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:
- List of Annotated References on Tree Pests - Current references on
identification, injury symptoms and control/management of tree pests are listed.
- 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.
- 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.
- List of Common and Scientific Names of Woody Plant Pests - A cross reference of
various woody plant pests in North Dakota.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
- "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.
Introduction
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
- Needles being eaten
- Webbing present, (bud cap often retained by silk)
Spruce: spruce budworm; R1-P28, R5-15, R8-43, R17-P2. *
- 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.
- Needles damaged or missing, but not consumed, may be off color or have discolored
spots or bands or be mined out
- 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.
- 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.
- Needles with small waxy white spots
Pines and spruce: pine needle scale; R1-P108, R3-P38, R5-P41, R8-131, R9-P85,
R17-P2.
- Needles being mined out in the needle sheaths
Pines: tip moths; R1-P48, R3-P22, R8-P96.
pine needle sheath miner; R1-P38, R3-P10.
- Needles mined out, usually a tiny hole visible
Spruce: spruce needle miners; R1-P32, R3-P10, R5-P47, R8-P90, R17-P2.
Larch: larch casebearer; R1-P36, R5-P49, R8-P88.
- 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.
- Needles with brown spots or dead ends
Pines: 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.
- 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
Spruces: Lirula needleblight, R5-P15, R2-P42, R13-P14.
- 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
- Shoots dying, deformed or stunted
- 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.
- 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.
- Buds and new shoots dying, being mined out
Pines: pine tip moth; R1-P48, R3-P22, R8-P96.
- Buds being mined out, small pitch mass present
Ponderosa pine: metallic pine pitch nodule maker; R3-P23, R8-98.
- Large aphids on twigs, branches or main stem
Pines and spruce: giant conifer aphid; R3-P39.
- Single gall consisting of large numbers of chambers, near the base of new shoots
Spruce: eastern spruce gall adelgid; R1-P114, R3-P31, R5-P51, R8-P54, R9-P72.
- Individual galls grouped together on stems
Spruce: spruce gall midge; R1-P116, R5-P45.
III. Injury to Trunks or Larger Branches
- Injury to branches
- Entire branches dying, lower branches first
Spruce: Cytospora canker; R2-P196, R4-P132, R10-P53, R13-P14, R14-P3.
- 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.
- Irregular sized woody galls on junipers or red-cedars, may swell to large gelatinous
mass in wet weather
Junipers and red-cedars: cedar apple rust and other Gymnosporangium
rusts; R2-P240, R4-P136, R6-P82, R10-P71, R12-P2, R13-P7, R14-P8.
- 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.
- Medium sized, similarily shaped pitch masses, or pitch tubes, lower bole of tree
Pines: red turpentine beetle; R1-P62, R3-P25, R5-P79.
- 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.
- 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.
- Witches'-brooms, clusters of shoots all orginating near the same point
Junipers: 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
- 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.