COOPERATIVE EXTENSION SERVICE UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE, FOOD AND ENVIRONMENT, LEXINGTON, KY, 40546 ID-52 What’s Wrong With My Taxus? Cheryl A. Kaiser and Nicole A. Ward Gauthier, Plant Pathology, Lee H. Townsend, Entomology, and Richard E. Durham, Horticulture

axus (yew) is an evergreen shrub Recommendation: commonly found in Kentucky • Foliar sprays in May and June will landscapes.T Numerous conditions can kill black vine weevils and ultimately cause these shrubs to exhibit yellowing may help to reduce root damage by and browning symptoms. While diseases larvae. (Figure 1) and insect pests (Figures 2, 3, • Some insecticides are labeled for and 4) can result in damage, Taxus trou- drench application around the base bles are often the result of adverse grow- of Taxus to kill larvae in the soil ing conditions. Pinpointing the specific from late summer through early cause requires a thorough examination autumn. of the affected shrub, an investigation of • Contact your county Extension of- the surrounding area, and knowledge of fice for current information on man- possible stress factors. agement of the black vine weevil. The following questions and supple- Do buds fail to grow in the spring? mentary information are meant to assist homeowners and consultants in Occasionally, Taxus bud mites can determining the cause of Taxus decline. damage or kill buds. Needles and shoots Answering “yes” to one or more of these may also become distorted. These mites questions should suggest a possible cause are small, so proper identification can be to the shrub’s troubles. difficult. Figure 1. Needle dieback resulting from root Recommendation: loss. Phytophthora root rot (shown here) and The Affected Shrub “wet feet” can both cause similar symptoms • Applications of a mite-control prod- as a result of root damage. uct in May and again in mid- to late Are there any apparent wounds June may provide some control. or broken branches? Are there any cankers? Examine the shrub for evidence of Are needles covered with a Look for dead, sunken areas on twigs wounds due to physical injury. Types of sooty black deposit? and branches that show yellowing and injuries include: Sooty molds are black-colored fungi dieback. Several fungi (e.g. Pestalotia, • Bark torn or cut away from twigs, that develop on the sticky secretions Phyllostictina, Physalospora, and Sphae- branches, or trunks (honeydew) left by certain sucking ropsis) can cause cankers that girdle • Partially broken branches insects. The sooty mold fungus is not branches. • Nursery tag wires or strings that pathogenic, but its growth shades needles Recommendation: were not removed and may reduce photosynthesis. Infesta- • Prune dead and broken branches. tions of sap-feeding insects will result in Bark torn from as little as one-third • Destroy branches that have cankers. yellowed, unthrifty foliage, poor growth, the circumference of a branch may and may cause branch or plant death. cause the branch to die from the wound Do needles appear to have been chewed? Insects that can leave honeydew de- upward to the growing tip. Similarly, The black vine weevil chews semi-cir- posits include: broken branches and nursery tags that cular holes or notches along the edges of • Cottony Taxus scale—usually found restrict growth can result in yellowing Taxus needles (Figure 2). Weevil feeding on underside of needles; crawlers are of needles. Death of affected branches on leaves is not a significant problem in active in June may eventually occur, although damage Kentucky; however, the legless grub-like • Fletcher scale—a stationary hemi- may not be evident until the following larvae may feed on roots. Root injury spherical brown insect about the summer. can cause needles to turn yellow, and size of half a BB shot (Figure 3); Recommendations: portions of the shrub may die. Contin- ued damage can lead to the death of the crawlers are active in mid-June • Prune dead and broken branches. • Taxus mealybug—tends to be found • Fertilize in late autumn. entire shrub. Black vine weevils can be accidental invaders in homes in autumn, in clusters in branch forks and along another indication of an infestation. stems and branches (Figure 4); there are several generations of this insect each year. Agriculture and Natural Resources • Family and Consumer Sciences • 4-H Youth Development • Community and Economic Development EXTENSION Courtesy of Missouri Botanical Garden

Figure 2. Black vine weevil feeding causes Figure 3. Fletcher scale adults are flat, oval, Figure 4. Taxus mealybug cluster in branch notches in needles. stationary brown insects. forks and along stems.

Recommendations: Recommendations: • Irrigate shrubs not receiving 1 inch • Sap-feeding insects often thrive on • Avoid planting Taxus on sites that to 2 inches of rainfall per week. stressed plants. Follow a good fertil- are exposed to drying winter winds. Shrubs should be watered at least ity and watering regime to promote • Water as needed until the ground until they become well established plant health. Do not over-fertilize. freezes. (about two to three years). • Remove heavily infested branches. Is the browning confined to the • Protect new growth with insecti- tips of individual branches? The Growing Site cide sprays applied to the crawler or Does the soil remain wet for long periods? nymphal stages of the insects. Browning on tips of individual branch- es can occur when tender new growth is Does water from a downspout Is only the interior foliage affected? “nipped” by a late spring frost (Figure 5). flow near the shrub? Browning of interior needles (older Damage will be evident shortly after the Taxus is sensitive to excessive soil growth) while tips (new growth) remain frost event. Plants usually recover from moisture; affected plants wilt, yellow, green may be due to a couple of issues. In this problem. and turn brown over a period of several late summer or early autumn, all three- to months. Brown, dead roots will be pres- Has the shrub been transplanted recently? five-year-old needles may suddenly turn ent in the lower portion of the root ball, yellow throughout interiors of shrubs. Newly planted trees and shrubs be- while a few white living roots may be Needles remain on shrubs for several come stressed as a result of being moved evident nearest to the soil surface. Bark weeks before they fall. This is normal from one environment (production site) decays and readily sloughs off deeper needle senescence (drop) and should not to another (landscape). Shrubs that die a roots. This condition, known as “wet feet,” cause concern. year or two after transplanting may have can result from any of the following situ- Browning and death of one-year-old succumbed to transplant shock. Follow- ations: or older foliage may also be due to win- ing transplanting procedures outlined in • Poorly drained soils ter injury. Symptoms become evident the publication, Transplanting Trees and • Planted in a low area on older needles in spring, while new Shrubs (ID-80), can help minimize this • Planted near a downspout in which growth is unaffected. This condition -oc stress. water drains into the root zone curs during windy days in winter when Recommendations: • Overwatering the ground is frozen. Because moisture • Purchase plants from a reputable Excessive soil moisture also can cannot be replenished rapidly enough, landscape business. provide conditions favoring root decay needles become dry. Damage may occur • Do not place the plant any deeper pathogens, which further damage Taxus mainly on portions of shrubs exposed to in the soil than its original grow- roots. One such disease is Phytophthora prevailing winds. ing depth in the nursery. Check the root rot (Figure 1). Foliar symptoms may color of the bark to know this depth.

2 not be evident until the following sum- mer when temperatures begin to rise and root mass is not sufficient enough to sustain plants. Recommendations: • Avoid planting Taxus in poorly drained soils. • Amend clay soils with organic mat- ter to help improve drainage prior to planting. • Raise beds at least 8 inches. • French drains may be installed to divert excess water. • Redirect downspouts or use extend- ers so rainwater does not drain into the plant’s root zone. Are there acid-loving plants growing nearby? Figure 5. Late spring frosts can damage newly emerging shoots. Taxus grows best at a soil pH in the range of 6.0 to 6.5. Plants that prefer rooting that makes plants more suscep- an acid soil pH (e.g. 4.5 to 5.5) are con- tible to drought conditions. sidered “acid-loving.” Problems occur Recommendation: when Taxus is planted near acid-loving • Provide sufficient water as needed ornamentals, such as andromeda, azalea, throughout the growing season, laurel, and rhododendron. Fertilizers pre- until the ground freezes. pared specifically for this group of plants • Avoid using landscape fabric around tend to make the soil more acidic. This woody trees and shrubs. Instead, may cause nearby Taxus shrubs to turn apply a 1- to 2-inch layer of organic yellow and die over a period of several mulch, such as bark or hardwood months. chips. Recommendations: • Avoid planting Taxus in the same plant bed as acid-loving ornamen- Other Possible Stresses Has there been any construction tals. or digging activity nearby? • Soil should be tested every two to three years to determine whether Construction activities, including pH is in the correct range. Contact digging holes or ditches, within several feet of the shrub may damage roots that Figure 6. Herbicides often cause needle dis- your local Extension office for infor- tortion and downward curling. mation on proper collection of soil supply water and nutrients to plants. for analysis. Construction may also compact soil around plants, which may interfere with • Adjust soil pH, if necessary, per soil- Have herbicides been used nearby? the ability of the soil to supply needed test result recommendations. The use of lawn weed killers (herbi- water and oxygen to root systems. Injured cides) can have a detrimental effect on Has the shrub been stressed plants yellow, wilt, and can eventually nearby shrubs when chemicals drift on during dry periods? die. Tunnels dug through root zones by windy days or when granular herbicides Prolonged drought can result in symp- chipmunks or moles may also damage move into root zones through runoff. toms similar to those caused by excess roots sufficiently to cause decline. Plants that come into contact with her- water (wet feet). During dry weather, clay Recommendations: soils may pull away from roots, causing bicides may take up active ingredients • Avoid disturbing soil around the through leaves or roots. Symptoms fine fibrous roots to dry out and die. root zone of plants. Drought stress can also occur where soils caused by exposure to growth regulator • Protect soil from compaction by ex- herbicides (e.g. 2,4-D or Dicamba) in- dry rapidly or where roots are located cluding heavy equipment and excess near the soil surface. The use of landscape clude twisting, distortion, or downward traffic. Foot traffic (humans or pets) curling of needles (Figure 6). fabric on the soil surface around woody also compacts soils. trees and shrubs encourages shallow 3 Recommendations: • Do not apply herbicides on windy days or where they could be ab- sorbed by Taxus roots. • Some lawn fertilizers also contain herbicides; check labels before apply- ing near Taxus or other landscape plants. Have de-icing salts been used nearby? De-icing salts applied to sidewalks and streets during winter can injure Taxus when products wash into the ground. Symptoms may not be apparent until plant growth begins in spring. Browning of needles is usually most evident on sides of the shrubs nearest to salt applications (Figure 7). Recommendations:

• Water soil for several hours to leach Figure 7. Salt injury often occurs on lower branches that face salt applications, such as side- out accumulated salts. walks. • As an alternative to salt, use sand to increase traction on sidewalks near Photo credits: Taxus. Additional Resources John Hartman, UK Plant Pathology: • Plant-safe commercial de-icing Planting Balled and Burlapped Trees Figures 1, 5, 6 substitutes are available. Read labels Missouri Botanical Garden: Figure 2 and Shrubs in Your Landscape, ID John Weidhass, VPI, Bugwood.org: Figure 3 before use. 91 (University of Kentucky): http:// Hannah Nendick-Mason: Figure 4 www.ca.uky.edu/agc/pubs/ho/ho91/ Joseph LaForest, University of Georgia, Do dogs frequently urinate Bugwood.org: Figure 7 ho91.pdf. on the affected shrub? Taxus Scales, ENTFACT-434 (Univer- Yellow or brown areas confined to sity of Kentucky): http://www.ca.uky. the lower branches of Taxus may be due edu/entomology/entfacts/ef434.asp. to dog urine injury. Damage generally Transplanting Trees and Shrubs, ID-80 occurs in a single area at base of shrubs. (University of Kentucky): http:// Has soil been added as a fill www.ca.uky.edu/agc/pubs/id/id80/ around the shrub? id80.htm. The addition of soil on top of the ground prevents roots from receiving adequate supplies of oxygen. As little as 2 inches of soil added on top of root systems may be detrimental to the health of shrubs. However, a 1- to 2-inch layer of mulch is not harmful and may provide beneficial effects to the plant while add- ing perceived depth to the soil.

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Revised 6-2013