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Hort Update for December 17, 2019

Hort Update for December 17, 2019, Nebraska Extension, http://communityenvironment.unl.edu/update12172019
Natural needle drop in white pine.
Serious ConcernsMajor Symptom:
1. Deer damage Prevent damage before it occurs
2. Vole damage Feeding can girdle and kill trees or shrubs
Minor Issues
3. Trees holding leaves May increase the potential for tree damage if heavy snow or ice storms occur
4. Delayed natural needle drop Uniform browning in fall of interior evergreen needles
5. Dormant lawn seeding Good seed-soil contact important for dormant seeding success
Timely Topics Major Points:
6. Dormant season lawn irrigation Monitor turfgrass for dry winter conditions
7. Houseplant insect issues Success relies on early detection and effective controls
8.Pesticide storage & safety Read and follow label directions for safe storage conditions



1. Deer damagePrevent damage before it occurs

Deer browse a variety of plants, especially when populations are high or forage is limited. Browsing by deer is identified by jagged or torn edges of twigs or stems and can occur from the ground up to 6 feet. Male deer also rub antlers against trees in the fall, which can kill or severely damage trees.

For nurseries, where reliable protection is needed, fencing can be very effective in preventing and reducing deer damage. Permanent, high-tensile, woven-wire fences have been used for years to control deer damage and are considered the “gold standard” of fencing. They are the most expensive to build, but require little maintenance. See information on fencing at the link below or at the Internet Center for Wildlife Damage Management (ICWDM).

In landscapes, deer damage may be reduced by selecting plants with thorns, thick bark, or through application of chemical compounds that make plants less attractive to deer. The Morton Arboretum provides a list of plants not favored by deer. No plant is entirely deer-proof, but selection of less attractive species may lower damage to a tolerable level.

Chemical repellents affect smell, taste, and pain receptors of deer and should be applied directly on the plant or nearby. They may work for a short time and reapplication is needed. If forage is limited, deer will eat a bad smelling or tasting plant over going hungry. A list of repellants and how they work is provided in the NebGuide linked below.  

Deer adapt quickly to frightening devices. Research shows propane cannons, deer guards, shell crackers, and lasers are ineffective at reducing deer damage. Moreover, audio and visual frightening devices that use noise may cause problems with neighbors in suburban areas.

Managing Deer Damage in Nebraska, Nebraska Extension

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2. Vole damageFeeding can girdle and kill trees or shrubs

Vole feeding can girdle and kill trees and shrubs, usually in late fall and winter. Gnaw marks of voles are irregular in appearance and at different angles. Depending on the type of vole, voles create surface runway systems or burrows.

Trapping is an effective method for vole control if damage is over a limited area (less than an acre) and a sufficient number of traps are used (two to three per runway and/or hole). Set single mouse snap traps perpendicular to vole runways with the triggers in the runways, or set two traps together within the runways with triggers facing away from each other. Bait is not required. If you use bait, smear peanut butter mixed with oatmeal on trap triggers. Cover baited traps with a box with a 1-inch hole cut in it, to reduce access to birds and squirrels. Make sure boxes are secured. Trap enclosures can also be made of PVC pipe. Multiple-catch mouse traps are useful since several voles can be captured at one time. Locate traps near visible burrows and adjacent to vole trails. Place a small amount of seed material, either bird or grass seed, at both entrance points. If the location is correct, traps should contain a few voles in 24 hours. If you catch nothing after two nights of fair weather, move the traps to a new location.

Exclusion can be used to protect highly valued trees. Use ¼-inch hardware cloth or plastic cylinders to protect individual trees and shrubs. The cylinder should be tight to the ground or buried about two to six inches and extend to a height above expected snow depth. When making the cylinder, overlap the edges at least 1 inch and fasten securely so gaps do not form.

Habitats can be modified to reduce suitability for voles. High vole populations cannot become established without food and protection from predators. Control grass and weeds around young trees and shrubs through cultivation, herbicides, and mowing. Since voles often thrive under plastic weed barriers, remove these or use other control methods listed below. Remove bird feeders or substantially reduce spillage from feeders to avoid attracting voles.

Repellents provide short term protection unless reapplied. Those made with thiram and capsaicin are registered for controlling vole damage on ornamental plants only. Coyote and fox urine may help to disperse voles and have been proven to increase stress and, therefore, reduce reproduction in voles. Wear waterproof gloves and avoid contact with urines as they may not be sterile.

Controlling Vole Damage, Nebraska Extension
Vole Control, Backyard Farmer

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3. Trees holding leavesMay increase the potential for tree damage if heavy wet snow or ice storms occur

Deciduous trees retaining leaves into winter is known as marcescence. Oaks, American beech and ironwood typically hold their leaves into winter. When other trees, like maple, retain brown leaves, it is because the natural process of abscission, where a separation layer develops between the leaf and the twig, was interfered with. Temperature extremes and early snowfall are some reasons. This is not harmful to trees. The main concern is the increased potential for snow and ice loads leading to potential branch failure. Not much can be done but to be aware of the increased risk during and after snow storms.

Immediate Care of Storm Damaged Trees, Nebraska Forest Service

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4. Delayed natural needle dropUniform browning in fall of interior evergreen needles

Older needles on the inside of evergreen trees are shed each fall after they turn yellow, brown or reddish tan in color. Sometimes this natural process is very subtle and goes unnoticed because only the inner most needles area affected, as in the picture below. Pine trees can hold their needles for 2-5 or more years, depending on the species. Spruce trees generally hold onto their needles longer than pine trees do, approximately 5-7 years.

This year some evergreens seem to be holding on to their needles longer than normal, resulting in delayed drop. This may be due to early cold temperatures parts of the state experienced in conjunction with our October snow. Early cold, before the natural formation of an abscission layer has occurred, may have caused needles to stay attached longer than usual. There is no cause for concern or potential negative impact to affected trees. 

However, if there is question about a potential pathogen causing browning needles and needle drop, contact your local Extension office or submit pictures through UNL's Digital Diagnostic Network

Natural Needle Drop, Nebraska Extension
Evergreen Needles Are Falling, Iowa State Research and Extension

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5. Dormant lawn seedingGood seed-soil contact important for domant seeding success

Dormant seeding is defined as such because seed lies dormant until soil temperatures warm in April or May. It can be done as early as Thanksgiving or as late as March in most Nebraska locations. The key is to seed after the soil is cold enough that germination will not occur until after soils warm in spring. The benefit of dormant seeding is as soil heaves and cracks during winter, crevices are created for seed to fall into, providing ideal germination conditions in spring. Dormant-seeding may be easier to schedule than spring seeding, because spring rains can make it difficult to seed after March.

There are risks with dormant seeding. It is most effective if weather remains cold enough to delay germination until spring. Occasionally, extended warm periods in winter could allow seed to germinate, and seedlings may then be killed by ensuing cold weather.

As with any seeding, soil preparation needs to be done prior to seeding. For dormant seeding, this would be in fall before the soil freezes or during dry winter periods when the soil is not frozen. If using dormant seeding, monitor the area in mid spring for the need to do additional over-seeding.

Establishing Lawns from Seed, Nebraska Extension Turf iNfo

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6. Dormant lawn irrigationMoitor turfgrass for dry winter conditions

Thus far this winter, we have just enough snow and rainfall to prevent turf water shortages and winter dessication. This type of injury most commonly occurs from January through March, during periods of very cold temperatures with little snow. Be aware of the potential for injury when there is little snow cover; or if temperatures warm and precipitation decreases.

Desiccation injury is usually greatest on exposed or elevated areas where surface water runoff is great. It is also prevalent on poorly rooted turf that cannot take-up water from deeper in the soil profile. Turf management professionals need to monitoring turfgrass sites for dry conditions.

If winter irrigation is used, only water when the soil is not frozen and air temperatures are above 40 degrees F. Lightly irrigate high value turf on dry sunny days when the air temperature is well above freezing where feasible.  The goal is to rehydrate plant crowns (and lower leaves) back to a survivable level and restore soil moisture at the surface.  Avoid excessive quantities of water which may fill soil pores or runoff and present an icing hazard when cold temperatures return.  Also avoid trafficking high value turf areas as winter drought, like summer drought, increases the risk of traffic injury.  To prevent crown hydration injury, avoid watering before a sudden temperature drop is forecast, when the ground is frozen, or in low areas where water might collect and stand due to frozen soil or poor drainage.

Fighting Dessication: Should we water turf in winter?, Nebraska Extension

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7. Houseplant insect issuesSuccess relies on early detection and effective controls

Houseplants are susceptible to several common insect pests, including spider mites, white flies, scale, mealybugs, fungus gnats and thrips. Gardeners should inspect plants each time they water to look for signs of trouble. 

Managing Houseplant Pests, Colorado State University Extension

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8. Pesticide storage & safetyRead and follow label directions for safe storage conditions

Store pesticides correctly and securely.  Storage information can be found on pesticide labels.  Read and follow it for safety and to help keep pesticides from degrading so they may no longer be as effective.

In general, pesticides need to be stored in a secure, well ventilated location that can be locked. The location should be away from children, pets and food items as well as anything that might be contaminated in case of a leak or accidental spill. 

Do not store pesticides near heat, sparks, or open flames; and check that containers are tightly closed. Always store pesticides in their original containers.  A mistake made is pouring a pesticide into a container other than the original. This is against pesticide label law and has led to accidental poisonings. 

A common question about winter storage is if a pesticide is still effective after it freezes.  Most pesticides are safely stored between 40 and 100 degrees Fahrenheit, but it is best to check the label for storage temperature requirements and any warnings against freezing.  If a liquid pesticide does freeze, it might be less effective in controlling pests. 

Pesticides contain active and inactive ingredients. The active ingredient is what kills the pest. Inactive ingredients include solvents, carriers, or emulsifiers that make the pesticide more efficient. Due to some inactive ingredients, the freezing point of some liquid pesticides could be lower than 32 degree F. Read the label for temperature storage requirements and what to do if a pesticide does freeze.          

Pesticides formulated as wettable powders or granules are not affected by low temperatures. However, moisture can cause caking that may reduce effectiveness so follow label directions for correct storage recommendations. If you have products formulated in water-soluble packets, these should not be frozen as they tend to become brittle and then break open.

Safe Transport, Storage, and Disposal of Pesticides, Nebraska Extension

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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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