North Dakota Tree Handbook

Woody Plant Pests

There are many woody plant pests that can be a problem on trees within large areas throughout the Northern Great Plains. The type of pest and its population size will vary with a particular season and from hot/dry periods to cool/wet periods. This section of the North Dakota Tree Handbook is intended to inform the reader of common problems associated with trees. It is important to remember that trees rarely succumb to a single pest problem. Trees often die because of a combination of biotic and abiotic factors that have affected them over a period of years. (See Figure 4-5. Decline/Pest Spiral).

Figure 4-5. Decline/pest spiral.

Manion, Paul D., TREE DISEASE CONCEPTS, 2/EŠ 1991, p.333. Reprinted by permission of Prentice-Hall, Inc., Englewood Cliffs, N.J.

The vigor and defenses of the tree are reduced when attacked annually by such factors as soil compaction, poor fertility, physical injury, drought, etc. As tree health declines, the defenses are further weakened and the door is opened for the entrance of various insect and disease pests. Weakened trees can be restored to an improved health condition by watering, fertilization, pest control, etc., where practical.

This section is organized in the following sequence:

  1. List of Annotated References on Tree Pests - Current references on identification, injury symptoms and control/management of tree pests are listed.
  2. Diagnosing Tree Problems Using Injury Symptoms - A key to identification of pest problems by injuries to woody plants is presented. This key is quite useful if you have minimal training in entomology/plant pathology. Reference codes correspond to those cited in the list of Annotated References.
  3. Reference Sections on Three Major Pest Groups: Insects, Diseases and Abiotic Pests - A brief overview of the pest, its recent severity and occurrence across North Dakota.
  4. List of Common and Scientific Names of Woody Plant Pests - A cross reference of various woody plant pests in North Dakota.

List of Annotated References on Tree Pests

  1. "Insects That Feed on Trees and Shrubs"

    Johnson, Warren T. and Howard H. Lyon

    1988. Comstock Publishing, a Division of Cornell University Press, ISBN 0-8014-0956-X, 556 pp., 241 color plates.

    Note: This book and its companion volume "Diseases of Trees and Shrubs," (see reference 2), should be in every reference collection. Color plates of the damage and all important life stages make these references easy to use for even the layman. Information in both volumes is arranged not as a taxonomic guide, but as a field guide. Both volumes are in print and readily available. More than 650 species of insects that can damage over 200 species of woody plants are covered.

  2. "Diseases of Trees and Shrubs"

    Sinclair, Wayne A., Howard H. Lyon, and Warren Johnson

    1987. Comstock Publishing, a Division of Cornell University Press, ISBN 0-8014-1517-9, 575 pp., 247 color plates.

    Note: (see reference 1) The color plates contain more than 1700 illustrations of the diseases and injuries that some 350 biological agents and environmental factors cause to more than 250 species of plants.

  3. "Common Insect Pests of Trees in the Great Plains"

    Dix, Mary Ellen, Judith Pasek, Mark Harrell, and Frederick P. Baxendale, Technical Coordinators.

    1986. Great Plains Agricultural Council Publication No. 119, Nebraska Cooperative Extension Service EC 86-1548 (Cooperative effort of USDA Forest Service, Rocky Mountain Forest and Range Experiment Station and University of Nebraska Cooperative Extension Service, 44 pp.

    Note: This publication was developed by entomologists on the GPAC Pest Management Task Force and is highly relevant to North Dakota. It is designed for those with no formal training in entomology. There was a general distribution to Soil Conservation Service and Extension offices. This reference is still available through Nebraska Extension Service.

  4. "Diseases of Trees in the Great Plains"

    Riffle, Jerry W. and Glenn W. Peterson, Technical Coordinators

    1986. Gen. Tech. Rep. RM-129. Fort Collins, Co: USDA, Forest Service, Rocky Mountain Forest and Range Experiment Station, 149 pp.

    Note: This reference covers 46 hardwood and 15 conifer diseases present in the Great Plains and is one of the most valuable texts on diseases present in North Dakota.
  5. "Tree and Shrub Insects of the Prairie Provinces"

    Ives, W.G.H., and H.R. Wong

    1988. Canadian Forestry Service, Northern Forestry Center, Edmonton, Alberta. Information Report NOR-X-292, 327 pp.

    Note: More than 600 species of insects and mites that feed on trees and shrubs in the prairie provinces are discussed in terms of their damage, life cycle, distribution and appearance. There are approximately 1100 color photographs. A valuable reference for North Dakota.

  6. "Forest Tree Diseases of the Prairie Provinces"

    Hiratsuka, Y.

    1987. Canadian Forestry Service, Northern Forestry Center, Edmonton, Alberta. Information Report NOR-X-286, 142 pp.

    Note: The major forest tree diseases of the prairie provinces are described in terms of their cause, distribution and hosts. Twenty-five coniferous and 15 deciduous diseases are illustrated by color photographs. A very good reference.
  7. "A Guide to Insect, Disease and Animal Pests of Poplars"

    Ostry, Michael E., Louis Wilson, Harold S. McNabb Jr., Lincoln M. Moore

    1989. USDA Forest Service, Agricultural Handbook 677. Washington, D.C., 118 pp.

    Note: Describes and illustrates with color photos, the major insects, diseases and animal pests of poplars. Provides information on the identification, biology and control of casual agents. Emphasizes field identification and provides references for further information.
  8. "Key to Shelterbelt Insects in the Northern Great Plains"

    Stein, John K. and Patrick C. Kennedy

    1972. USDA Forest Service, Research Paper RM-85, Rocky Mountain Forest and Range Experimental Station, Fort Collins, Colorado, 153 pp.

    Note: Contains a key to 227 insect pests. The key contains 235 photos, drawings and four tables which make this a valuable tool.
  9. "Field Guide to Disease and Insect Pests of Idaho and Montana Forests"

    Hagle, Susan K., Scott Tunnock, Kenneth Gibson, and Carma Gillagan

    1987. USDA Forest Service, State and Private Forestry, Northern Region. PO Box 7669, Missoula, Montana 59807, 123 pp.

    Note: Contains keys, color pictures and descriptions of conifer pests in the Northern Region. A valuable reference for conifer insects, diseases and abiotic conditions.
  10. "Christmas Tree Pest Manual"

    1983. USDA Forest Service, North Central Forest Experimental Station, St. Paul, MN, 108 pp.

    Note: Color photographs and descriptions of 70 Christmas tree pests will help growers and others to identify the causes of various tree injuries. Describes ways to prevent or reduce damage from insects, diseases, birds, mammals and environmental factors. Excellent conifer reference for the north central area.

  11. "Insects of Windbreaks and Related Plantings: Distribution, Importance, and Management."

    Dix, Mary and Mark Harrell, editors.

    1991. USDA Forest Service Rocky Mountain Experiment Station, General Technical Report RM-204, Fort Collins, Colorado, 50 pp.

    Note: Proceedings of several authors on the importance of pest control in windbreak and tree plantings, distribution of insects in windbreaks, influences in invertebrate ecology, sampling procedures, host susceptibility and managing pests in windbreak plantings.
  12. "Diseases of Trees and Shrubs: Color Diagnostic Guide"

    Ash, Cynthia, Martin Draper, H. Arthur Lamey and Dale Gallenberg

    1994. Minnesota Extension Service, University of Minnesota, St. Paul, Minnesota, NDSU Circular PP-1082, 12 pp.

    Note: Color pictures of disease pests, jointly produced by Extension Services are University of Minnesota, North Dakota State University and South Dakota State University.
  13. "Diseases Management Recommendations for Trees and Shrubs"

    Ash, Cynthia, Martin Draper, H. Arthur Lamey and Dale Gallenberg

    1995. Minnesota Extension Service, University of Minnesota, St. Paul, Minnesota, NDSU Circular PP-1100, 16 pp.

    Note: Symptoms and management recommendations for common tree disease pests of the northern plains. Jointly produced by the Extension Services at University of Minnesota, North Dakota State University and South Dakota State University.
  14. "Deciduous Tree Diseases"

    Stack, Robert and H. Arthur Lamey

    1995. NDSU Extension Service, North Dakota State University, Fargo, North Dakota, NDSU Circular PP-697 (Revised) 31 pp.

    Note: Reference of disease pests separated into three categories: widespread occurrence, specific hosts and non-parasitic disorders.

  15. "Disease Control in Cherries, Plums, and Other Stone Fruits"

    Lamey, H. Arthur and Robert Stack

    1991. NDSU Extension Service, North Dakota State University, Fargo, North Dakota, NDSU Circular PP-689 (Revised), ?? pp.

    Note: Description of diseases pests, management and control recommendations.

  16. "Diseases of Apples and Other Pome Fruits"

    Lamey, H. Arthur and Robert Stack

    1993. NDSU Extension Service, North Dakota State University, Fargo, North Dakota, NDSU Circular PP-454 (Revised), 12 pp.

    Note: Description of disease pests, management and control recommendations.
  17. "Insects Pests of Evergreens"

    McBride, Dean

    1988. NDSU Extension Service, North Dakota State University, Fargo, North Dakota, NDSU Circular E-297 (Revised), 2 pp.

    Note: Brief description and control recommendations for evergreen insect pests.

  18. "Common Insect Pests of Tree and Shrubs in North Dakota"

    Glogoza, Phillip

    1995. NDSU Extension Service, North Dakota State University, Fargo, North Dakota, NDSU Circular E-296 (Revised), 8 pp.

    Note: Brief description of insect feeding, damage, specific pest identification and control recommendations.
  19. "Weed Control in Tree Plantings"

    Quam, Vernon and Richard Zollinger

    1995. NDSU Extension Service, North Dakota State University, Fargo, North Dakota, NDSU Circular W-1097, 20 pp.

    Note: Various types of weed control are discussed including mechanical, use of mulches, cover crops, herbicide descriptions and use recommendations.

Diagnosing Tree Problems Using Injury Symptoms


By comparing injury symptoms to examples listed in this guide, it is possible to identify over 140 specific insect, disease or abiotic tree and shrub problems. Following the name of the damaging agent is a reference and page number. These letters and numbers refer to specific references on the Annotated Reference List on the previous three pages. For the "novice" this gives a name and a means of identification, for those more familiar with tree problems, this guide may serve as a checklist or as a reminder of less often encountered problems. The first step in control or problem evaluation is proper identification.

How to Use This Guide

This guide is broken down by injury to conifers or deciduous trees and shrubs.

Within each there are four major categories:

I. Injury to Foliage
II. Injury to Twigs or New Shoots
III. Injury to Trunks or Larger Branches
IV. Entire Tree Dying.

To identify a problem, determine the specific nature of the injuries and compare them with examples in the chart.

EXAMPLE: You notice that leaves are being eaten on your elm trees, and while examining the problem you disturb the foliage and caterpillars fall down and hang suspended on a silken thread.

To identify, go to:

I. Injury to Foliage

A. Leaves being eaten

3. No webbing, larvae hang from a thread when the foliage is disturbed
(cankerworms and associates).

Now you know the pest problem; go to the plant host and identify the specific pest name and further references.

                  woody plant pest name
Elms: spring cankerworms; R1-P142, R3-P1.
  \                                /   |
 host plant name                  /     |
                                 /   page number of reference #3
         reference number from _/
            previous section 


Although a large percentage of the commonly encountered problems are included, keep in mind there are many that could not be included and new ones continue to appear every year.

Table 4-9. Diagnostic key of conifer tree problems.

I. Injury to Needles

  1. Needles being eaten
  1. Webbing present, (bud cap often retained by silk)
    Spruce: spruce budworm; R1-P28, R5-15, R8-43, R17-P2. *
  2. No webbing Pine: introduced pine sawfly; R1-P16, R5-P35, R10-P42. European pine sawfly; R1-P16, R3-P12, R5-P35, R10-P39.
    Spruce: yellow headed spruce sawfly; R1-P18, R3-P13, R5-P33, R8-P26.
    tussock moth; R1-P26, R5-P18, R10-P44.
    Larch: larch sawfly; R5-P37, R8-P26.
  1. Needles damaged or missing, but not consumed, may be off color or have discolored spots or bands or be mined out
  1. Spruce needles fade to purplish or brownish and fall off, current years needles undamaged. Rhizosphaera needle cast; R2-P42, R4-P124, R12-P3, R13-P14.
  2. Pine needles fading to yellowish and developing brownish spots or bands, (second year or older needles) Cyclaneusma (Nemacyclus) needle cast; R2-P38, R4-P125, R10-P29.
  3. Needles with small waxy white spots
    Pines and spruce:
    pine needle scale; R1-P108, R3-P38, R5-P41, R8-131, R9-P85, R17-P2.
  4. Needles being mined out in the needle sheaths
    tip moths; R1-P48, R3-P22, R8-P96.
    pine needle sheath miner; R1-P38, R3-P10.
  5. Needles mined out, usually a tiny hole visible
    spruce needle miners; R1-P32, R3-P10, R5-P47, R8-P90, R17-P2.
    Larch: larch casebearer; R1-P36, R5-P49, R8-P88.
  6. Needles off color due to microscopic stippled areas, microscopic webbing may be present, individual mites very tiny, not usually visible to the naked eye except on a white background
    Spruce, junipers, arborvitae:

    spider mites; R1-P118, R3-P38, R5-P31, R17-P1.
  7. Needles with brown spots or dead ends
    Lophodermium needle cast; R2-P32, R6-P7, R13-P10.
    Winterburn; R2-P480, R9-P97, R10-P36.
    Pesticide/herbicide damage; R2-P456, R6-P118, R19-P6.
  8. Second year needles turning uniformly reddish, fading to straw colored and remaining on the branch for several years, elongate black fruiting bodies may be present on dead needles
    Lirula needleblight, R5-P15, R2-P42, R13-P14.
  9. Annually in late summer or fall, second or third year's needles uniformly turning brown to yellow and falling off (pines) or older branchlets of arborvitae turning reddish or brownish and falling off: natural foliar shedding; R2-P498.

II. Injury to Twigs or New Shoots

  1. Shoots dying, deformed or stunted
  1. New shoots stunted or dying
    Pines: Sphaeropsis (Diplodia) tip blight; R2-P136, R4-P128, R9-P65, R10-P54, R13-P11.
    Spruce:white pine weevil; R1-P54, R3-P23, R5-P73, R8-P96, R10-P68.
    Junipers:Kabatina tip blight; R2-P138, R4-P116.
  2. Shoots dead, sometimes into 2nd year growth, live and dead areas sharply delimited, resin soaked at the boundary only
    Scotch and mugo pine: Cenangium dieback, R2-P230.
  3. Buds and new shoots dying, being mined out
    pine tip moth; R1-P48, R3-P22, R8-P96.
  4. Buds being mined out, small pitch mass present
    Ponderosa pine: metallic pine pitch nodule maker; R3-P23, R8-98.
  5. Large aphids on twigs, branches or main stem
    Pines and spruce: giant conifer aphid; R3-P39.
  6. Single gall consisting of large numbers of chambers, near the base of new shoots
    eastern spruce gall adelgid; R1-P114, R3-P31, R5-P51, R8-P54, R9-P72.
  7. Individual galls grouped together on stems
    Spruce: spruce gall midge; R1-P116, R5-P45.

III. Injury to Trunks or Larger Branches

  1. Injury to branches
  1. Entire branches dying, lower branches first
    Spruce: Cytospora canker; R2-P196, R4-P132, R10-P53, R13-P14, R14-P3.
  2. Woody galls on branches of pines, surface ruptures in the spring revealing an orange to yellowish spore mass
    Ponderosa and Scotch pine: western gall rust; R2-P282, R4-P126, R6-P51, R9-P27, R10-P73, R12-P3, R13-P11.
  3. Irregular sized woody galls on junipers or red-cedars, may swell to large gelatinous mass in wet weather
    and red-cedars: cedar apple rust and other Gymnosporangium rusts; R2-P240, R4-P136, R6-P82, R10-P71, R12-P2, R13-P7, R14-P8.
  4. Large pitch masses in branch whorls or on the trunks of pines, may cause branch failure or stem breakage, pitch masses turn yellowish with age
    Pines: Zimmerman pine moth
    complex; R1-P48, R3-P24, R5-P85,
    R8-P98, R10-P84.
  5. Medium sized, similarily shaped pitch masses, or pitch tubes, lower bole of tree
    red turpentine beetle; R1-P62, R3-P25, R5-P79.
  6. Regular sized, evenly spaced rows of holes in the bark of the main trunk or large branches
    All species: sapsuckers (a woodpecker); R1-P500, R10-P83.
  7. Small regularly shaped tunnels under the bark, usually scoring both bark and wood, or a "shothole" pattern in the bark (bark beetles) R1-P250, R10-P82.
    Pines: pine engravers, (I ps sp), R1-P62, R5-P81.
    Spruces:spruce scolytus; Prunus: shothole borer and peach bark beetle; R1-P250.
  8. Witches'-brooms, clusters of shoots all orginating near the same point
    cedar apple rusts; R2-P240, R4-P136, R6-P82, R10-P71, R12-P2, R13-P7, R14-P8.
    Pines: Western gall rusts; R2-P282, R4-P126, R6-P51, R9-P27, R10-P73, R12-P3, R13-P11.

IV. Entire Tree Dying

  1. Dying with needles on
    Pines: Ips bark beetles; R1-P62, R5-P81.
    Red turpentine beetle; R1-P62, R3-P25, R5-P79.
    All species:chemical damage; R2-P456, R6-120.
    Herbicides or soil sterilents; R2-P340, R2-P456, R4-P33, R19-P6.
    Girdling by small rodents, beavers, or porcupines; R6-122.
    Mechanical damage from lawn mowers, string trimmers, weed barriers, ice; R2-P338, P19-P284.
    Girdling roots, etc. R2-488.
    Drought damage; R2-P340 & 476, R4-P88, R9-P98.
    Winter injury; R2-P478, R6-P115, R9-P97, R10-P38.