; and from being transported to surface water where they cause pollution. Mowing leaves into the turf works as long as the leaf layer is not too thick. Tree leaves should be pulverized enough that they filter down into the turfgrass. After mowing, green grass blades should still be visible. A mulching mower works best. A regular mower can be used as long as the leaf layer is not too thick. Clients are sometimes concerned about thatch build-up. Tree leaves will not contribute to thatch; which is mainly a layer of dead roots and rhizomes which are high in lignin and do not decompose as readily as grass clippings and pulverized tree leaves. Tree leaves mowed into the turf are also a source of organic matter and the nutrient phosphorous (P).  

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2. Snow mold is a minor fungal disease that can develop on turf under specific conditions. However, fungicide treatment for home lawns is not recommended in Nebraska. Snow mold is more likely to develop if turfgrass remains taller than 3.5” going into winter, under tree leaf layers, or if snow falls, and remains, on turfgrass that is not dormant. Mowing as long as the grass is growing, tree leaf removal, or mulch mowing leaves into the turf are adequate snow mold prevention methods.

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3. November and winter irrigation - Watering in November, if needed, can help prevent winter dessication. At this time of year, and on warm winter days, one-fourth inch of water a week is enough to avoid dessication. Water early in the day so water soaks into soil.

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4. Kentucky bluegrass stem rust is a fungal disease that develops late in the season on lawns with slow growth due to low nitrogen. The obvious symptom is rust colored "powder" (fungal spores) on grass blades, shoes and lawn mowers. Heavily infected turf may show yellowing of grass blades. Fungicide controls are rarely recommended or needed for home lawns. Fall lawn care, especially correct nitrogen fertilization, along with cooler fall weather promotes turfgrass growth and rust disappears. Cold temperatures also kill the fungus.

Note for sports turf - If stem rust occurs on low maintenance athletic fields, the fungal spores can cause problems for allergy/asthma sufferers. Control of stem rust is recommended on sports turfs using a combination of wise turf management and timely fungicide applications. It is too late this season for fungicide controls.

Leaf Rust, Purdue Extension

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5. Fall fertilization with nitrogen is best done by the end of October.  Due to warm air and soil temperatures, fertilizer products with fast release (water soluble) sources of nitrogen continued to be used into November. This is fine. Examples of fast release nitrogen sources include Urea, Ammonium sulfate, any source listed as ammoniacal or water soluble. Fertilization should typically not be done in November, or later, to reduce the risk of nutrient leaching or runoff. Unless a soil test shows the need for phosphorous, avoid applying this nutrient to turfgrass.

Transition from Slow to Quick Release Nitrogen, Nebraska Extension

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6. Perennial broadleaf weed control – How late? As temperatures become colder, the process of herbicide movement and weed kill slows, but can still be effective as long as the weed has green leaves. The herbicide Triclopyr has continued to be used on broadleaf weeds into November this year. The recommendation is to avoid mowing for three days prior to application. Research is currently underway to evaluation this recommendation.

Broadleaf Weed Control, Nebraska Extension

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7. Fall watering - Our warm fall has been fairly dry. Monitor soil moisture of evergreens and newly planted trees. In the absence of rain, watering may be needed to ensure the soil remains moist up until it freezes to help avoid winter drying.  Adequate fall moisture is the most important factor to reducing the risk of winter injury from dessication. Moisten the top 6 – 8 inches of soil around the tree. Water early in the day so water soaks into soil before nightfall to avoid water freezing around stems. Year round, use a 2 – 4” layer of mulch around the tree, but not up against the trunk, to conserve soil moisture.

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8. Wildlife protection for young and valuable tree - Barriers of hardware cloth placed around young trees and shrubs is the best means of protection from rabbit and vole damage. Make sure barriers extend well above the average snow line. Various taste repellants, such as Thiram or Millers Hot Sauce, can be effective in reducing deer and rabbit damage as long as animals have other food sources to turn to. Scent repellants, such as bags of human hair or bar soaps on a rope, have been shown to be effective in some situations.

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9. Sun scald commonly occurs on young, tender barked trees, such as Maples, during winter. It may be due to uneven heating of the trunk; however, there appears to be a correlation to root damage during transplanting. Proper planting and post planting care may be more important to protecting trees from sunscald than tree wrap. If used incorrectly, or left on too long, tree wraps can cause more harm than good. If used, tree wraps should be attached in late November/early December at the soil line and the tree wrapped upward with the wrap overlapping up to the first set of branches; then removed in spring. Leaving wraps on too long may girdle or compress the trunk, reduce photosynthesis, and increase insect (borer) damage. Avoid the use of paint as these may cause chemical damage to the trunk.

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10. Vole control - If we receive enough snow cover this winter, voles may turn to trees and shrubs for a food source, gnawing on tree bark and roots, and potentially killing plants. To help prevent this, keep tall grass and weeds removed from around the trunk of trees and avoid mulch layers deeper than three inches. Placing hardware cloth around tree trunks will prevent vole feeding. Check for and trap voles by placing baited mouse traps inside PVC or other pipe near trees. Insert the traps far enough into the pipe so that pets, birds and other animals are unable to reach the trap. Check the stations once a week and reset traps as necessary.

Vole Damage, Nebraska Extension

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11. Mulching fall planted perennials – Winter mulching is recommended for strawberries, Chrysanthemums and other perennials on the borderline of hardiness for a given area; and for fall planted perennials to help prevent frost heave uprooting plants. Winter mulch should be put into place after plants are fully dormant and soils begin to freeze or night temperatures are consistently dropping into the 20s, usually around mid November. However, this fall temperatures have stayed warmer than normal, so wait to apply winter mulch until the soil is cold. Waiting to apply mulch when the soil is cold is much better for plants than applying it too early. Early to mid December is not too late to apply winter mulch.

Use a 12 inch layer of coarse mulch over the tops of plants. Encircling plants or beds with chicken wire and filling the chicken wire with coarse mulch, such as wood chips or leaves, works well.

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12. Rose winterization - Pruning is not needed during fall for shrub and hybrid tea roses unless some pruning is needed for a rose to fit beneath a winter protection method, such as a rose cone. Wait until April and then prune to remove winter killed wood.

Hybrid tea roses benefit from extra winter protection, but shrub roses usually do not require it. Do not add winter protection to roses until the soil begins to freeze or night temperatures are consistently dropping into the 20s at night. One good mulching method is the encircle the rose with a chicken wire cage, staked to hold it in place, then fill the cage with coarse leaves. Soil can also be mounded up around the base of a hybrid tea rose to provide extra cold protection for the graft union.

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13. Clean up diseased plants - Diseases were prevalent on some garden plants this year, particularly powedery mildew on peonies. Practice good fall sanitation to reduce the amount of overwintering fungi. Cut off this year's stems and foliage, and discard it. Don't add it to the compost pile. If plants develop a history of repeated infections, fungicide applications may be warranted next year, but usually plants survive quite well even with yearly infections.

Powdery Mildew on Landscape Plants, University of Nebraska-Lincoln

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14. Soil amendment & green manure - incorporating compost or manure is a good way to improve garden soils. The addition of organic matter improves drainage in clay soils and the water holding capacity of sandy soils. It adds essential nutrients and increases beneficial microorganisms. However from a safety standpoint, manure must be handled and applied correctly. Only apply manures that have been aged for at least six months to minimize the risk of burning plants with excess ammonia. It is best to use manures that have been properly composted (to a temperature of at least 140 F.) to kill harmful E. coli bacteria that may be present in raw manure. Proper composting is critical for using manure in food gardens to avoid potential human illness. Manures from carnivorous animals should never be used. Additionally, if soils have high levels of salts, feed lot manure should be avoided as they will add to the problem.

Compost from lawn and garden plant materials carry a much lower risk of food pathogen.  But avoid using plants heavily infected with disease in your compost pile; disease pathogens may survive the composting process and infect plants the following year.

Using Manure and Compost as Nutrient Sources for Fruit and Vegetable Gardens, University of Minnesota Extension
Choosing a Soil Amendment, Colorado State University

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15. Vegetable garden and fruit cleanup involves cleaning up or tilling under plant debris in the vegetable garden and around fruit trees to reduce overwintering pests. The sooner this can be done after a plant dies or after fruit drops to the ground, the better. Plant pathogens are less likely to survive if organic matter is quickly decomposed. Remove plant debris or infected plant parts after each growing season.

  • Turn the soil after harvest to help break down small roots that may harbor nematodes, fungi or bacteria.
  • Gardeners may compost dead plants if they have a good composting system; otherwise, these piles may serve as a source of pathogens.
  • Prune or remove twigs and branches of woody plants affected with fire blight and other bacterial or fungal canker diseases.
  • Keep gardens weed free. Weeds often are another source of pathogens. Eradicate weeds to break the life cycle of pathogens and control them. Weed removal also can increase air movement and thus decrease conditions that favor disease development.
  • So that pathogens do not spread from one area to another, always disinfest machinery and other tools with steam, hot water under pressure, or a 10 percent solution of household bleach diluted with water.

Orchard sanitation is essential for good maintenance of fruit trees and small fruit plantings. Insects and diseases can overwinter on dead or infected plant material. Dried fruits or "mummies" carry disease organisms through the winter to attack next years' crop. Remove and destroy any fruits that have fallen to the ground, or those appearing to rot on the branches.

Non-chemical Control of Disease, Colorado State University

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16. Anti-desiccant application - Also known as anti-transpirants, these products help plants endure stressful periods by reducing transpirational water loss from foliage. The most common types of anti-desiccants are an emulsion of wax, latex, or plastic that forms a thin film on foliage to minimize water loss from plants. We recommend their use on evergreen conifers or broadleaf evergreens in winter, particularly on plants with a history of winter desiccation injury or plants suseptible to winter drying like arborvitae, holly and mahonia. Select the right product for the plant species as there are toxicity issues. Read and follow label directions.

Apply the product once every six weeks, beginning after plants have completely hardened off in late November. Continue through mid to late February. Avoid covering plants so heavily they become sticky with needles glued together. Have warm, soapy water nearby and clean out the sprayer immediately or equipment may be ruined by the product.  One common anti-transpirant available through nurseries and gardens centers is called Wilt-Pruf, but other products are available.

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17. Mouse control - House mice are well adapted to life around people. They are commonly found living in and around homes, farms, urban lots, open fields and agricultural lands. Effective control involves sanitation, exclusion and population reduction. More information on mouse control is available in the following publication.

Controlling House Mice, Nebraska Extension

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18. Featured NebGuide - Winter De-icing Agents for the Homeowner, Nebraska Extension

Slick sidewalks and roads are hazardous. Removing compacted snow and ice with shovels or snow blowers is not always an easy task. Deicers can help by “undercutting,” or loosening the snow or ice because they lower the freezing point of water. However, deicers can affect plants so use them with care.

Do not use deicers to completely melt snow or ice, but to make their removal easier. Deicers melt down through the ice or snow to the hard surface, then spread out underneath. This undercuts and loosens the snow so shoveling and plowing can be done.

Research has shown that the shape of deicing particles affects the speed of their penetration through ice. Uniformly shaped spherical pellets of about 1/16” to 3/16” penetrate ice faster and more efficiently than other shapes. Irregularly shaped particles tend to melt randomly in all directions. Flakes melt as much horizontally as they do vertically.

Five chemicals commonly are used as deicers. They can be used alone, they often are blended together or combined with other materials to enhance their performance.

Read More

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Seasonal information for Nebraska's green industry professionals.

Continuing Issues

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