Historic, Archive Document Do not assume content reflects current scientific knowledge, policies, or practices. aQK495 . Z9 U.S. Department of Agriculture F54 National Agricultural Library 2016 United States Department of Agriculture AUG 3 0 201? Received Acquisitions and Metadata Branch Field Guide for Managing African Rue in the Southwest Forest Southwestern Service Region TP-R3-16-15 Revised July 2016 United States Department of Agriculture rvCVf National Agricultural j[ Library Advancing Access to Global Information for Agriculture Cover Photos Top left: G.A. Cooper, USDA-PLANTS Database, Bugysood.org Bottom left: G.A. Cooper, USDA-PLANTS Database, Bugwood.org Right: Joseph M. DiTomaso, University of California-Davis, Bugwood.org In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating based on race, color, national origin, religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital status, family/parental status, income derived from a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all bases apply to all programs). Remedies and complaint filing deadlines vary by program or incident. 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Submit your completed form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: program. intake@usda .gov. USDA is an equal opportunity provider, employer and lender. Printed on recycled paper African TUG (Peganum harmala) Caltrop family (Zygophyllaceae) African rue is listed as a noxious weed in both Arizonaand Ecology New Mexico. This field guide serves as the U.S. Forest Impacts/Threats Service’s recommendations for management of African rue This weed is extremely toxic to cattle, sheep, horses, and in forests, woodlands, and rangelands associated with the humans; it contains at least four poisonous alkaloids. The Service’s Southwestern Region. The Southwestern Region seeds and fruit are the most toxic, followed by young covers Arizona and New Mexico, which together have 11 leaves and mature leaves. Animals typically avoid eating national forests. The Region also administers 4 national African rue because of its bad taste and smell. Most parts grasslands that are located in northeastern New Mexico, of the plant contain allelopathic chemicals that reduce the western Oklahoma and the Texas panhandle. growth of surrounding native plants. Description Site/Location Common in disturbed and barren areas such as roadsides, African rue (synonyms: wild rue, rue weed, Syrian rue, parking lots, oil pads, corrals, stockyards, open fields, harmal, esfand, ozallaik, ruin weed) is a succulent abandoned crop fields, river banks, ditches and arid/semi- perennial herb with a deep growing and robust root system arid desert areas, especially in moist soils. It can grow in that is a major obstacle to plant control. many soil types, including alkaline or highly saline soils. Growth Characteristics African rue is found throughout most western states, • Perennial bushy herb that grows 1 to 1.5 feet tall and including New Mexico, Arizona, Texas, California, 3-4 feet in diameter. Montana, Nevada, Oregon, and Washington. In New • Has a hardy woody taproot that reaches 25 feet or Mexico, it is primarily in southern counties with isolated more downwards into the soil profile. Creeping, populations found in central and northwestern counties. It lateral roots are produced about 12-15 inches below is common in eastern Arizona and western Texas. the surface that can extend up to 20 feet away from Spread the parent plant. Seeds and root fragments are readily transported by • Bright green leaves are alternate, smooth and divided running water. Seeds can be carried in mud that sticks to deeply into narrow lobes. Leaves have a very vehicles, railcars, and earth-moving equipment; thus, new disagreeable odor when crushed. plants easily spread along transportation corridors. Seed may also adhere to the feet, fur, or feathers of animals. • Single flowers are borne along the stem and in the Seed longevity is unknown but is probably persistent. forks of leaves. Flowers have five white petals and produce a green, orange, or brown-colored Invasive Features cylindrical seed pod (2-4 celled) with 45-60 seeds. African rue undergoes robust and rapid vegetative growth when soil moisture is available. It favors disturbed areas • Reproduces by seed, but new shoots and plants are such as those impacted by earth-moving equipment, also produced from adventitious buds along lateral excessive grazing, or vehicle use. Disturbed areas with roots. Seed is secured in a leathery fruit capsule; each moist soil such as roadsides, river or stream banks, riparian plant may produce as many as 1,000 capsules. corridors, waterways, and drainage or irrigation ditches are especially susceptible. This invasive weed is extremely drought tolerant and methods may increase effectiveness. In addition, more than exhibits “drought evader” growth characteristics. In one control method may be needed for each site. southern New Mexico, plants die back to their roots during Physical Control winter and initiate new annual growth in mid-to-late March. After spring growth and flowering, it may become Given African rue’s complex root system, it is extremely senescent (old-looking) and die back to the woody base as difficult to control the plant with only mechanical soils dry in summer. With cooler temperatures and techniques. The more practical and economical way to additional moisture coming later in the season, plants obtain effective long-term control is to use herbicide usually undergoes a second vegetative growth phase that treatments alone or in combination with a physical method. lasts until freeze occurs in early November. Manual Methods Hand-pulling, digging, or hoeing for control of mature Management plants is virtually impossible due to the depth of the root Because of African rue’s complex root system, methods to system. Hand removal of seedlings and young plants that is control the plant by means other than herbicidal application continued year after year may eventually control individual are quite limited. The plant grows back quickly after plants, but this approach is tedious and usually impractical. mowing or burning, and deep cultivation only fragments Mechanical Methods and spreads the roots. Grazing is also not an option due to Controlling African rue by plowing or grubbing individual toxicity, and there are no known classic biocontrol agents plants is ineffective since the roots are too deep to dig out at this time. Since African rue is able to regenerate from and any root parts left in the ground will likely re-sprout. In root fragments, grubbing or cultivation may actually many instances, cultivation may actually lead to an increase increase the population size. in population size. In certain agronomic situations, repeated The following actions should be considered to contain and deep cultivation combined with reseeding perennial plants reduce African rue populations: has been found to be somewhat successful; but this is an expensive option. Mowing or blading also causes the plant • Maintain healthy plant communities to prevent or to re-sprout and spread. limit infestations of African rue. Prescribed Fire • Detect and eradicate new populations of African rue as early as possible, especially along roadways, Fire is not an effective control method as plants grow back waterways, and ditches. rapidly after burning. • Use foliar or soil-active herbicides at recommended Cultural Control rates for effective control of African rue populations. Early detection and plant removal, especially for seedlings Application methods include broadcast or individual and young plants, are critical for preventing African rue plant treatment (IPT). establishment and spread. Land managers, road crews, and Table 1 below summarizes some management options for the local public should be educated on identification so common situations involving African rue. Further details they can report suspected populations. Vehicles, humans, on these management options are explained below. Choice and livestock should be discouraged from traveling through of control method(s) for African rue depends on the land infested areas; a program to check and remove seeds from use and current site conditions (accessibility, terrain, soil vehicles and livestock after going through infested areas and air temperature, weather, extent and density of should be implemented to help stop the spread. Hay. straw infestations, other flora and fauna present, etc.). Other mulch, planting seeds, fill, and other related materials considerations include treatment effectiveness, cost, and the should be certified to be weed free before use in areas time needed to achieve control. Combining control undergoing treatment. 2 Table 1. Management options* Site Physical Control Cultural Control Biological Control Chemical Control Roadsides Few options available. Use seed, mulch, and fill None known at this time. Use truck or tractor spraying materials certified to be equipment. Wash underneath to Combine suppression weed-free. prevent spread. methods (e.g., repeat deep cultivation or Limit disturbances along mowing) with reseeding roadsides. desired native perennial Implement requirements for plants. vehicle operations and for reporting infestations along roads. Ditches and Few options available. Limit disturbances along Same as above. Use herbicide with approved waterways waterways and ditches. aquatic labeling when near or in Hand extraction or water. hoeing can be used to Increase public awareness target seedlings. and reporting of plant presence along ditches and roadways. Rangeland Few options available. Use seed and forage hay Same as above. Use ground broadcast spraying certified to be weed-free; use with ATV or tractor; however, pellets for horses in backpack spraying may be more backcountry areas. practical in areas with difficult access. When moving livestock or vehicles through infested Consider individual plant treatment areas, inspect mud on in areas with less dense infestation animals, clothing, and or near desirable vegetation. vehicles and remove any seeds before entering un¬ infested areas. Wilderness Few options available. Use seed and forage hay Same as above. Use backpack sprayers for and other certified to be weed-free; use individual plant treatment or Hand removal repeated natural areas pellets for horses in ground broadcast spraying with an year after year may be backcountry areas. ATV or tractor, if allowed. required for effective control. Post signs warning visitors to remove seeds. * Choice of a particular management option must be in compliance with existing regulations for the land resource. Biological Control Classical Biological Control Grazing There are no known classical biocontrol agents (insects, pathogens, etc.) available for African rue at this time. Grazing is not a viable option for removing African rue. Due to its bad taste and smell, livestock usually avoid the Chemical Control plant unless other forages are unavailable. However, Numerous herbicides have been investigated in African rue has occasionally been found in hay bales. university-led field trials for African rue control. These Effects of poisoning on livestock include loss of appetite, tests show that only chemicals translocated deep into the trembling, and loss of coordination. Severe poisoning can plant’s root system can effectively kill the weed (see table result in hemorrhaging in the heart and liver. 2). Certain selective, systemic herbicides (e.g., metsulfuron) will suppress seasonal top growth; however, 3 most plants recover and regrow within a year of treatment. spraying, but some damage should still be expected. Unfortunately, the few herbicides that provide effective • Time needed to gain control is slow, requiring a long-term control (e.g., imazapyr, tebuthiuron, and year or more to kill a plant when either sprayed hexazinone) are nonselective and may cause unacceptable foliarly or treated with a soil-active herbicide. injury to desirable species, especially grasses. Herbicide Application Options It is very important to read the herbicide label carefully Broadcast foliar spray treatment - The ideal time to and follow all instructions when mixing and applying any spray African rue foliarly varies from year to year because herbicide. Equipment used to spray herbicide should be of specific weather conditions. Expect average to above- calibrated. Aquatically approved formulations should be average winter moisture to produce a prolific burst of new used in or near water. When using aquatic herbicide vegetation growth in spring, which is needed before formulations, an aquatically approved surfactant should spraying to maximize chemical uptake and movement also be added to the spray mix (translocation) through all portions of the plant. In General Considerations for Control droughty years, African rue will have poor foliage and Based on research and practical experience, the following flower growth; therefore, spraying is not recommended. guidelines should be used for herbicidal control of Similarly, healthy foliage that results from above-average African rue: summer rainfall can be sprayed late in the season. At the time of spraying, soil temperature at a 6-inch depth • Plant condition and growth stage at the time of should be between 55 °F and 70 °F. In years with average application are critical for control success. When to above-average winter precipitation, the desired growth using a foliar spray, treating African rue that is stage and soil temperature range occurs roughly from healthy and robust in late summer (September- April 1 to May 15, plus or minus 15 days. In late season, October) is optimal. Plants in the early vegetative the desired growth stage is usually from September 1 to and bloom stage in spring (April) can also be October 1. successfully controlled provided soil moisture is adequate. Do not spray African rue that has been Using imazapyr alone or in combination with other stressed from drought, disease, insects, or other herbicides has consistently provided the best African rue causes that might have resulted in dieback, control. Imazapyr (e.g.. Arsenal®) is very active on the yellowing, or other plant damage. root system and is the most common commercial product used for African rue control. Imazapyr is labeled for • Weather conditions at the time of spraying are pasture/rangeland, noncropland sites, rights-of-way, important to successful herbicide activity. Coverage industrial areas, fence rows, non-irrigation ditch banks, is best with low wind speeds (3 to 8 mph) and cool establishment and maintenance of w ildlife openings, and temperatures (between 50 °F and 85 °F). Air for bare ground weed control. When broadcast spraying temperatures above 85 °F increase spray solution larger infestations, use a 1.75 lbs. a.i. per acre rate, which volatility and thus reduce herbicide available to be is equivalent to 3 pints of product per acre. When spot absorbed by the plant. Do not spray a foliar-active treating smaller populations or isolated plants, use an 1PT herbicide if a rainstorm is expected within 6 hours of approach as described below. A surfactant should be application. added to the herbicide mixture at rates specified on the • The plant community associated with the African herbicide label. Imazapyr is a nonselective herbicide so rue population should be closely evaluated before damage to grasses and other associated plants should be treating an area. Use of a nonselective herbicide anticipated. should not be made in areas where grass A new herbicide product called Viewpoint® (active preservation is desired. Individual plant spraying ingredients: aminocyclopyrachlor + imazapyr + will minimize grass damage relative to broadcast 4 Table 2. Herbicide recommendations Spot Common Broadcast Treatment Chemical Name Product Treatment (spray Time of Application Remarks (active Example(s)1 (rate per solution and ingredient) acre) pellets)2 Imazapyr Arsenal 3 pints per acre 3% Spray healthy Imazapyr is a nonselective Habitat regrowth foliage in herbicide: anticipate damage [others good condition in late to non-target plants from available] summer or early fall. overspray, runoff, movement in soil, or root exudates. When performing 1PT with a backpack sprayer, adjust nozzle to wet foliage thoroughly. Aminocyclopyrachlor Viewpoint 3-18 ounces NA Same as above. This herbicide combination + metsulfuron + per acre provides nonselective imazapyr control and should only be used in non-crop areas. Metsulfuron Escort 3.2-6.4 ounces NA Same as above. Metsulfuron is selective and Ally per acre provides seasonal foliage suppression but low mortality in African rue. Tebuthiuron Spike 20P 10-15 pounds NA Anytime but optimal Apply only on sandy or of pellets time is just before a coarse soils; will likely rain event. damage associated vegetation. Hexazinone Velpar NA Mix 50:50 with Anytime. To apply as an IPT. squirt water in a 4 ml of mixture on the soil backpack surface next to each plant. sprayer. Apply 4 Not recommended as a ml per plant broadcast because it is (equivalent to 2 nonselective and will ml undiluted damage or kill associated Velpar). vegetation. 1 Trade names for products are provided for example purposes only, and other products with the same active ingredient(s) may be available. Individual product labels should be examined for specific information and appropriate use with African rue. 2 Spray solution is the herbicide/water ratio in a spray mix that may be used for spot treatment with backpack or hand-held sprayers. The amount of product applied during an annual growing season must not exceed the maximum application rate per acre as specified by the product label - refer to the product label for the site type and application. metsulfuron) provides good to excellent control of African the herbicide label carefully for use directions. rue when applied at a rate of 13 to 18 ounces of product Broadcast soil-active treatment - African rue growing on per acre. Viewpoint is formulated as a dispersible granule rangeland with sandy to loamy soils may be controlled that is mixed in water and applied as a liquid spray. This with a broadcast rate of tebuthiuron (e.g.. Spike 20P®) herbicide is labeled specifically for non-crop situations applied at 2 to 3 lbs. a.i. per acre. Unlike the liquid foliar- only, such as spraying rights-of-way, oil pads, parking lots, active herbicides, tebuthiuron is a dry pellet formulation etc. It provides broad-spectrum control of brush and weeds that is applied to the soil surface. These pellets remain species. Care should be exercised when using this product intact until they are dissolved by rainfall and the chemical in the vicinity of crops or other desirable plants because is moved into the soil where it is taken up by roots. this herbicide combination may injure or kill them. Read 5 Tebuthiuron is appliedby aerial or ground methods and unique and requires site-specific management decisions. In provides fair to good African rue control. However, damage most cases, effective control of African rue requires to associated vegetation should always be anticipated at the herbicide spraying. Depending on the intended land use relatively high rate of application required. and available budget, consider reseeding desired plant communities, as healthy plant populations can deter spread Individual plant treatment (IPT) - IPT is an effective way of African rue. to control the plant; however, the method is often time- consuming and costly, especially ifthe African rue is dense. Even with herbicide use, it may take years to reduce the For practical reasons, IPT is ordinarily used only for small presence of this plant, which can regenerate from deep¬ areas where African rue is growing sparsely and the growing root parts as well as seed. Since it is ordinarily population is easy to treat. Two active ingredients, hexazinone useless to treat an area only one time without retreatment, and imazapyr, are preferred IPT choices, but they are applied sufficient resources must be allocated for the area where in different ways as described below; control is attempted. After initial treatment, it is important that resources should also be available to respray or retreat • Hexazinone (e.g., Velpar®) can be applied as a liquid the treated area as necessary. Always anticipate the need directly to the soil surface next to the canopy of for monitoring and additional control measures such as individually treated plants. For IPT, hexazinone spot spraying with a backpack or hand-held sprayer. should be diluted as a 50:50 mix with water in a backpack sprayer. A quick squirt of the handle with References and Further the nozzle turned to a straight stream generally Information administers about 4 ml of solution (or 2 ml of active product), which is the desired rate of application. Abbot, L.B, D. Lepak, and D.L. Daniel. 2007. Vegetative Before spraying, check the handle pressure and and Reproductive Phenology of African rue in the practice with water in the sprayer to calibrate this Northern Chihuahuan Desert. The Southwestern delivery rate. Adding a blue dye to the spray mixture Naturalist 52(2):209-218. helps to identify treated plants. Hexazinone moves Duncan. K., K. McDaniel, and M. Renz. 2005. Chemical into the soil profile with rain and is taken up by Weed and Brush Control for New Mexico roots. Thus, application prior to anticipated rainfall is Rangelands. Las Cruces: New Mexico State Univ. preferred, but the product usually works at any time College of Agriculture and Home Economics and of year. Cooperative Extension Service. Pp. 6. Available at • Imazapyr diluted as a 3 percent mixture with water is http://aces.nmsu.edu/pubs/_circulars/CR 597.pdf. effective for IPT. Most herbicide activity is through Fact Sheet: Stop the Spread of African Rue. November the foliage so use a backpack sprayer with its nozzle 2009. Published by the Government of South adjusted to wet the top growth of individual plants Australia/South Australian Arid Lands Natural completely. Add blue dye to the spray mixture to Resources. Available at http://www.saalnrm. help view spray coverage and to identify treated sa.gov.au/ (accessed Sept. 2014) plants. Hart, C.R. 2002. African rue - Biology and Management. Management Strategies University of Texas A&M Publication L-5429 10- 02. Available at http://pecosbasin.tamu.edu/ Early detection and control of new African rue populations, media/2652/L-5429.pdf (accessed Sept. 2014) especially near waterways and ditches, are important to slow the spread of this noxious weed. Once established, La Plata County Weed Office, 2500 Main Avenue, African rue is difficult to eradicate without also impacting Durango, CO. Available at www.lpcweeds.org/ associated desirable plants. Each treatment situation is Africanrue.htm (accessed Sept. 2014) 6