June 29, 2007

Integrated management of eastern redcedar incorporates cultural, mechanical, biological and chemical tools to keep this invasive tree under control and protect grassland production and profits. We recommend using tree height to determine which control options will work best. Burning, cutting, digging, mowing, burning, goats and broadcast herbicides are effective on trees up to 2 feet tall. Cutting and individual-tree herbicide treatments work well on 2-10 foot tall redcedar. Trees over 10 feet tall are most effectively and economically controlled by cutting. The bottom line is "control trees while they are small."

History and Biology

Berries on eastern redcedar. (USDA-NRCS PLANTS Database / Herman, D.E. et al. 1996. North Dakota tree handbook. USDA NRCS ND State Soil Conservation Committee; NDSU Extension and Western Area Power Admin., Bismarck, ND.)

Eastern redcedar (Juniperus virginiana L.) is one of 13 juniper species native to the United States. It is the most widespread tree sized conifer and is native to every state east of the 100th meridian. Throughout this vast range, eastern redcedar grows on many soils and under varying climatic conditions. Eastern redcedar is a dioecious species, which means individual trees are either male or female. Staring in the sixth or seventh year of growth, female trees produce small, berrylike fruits that are eaten by many birds and some small mammals, which indirectly helps spread the seed via droppings. Digestion actually improves germination.

Impact of Eastern Redcedar

Eastern redcedar is a problem on grasslands primarily because it reduces forage production and livestock handling. Developing trees alter the microclimate, which encourages a shift from desirable warm season native grasses to introduced cool season grasses such as Kentucky bluegrass. On many sites complete coverage by eastern redcedar can be expected, resulting in total loss of grass production. Control measures should be initiated as soon as possible, both to improve effectiveness and reduce control costs.

Integrated Management

Integrated management means developing a program which incorporates the best method or methods for a particular site. Management of eastern redcedar infestations is best viewed as a long term effort, both to reduce initial infestations and to prevent them from redeveloping to economically damaging levels.

The emphasis should be on managing the infestation, rather than eradication. Eradication is not economical, and probably not physically possible in most cases. At low levels, eastern redcedars can be viewed as a potential resource, providing livestock shelter, wildlife habitat, timber products, and aesthetic values. Most important, long term selective management is considerably less expensive than a more intensive, short term approach.

If the goal is to just reduce overall number of trees, and stop further spreading, cut female trees only. Female trees produce the berry-like fruits. Saving only male trees provides much needed cover for wildlife, while reducing further spreading.

Manual and Mechanical Control

Manual and mechanical control involves digging, cutting and mowing. It is most efficient on trees up to 2 feet tall. Cutting is an effective method of control because eastern redcedar is a non sprouter. Trees cut below the lowest branches will not regrow. A variety of handheld or motor-powered cutting tools can be used. Hand-held tools (shears, saws, spade, shovel, heavier hoe) are effective on trees under five feet, while a chain saw or vehicle mounted shears are needed for larger trees. The equipment varies from tractor pulled PTO driven shredders to hydraulic drive devices that mount on skid steer loader. All cut trees should be gathered and burned or permanently removed from the grassland.

Biological Control

Biological control is the use of natural enemies to reduce weed populations to economically acceptable levels. In the case of red cedar control, goats can be utilized as an effective bio-control agent for trees that are up to 3-4 ft tall. Experience in Nebraska suggests that goats in a paddock grazing system could kill most cedar trees less than 24 inches tall. Control was reduced by 50 percent on trees 4-8 feet tall, however the goats managed to defoliate bottom branches and stripe bark from branches and trunks up to three inches in diameter.

Generally, goats are browsers with diets consisting of about 70% of non-grassy species, which indicates that they should not compete with cattle for grass. The grazing strategy with goats should vary depending on the management goals for the pasture. Adding one or two goats per cow and letting the goats and cattle run together is an excellent maintenance strategy for pastures with moderate to low cedar infestation; however, if the goal is to get a quicker response and to suppress denser stands, temporary fencing should be used. In this case, the stocking rate should be at least 10 goats per acre. Using this stocking rate with moderate cedar infestation should result in significant damage to the trees within 30 days. Higher stocking rates would be better, but will require moving the fence more often. Trees and other perennial plants have high energy reserves in their root systems and repeated defoliation over several years is required. Cedar trees however, will not resprout and thus, if the goats remove most of the needles

Prescribed Fire Control

This method is inexpensive and very effective against smaller trees. Its effectiveness declines as tree size increases, however there were cases of successful burning of tall trees. Adequate fine fuel (usually, last year's dead grass) is necessary for satisfactory results. Safety also is a concern since many managers lack experience with fire and the equipment required to conduct fires.

The controlled use of fire is a large subject in itself. It is beyond the scope of this publication to provide detailed instruction on conducting prescribed fires. Two other Nebraska Extension publications provide information on the use of fire in general and on how to safely conduct fires. They are NebGuide G88 894, Grassland Management with Prescribed Burning, and Extension Circular 90 121, Conducting a Prescribed Burn. A fire plan should be prepared and a prescribed burning permit obtained from the local fire jurisdiction, as required by state law. Specialized fire equipment can be purchased. Two sources are the Ben Meadows Company, 3589 Broad St., Chamblee, GA 30341; and Forestry Suppliers, Inc, Box 8397, Jackson, MS 39284 8397.

Chemical Control

Herbicides are another tool in the integrated management program. Depending on the application method and chemical type, the use of herbicides can be time consuming and expensive, especially when used on denser tree infestations or large tracts of land. Effectiveness also is variable, depending on the tree size and label directions and/or restrictions. Always read and follow herbicide label directions. Herbicide information on control of troublesome plant species, including eastern cedar, is updated annually in the Guide for Weed Management in Nebraska (EC-130) In general, herbicides for eastern redcedar control can be used for broadcast application or individual-tree spraying.

Broadcast Treatments

Broadcast application is the most common method of applying herbicides in agricultural settings. The key message for the efficacy of broadcast treatments in eastern redcedar control is: "the shorter the tree the better control."

Since tree height was the most important factor influencing the level of chemical control (tree injury) with broadcast treatments, the herbicide efficacy data from Nebraska study was categorized by tree height . Recommended herbicides for trees that are up to two feet tall include: Surmount, Grazon P&D and Tordon. However, the same herbicides will not provide satisfactory control of trees taller than 2 ft, indicating the importance of tree heigh. Surmount at the rate of 5pts/acre can also cause short-term grass injury in the form of leaf yellowing and top growth burning. Cost of Grazon P+D and Tordon 22 K for broadcast applications can range from $21-$26 per acre. Since Surmount is not marketed product yet, its costs is not known.

Individual-tree Treatments

Individual-tree treatments can be applied directly to the tree foliage or to the soil around tree base. Soil treatments can minimize the amount of herbicide used and the exposure to non target species. However, soil treatments may not be effective unless applied before rainfall, preferably in Spring or Fall. Rain water is needed to move the herbicide into the root zone allowing an easier uptake by a tree. Recommended herbicides for soil application around tree base include Tordon 22K at the rate of 1 cc (ml) per every foot of tree height, Velpar-L at 4 (cc) ml and Spike 20P at 1cc (ml) per every inch of tree diameter. Cost of Tordon is about $85 per gallon, Velpar is about $65 per gallon and Spike 20P is about $9 per pound of product.

Individual-tree foliage can be also treated with various herbicides. Based on a study conducted in northeastern Nebraska, recommended herbicides for control of 2-10 feet tall trees include Surmount at 1.5 % volume per volume (v/v), Grazon P+D at 2.0% (v/v) and Tordon 22K at 1.0% v/v .

To help you determine volume per volume basis, for example, the 1% v/v equals 1 gall of product per 100 gallon of water. For smaller back pack sprayers use an equivalent of 1.3 oz of product per every gallon of water. Apply about 1.5 oz of the herbicide spray solution per every foot of tree height. Walk around the tree and just spray enough solution just to get a glisten (shine) on the canopy surface. Solution dripping off the canopy indicates a rate that is too high, and a likely waste of time and money. As an example, it was calculated that 1 gallon of spray solution could cover 15 individual trees that are 6 feet tall at a pressure of 20 PSI and a single nozzle type XR8002.

Grass injury in the form of temporary yellowing and burning of top growth was evident among all treatments especially for Tordon 22K. Roundup is not recommended for use in pasture settings due to poor activity on cedar trees and high injury level to the grass (Table 2). Cost of Grazon P+D and Tordon 22 K can ranged from $11-$16 per acre.

Practical Hint for Chemical Control

Use of selective herbicide treatments should be based on a tree height. Broadcast treatments are effective only on short trees (up to 2-ft tall), while the medium height trees (2 to 10 ft) can be controlled with individual-tree treatments. For broadcast treatments use 6-8 pints of Grazon P&D or 4-5pts of Surmount in a 20 gallon of water per acre. To prepare 1 gall of spray solution for individual-tree canopy treatments use 1.3 oz of Tordon, or 2.6 oz of Grazon P&D, or 2oz of Surmount. For larger spray tanks adjust herbicide rates accordingly.

Stevan Knezevic
Extension Weeds Specialist