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C O N T I N U I N G
!
KEEP
YOUR
TOOLS
SHARP
Hone Your
Diagnostic Skills
By Michael J. Raupp
LEARNING OBJECTIVES
The arborist will be able to
h Learn the primary ways insects and mites injure plants
h Learn which groups of insects are involved in plant
damage
h Link specific pest groups with the types of injury
they cause
h Recognize five general categories and several specific
categories of plant symptoms and signs
h Associate pests with symptoms and understand
how insects and mites create injury
E D U C A T I O N
CEUs for this article apply to Certified Arborist, Utility
Specialist, Municipal Specialist, Tree/Worker Climber,
and the BCMA practice category.
Diagnostic Skills
U N I T
Several skills increase the likelihood of making successful
diagnoses of plant problems. First, diagnosticians must have
a solid level of technical competence. This knowledge includes
being well-versed in identification of woody plants, plant
culture, and the causes of plant injury. Causes might include
abiotic, non-living factors such as drought, nutrient deficiencies, temperature extremes, and mechanical injuries, or
causes associated with biotic agents including insects, mites,
fungi, bacteria, viruses, phytoplasmas, and other living organisms. Second, successful diagnosticians will have keen
observational skills and the ability to discriminate between
what is normal for plant appearance and growth and what
is not. Finally, diagnosticians must have a sense of curiosity and a hunger to learn not only the types of plant injury,
but also their underlying causes (Davidson and Raupp 2009).
This article focuses on the first two attributes of the diagnostic process: how to recognize what is normal and what is
not, and how to recognize symptoms and signs associated with
insects and mites as they consume and inhabit trees and shrubs.
Symptoms and Signs
Most arborists are familiar with the terms symptoms and
signs and some use these terms interchangeably, but they
are truly different. Symptoms are how organisms like trees
respond to a disorder. Symptoms are usually non-specific,
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that is, a single symptom can have several causes. Take the
case of chlorotic or discolored leaves. We know that some
acid-loving plants, when grown in basic soils, are unable
to obtain sufficient nutrients from the soil. This may cause
leaves to be yellow rather than green. Exposure to airborne
pollutants or excessive concentrations of road salts may produce the same symptom. In addition to these abiotic factors,
high densities of sucking insects such as scales or spider
mites may also cause leaves to turn yellow. While discolored leaves are a symptom of underlying problems, careful
observation and further investigation are often necessary to
pin-down the true agent or agents underlying the symptom.
Signs are more direct and often provide definitive information when making a diagnosis. Signs are the organism
itself or direct products left behind by the organism. Signs
include adults, eggs, nymphs, larvae, pupae, cocoons, and
shed skins of insects. As insects move through the world,
they leave behind specific and easily identifiable objects of
their presence. These objects include silk, frass (a polite
term for what comes out the rear end of an insect or mite
as it feeds), protective wax, and exit holes in the bark or
leaves.
Develop a “CSI” Mentality
Insects damage plants by feeding, making protective refuges,
and laying eggs. Often, when one arrives at a tree of interest, the perpetrator of the injury has already fled the crime
scene. Frequently, only symptoms or signs may remain. Like
a crime scene investigator (CSI), you can use clues left behind
to help identify the perpetrator. Symptoms can point you in
the right direction and some signs are specific enough to reveal
the identity of the perpetrator. Of course, correct identification of the plant is vital to an accurate diagnosis. Knowledge
of the life cycle of the pest will help link the timing of the
plant injury to the seasonal activity of the pest. Accurate identification will enable you to design the right strategy for managing the pest in the most timely and efficacious way. This
approach to diagnostics is called “symptomatology,” and was
first described for use in arboriculture by Carlton S. Koehler
in the Journal of Arboriculture (1987).
How Bugs Injure Plants: The Weapons
Perpetrators of crimes use weapons. The primary weapons
of insects and mites are their mouthparts. The direct result
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plants, insects such as mosquitoes and fleas suck blood
from animals through piercing mouthparts. Butterflies and
some moths are unique in having strange, highly modified
mouthparts. Elongated maxillae are coiled at rest and uncoil
when a butterfly finds a suitable flower in which to insert
its proboscis to sip nectar.
A relatively rare but nonetheless important way that
insects injure plants is through egg-laying activities. Cicadas
are the best-known perpetrators of this offense. After emerging from the earth, shedding their skins, flying to the treetops and mating, female cicadas use a strong egg-laying
tube called an ovipositor to insert eggs into the woody tissues of small branches. Where cicadas are abundant, these
wounds may cause limbs to flag and snap off the tree. Even
wounds that are compartmentalized may be structurally
deficient in later years or serve as entry points for pathogens.
The tree hopper, a cicada-relative, also oviposits in small
branches and may cause minor injury.
Matching Perpetrators to their Mouths
D
FEBRUARY 2010
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13
U N I T
One recent textbook of Entomology lists about 30 different
large related groups of insects called orders. Fortunately, for
arborists, only a few orders of insects create the vast majority
of injury to trees and shrubs. To identify a perpetrator, it is
often helpful to link a category of damage to a type of mouthpart. The next step in the diagnostic process is to use the
information on mouthparts as an important clue to the
identity of the perp. So far, we have described two major
categories of mouthparts, chewing and sucking. Now the
question becomes, what insect has which type of mouthpart? The most common groups of plant feeding insects with
chewing mouthparts are the immature stages of moths and
butterflies (Order: Lepidoptera) commonly called caterpillars,
the larvae of sawflies (Order: Hymenoptera), and larvae
(grubs) and adults of beetles (Order: Coleoptera). Occasionally,
grasshoppers and some crickets (Order: Orthoptera) and
earwigs (Order: Dermaptera) damage herbaceous and
E D U C A T I O N
of an insect eating a plant is injury. How that injury reduces
the quality, appearance, or value of the plant is damage.
Although these terms are not synonymous, we will use them
interchangeably in this article. To understand how feeding
injures plants, we must first understand how insects’ mouthparts work. The most primitive type is chewing mouthparts.
Chewing mouthparts consist of six distinct external parts. The
forward-most part is a front “lip” called the labrum. This
unpaired structure occurs at the front of the insect’s face.
Lateral and just behind the labrum are the mandibles. These
paired structures are the actual jaws that cut and tear leaves,
bark, and wood and create chewing injury. Just behind the
mandibles are another set of paired appendages called the
maxillae. These specialized appendages are loaded with sensory
structures that evaluate the quality of potential food. Maxillae
assist in shoving cut leaves or other plant tissues into its gullet.
Finally, at the back of the head is an unpaired structure
called the labium or back “lip.” All of the mouthparts can
move independently in coordinated ways to cut leaves and
woody tissues and to move them into the digestive tract.
As insects evolved and became more specialized, some
groups developed a type of mouthpart known as sucking
or piercing. In sucking insects such as aphids and plant bugs,
the labium is often reduced in size and inconspicuous. Greatly
elongated mandibles and maxillae form the tissue-penetrating
structures of the beak, also known as the proboscis. These
piercing stylets enter the tissue of the plant. The maxillae
join and internal structures create two channels within the
beak. One channel is a salivary duct capable of injecting
saliva into the plant to liquefy plant tissues. A small hydraulic
pump found within the head of the insect sucks the partially digested liquid nutrients back up through the beak
into the digestive tract. Mandibles and maxillae are enclosed
in a jointed labium that folds back when the piercing
stylets are inserted into the plant.
Many variations of sucking mouthparts exist within the
insect world. In addition to insects that consume tissues of
C O N T I N U I N G
Coarse chewing damage caused by cankerworms in spring (pictured here), will stay with this oak all season.
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C O N T I N U I N G
woody plants, but these groups are rarely important pests
of trees and shrubs in North America.
Sucking mouthparts belong to immature and adult stages
of the mega-order of insects called the Hemiptera. These
insects have gradual metamorphosis meaning that they lack
larval and usually pupal stages. Nymphs are the active immature stages of Hemiptera. Hemiptera includes some of our
most pernicious pests, such as aphids, scales, adelgids, whiteflies, mealybugs, leafhoppers, spittlebugs, stinkbugs, lace
bugs, and plant bugs. Mites are also noteworthy. They are
not insects, but belong to a large group of arthropods called
the arachnids. Their kin are spiders, scorpions, and ticks.
The mouthparts of mites consist of piercing stylets that
rupture cells. The mite imbibes plant fluids. Therefore, the
modus operandi of mites and resultant injury to plants are
quite similar to that caused by sucking insects.
E D U C A T I O N
Sucking insects like Andromeda lace bug cause stippling, and
discolor leaves by removing cell contents and turning green
tissues white.
Linking Symptoms and Signs
to Insects and Mites
U N I T
Symptoms and signs of insects and mites comprise five major
categories: chewing damage, discoloration, distortion, dieback, and products. Diagnosticians can use these clues to
narrow the search for a perpetrator by associating a type of
mouthpart with the damage category it causes. By knowing
the type of mouthpart, the list of potential villains is narrowed greatly. Certain insects attack only a limited range of
plants, such as a single plant family or genus. By correctly
identifying the host plant involved, and looking at damage
symptoms and signs, a skilled diagnostician can often identify the cause of a problem, even though the pests are difficult to find or may no longer be present.
The following outline of pest damage symptoms and
signs provides a guide for diagnosticians to increase their
efficiency and effectiveness in visually diagnosing the causes of insect and mite injury. Be aware that leaves may
exhibit more than one type of symptom simultaneously.
Usually, several different pests will attack a plant during a
single growing season. This results in several categories of
damage appearing on an individual leaf or tree at the same
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time. One pest like a caterpillar may remove portions of the
leaf blade with chewing mouthparts and another like a gall
wasp may distort the normal shape of a leaf. Furthermore,
sometimes a single pest may cause multiple categories of
damage. For example, aphids may distort leaves and discolor
leaves. As aphids feed, they excrete honeydew, an insect
product. Their shed skins often adhere to plants. Aphids
are one pest creating three different categories of damage.
Chewed Leaves or Blossoms
This damage category by definition involves insects with
chewing mouthparts; therefore, the list of potential insect
perpetrators distills immediately to caterpillars, sawfly larvae,
or beetles as the most likely suspects. Occasionally, some
grasshoppers and crickets will damage leaves, but the impact
of them on trees is minor. Earwigs chew leaves of herbaceous plants. The primary categories of defoliation and some
associated perpetrators include the following:
Defoliation—Large portions of leaf blades or needles or
entire leaves disappear. The common suspects include large
caterpillars, sawflies, and grasshoppers.
Hot holes—Small, distinct holes in leaf blades are usually
the work of small caterpillars and leaf beetles with tiny jaws
capable of removing only small pieces of tender leaves.
Margins notched—This clue is highly characteristic of
weevils like black vine weevil, two-banded Japanese weevil,
Fuller rose beetle, and strawberry root weevil. These beetles
work the margins of leaf blades leaving behind easily recognized notching on broad-leaved evergreens such as rhododendrons, ivy, and laurel. Several small species of weevils create winding notches on the leaves of deciduous trees.
An alien caterpillar recently introduced to Maryland and
Virginia creates similar damage on euonymus.
Skeletonization—Many beetles and some sawfly larvae and
caterpillars have small jaws. Rather than consuming entire
leaf blades, these chewers remove only the epidermis and
soft tissues between leaf veins leaving only the “skeleton” of
the leaf intact. Skeletonization often appears a bit later in the
growing season when foliage is mature and tough. It is the
classic damage associated with larvae and adults of elm leaf
beetle and Japanese beetle. Some very small caterpillars such
as oak leaf skeletonizers also create this damage. A variant
of skeletonization results in one epidermal surface and leaf
veins remaining. Etching is the name of this symptom.
Discolored Leaves or Blossoms
The magnificent process of photosynthesis depends on a
green pigment called chlorophyll and the normal color of
most leaves is green with exceptions found in cultivars that
may be red, yellow, or variegated. Many insects with sucking mouthparts consume the liquid contents of plant cells
removing the green coloration and leaving behind areas of
white or yellow that may turn brown. The majority of insects
associated with the symptom of discoloration belong to
the clan of plant bugs, scales, aphids, and their kin. Mites,
including spider mites and rust mites, also cause discoloration. Primary categories of discoloration and the associated
perpetrators are listed on the following page.
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Tiny wasps, such as this horned oak gall cynipid, distort
plant parts by disrupting the normal development of tissues.
Stippling—Small white dots or speckles result where insects
or mites with piercing mouthparts remove some contents of
cells. Spider mites and their tiny relatives the eriophyid
mites create very fine spots that may coalesce and turn entire
leaves or needles yellow, russet, or brown. Lace bugs, plant
bugs, and leafhoppers create larger stipples that often remain
quite distinct.
Streaking—Small insects called thrips also have modified
sucking mouthparts. Some species feed in linear rows creating silvery streaks on leaves.
Leaf cupping and curling—Probing mouthparts of sucking insects such as the boxwood psyllid and many species
of aphids damage leaves before they expand, causing them
to cup or curl. Cupped leaves of boxwood provide a home
for immature stages of boxwood psyllid. Once deformed,
leaves remain so even after the perpetrator is long gone
until the plant sheds them.
Leaf or twig galling—Many species of small wasps, sawflies, flies, aphids, psyllids, thrips, and mites cause galls on
leaves, stems, flowers, and roots.
Bark rippling or cracking—Borers that consume the cambium and vascular tissues beneath tree bark may cause
deformation of branches or the trunk. Rippling on the bark
of trees like paper birch may be a defensive response as the
tree creates callus tissue to encapsulate the larvae. Borers
that kill cambium (e.g., emerald ash borer) cause vertical
E D U C A T I O N
Mining—Several orders of insects have adapted to life between
the upper and lower epidermal surfaces of leaves. This clever
adaptation helps them avoid many predators that roam the
leaf’s dangerous surface. Some leafminers like the leaf-mining
flies boxwood leafminer and native holly leafminer, have
mouthparts that puncture cells. Others use chewing mouthparts to access nutritious contents of cells. Larvae of sawflies
like birch leafminer, beetle larvae like locust leafminer, and
caterpillars like tupelo leafminer cause damage in this way.
The shape of a leafminer’s mine can be quite diagnostic.
Native holly leafminer creates a sinuous trail called a serpentine mine as it feeds and grows in leaves of holly. Larvae
of the birch leafminer create an irregular blotch. Sometimes
the dead tissue associated with a leafminer will drop from
the leaf leaving behind an irregular hole as in the case of
tupelo leafminer.
Yellowing—As aphids, scales, whiteflies, and mealybugs
feed on the undersides of leaves and needles, diffuse yellow
patches may appear on both the top and bottom surfaces
of leaves. When sucking insects or mites are very abundant,
leaves on entire branches or trees may appear yellow or
brown rather than green.
Distorted Leaves, Branches, or Trunks
Many larvae of flatheaded borers, like the bronze birch borer,
feed beneath the bark and kill cambium which soon results
in dieback in the canopy.
D
FEBRUARY 2010
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U N I T
Distortion is most likely to occur when an insect or mite
consumes undifferentiated and actively growing plant tissues such as buds of shoots, leaves, flowers, roots, or actively
dividing cells associated with vascular tissues. Often sucking mouthparts of aphids, adelgids, psyllids, and mites create
this symptom. Some insects and mites secrete plant hormones that mimic and act as growth factors to alter the
normal development of a plant part, such as a leaf. For
example, tiny wasps called cynipids lay eggs in expanding
C O N T I N U I N G
leaves of oaks. Cynipid larvae cause the leaf to develop
strange structures shaped like balls of wool, small bullets,
or gnarly apples festooned with tiny horns. These abnormal growths are called galls. Primary categories of deformation and associated perpetrators include the following.
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C O N T I N U I N G
cracks to form in the bark. When borers kill cambium, bark
is not produced adjacent to the damaged tissue. As the rest
of the tree increases in girth, bark separates and splits where
underlying cambium has died. Insects like cicadas that
oviposit in branches create cracks that remain for several
years before closing.
Dieback of Shoots, Twigs, or Branches
E D U C A T I O N
Dieback in the canopy often results from damage to a tree’s
vascular system such as phloem and xylem tissue derived
from the cambium. When dieback is observed, look down.
Remember, trees obtain water and nutrients from the soil
and transport them to the canopy via the vascular tissue.
Construction can sever roots. Heavy equipment can compact soils and greatly reduce vital air spaces thereby limiting
the penetration of air and water needed by roots. Installing
trees too deep or in sites prone to waterlogging may condemn roots to an anaerobic death. Volcano mulch may also
create conditions unfavorable to roots. When roots die, so
too will branches they support. Inspect the bole of the tree
to rule out girdling roots, embedded wires, and assaults to
the bark caused by weed whackers, lawn mowers, and vehicles. Once obvious abiotic factors have been eliminated as
a cause, look for symptoms and signs left behind by insects.
A few categories of dieback and the usual suspects include
the following:
Shoot dieback—Many caterpillars and beetles, and some
sawfly larvae, use powerful jaws to bore down the centers of
shoots from the tip toward the base causing tips of branches
to wither and die. Classic examples include tip moths such
as the Nantucket pine tip moth and European pine shoot
moth that attack conifers.
Branch dieback—Perpetrators responsible for this damage
are strong-jawed boring beetles such as flatheaded borers
(e.g., emerald ash borer, bronze birch borer, two-lined chestnut borer), roundheaded borers (e.g., Asian longhorned
beetle, rounded headed apple tree borer, Eucalyptus longhorned beetle, twig girdler), a huge array of bark beetles
(e.g., mountain pine beetle, southern pine beetle, ambrosia
beetles), boring caterpillars (e.g., dogwood borer, banded
ash clearwing, sequoia pitch moth), and wood wasps (e.g.,
Sirex wood wasp) to name a few. Many of these attack tree
trunks, but by causing mayhem with vascular tissues or
killing cambium in the trunk, branches will also die. Sometimes sucking insects like armored scales and adelgids achieve
high densities on branches and trunks. Combined damage
of thousands of tiny stylets may rob plants of nutrients, damage vital tissues, and cause dieback. Egg-laying of cicadas may
cause branches distal to the injury to turn brown and die.
Products of Insects
U N I T
Insects and mites excrete waste. They also produce protective and supportive materials such as wax and silk. These
signs are often highly reliable clues to the identity of a pest.
Products of insects and mites include the following:
Honeydew and sooty mold—Many insects with sucking
mouthparts process vast quantities of plant liquids to obtain
enough nutrients to support growth and development. Waste
16
Wax is the hallmark of many sucking insects, such as aphids,
scales, mealybugs, and adelgids like the Cooley spruce gall
adelgid seen here on Douglas fir.
liquid is rapidly excreted as a product called honeydew by
many aphids, soft scales, leafhoppers, tree hoppers, plant
hoppers, whiteflies, psyllids, and mealybugs. This sugarrich product is a substrate for the growth of sooty mold, a
non-pathogenic fungus that can cloak leaves with an ugly
sooty coat. When you see sooty mold on leaves, look up
to see what is producing it.
Fecal spots and frass—Fecal spots often remain on leaves
even after the perpetrator is gone. Fecal spots, sometimes
called tar spots, are excellent clues for the presence of many
sucking insects such as lace bugs, thrips, some plant bugs,
and leaf beetles. Frass is the sawdust-like remains of processed
leaf and wood tissue that has traveled through the digestive
tract of chewing insects like beetles and caterpillars. Pellets
of frass are sometimes clues of an infestation such as those
that rain from canopies of oaks when gypsy moths are present. Many wood-boring beetles like Asian longhorned beetle,
and caterpillars like banded ash clearwing, expel frass from
their galleries as they feed. Others like emerald ash borer
pack frass behind them in their gallery beneath the bark of
the tree.
Silk—Caterpillars produce silk. The structure and location
of a silken gallery or tent provides a useful clue to the identity tent caterpillars, webworms, and leaftiers. For example,
tents in the crotches of cherry trees in spring are signs of
eastern tent caterpillars and tents at the tips of walnut in
late summer indicate fall webworm. At high densities spider mites also produce fine webs of silk.
Protective cases composed of plant parts—Bagworms and
case bearers are caterpillars notorious for incorporating plant
parts into the silk of their protective bags and cases.
Fluffy white wax—Wax is a hallmark of many sucking insects
like adelgids, mealybugs, some aphids, many whiteflies, some
psyllids, and some scale insects.
Soft or hard wax colored white, brown, gray to black—
Armored scales are tiny sucking insects that secrete a protective cover of wax. Covers often match the color of bark
making diagnosis difficult even when scales are at damaging levels.
Spittle—Spittlebugs are relatives of leafhoppers and they secret
frothy protein that looks like spit. Most species of spittlebugs
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ARBORIST•NEWS
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Literature Cited
Davidson, J.A., and M.J. Raupp. 2009. Managing insects
and mites on woody plants: An IPM approach. Tree
Care Industry Association, Londonderry, N.H. 197 pp.
Koehler, C.S. 1987. Symptomatology in the instruction of
landscape ornamentals entomology. Journal of Arboriculture
13:78-80.
Michael Raupp is a Professor of Entomology, Extension Specialist,
and bug geek at the University of Maryland - College Park,
who has worked with arborists for three decades to develop
IPM and PHC programs. Visit his website online
(www.BugOfTheWeek.com).
Photos courtesy of the author.
CEU TEST QUESTIONS
Take your quiz online! Go to www.isa-arbor.com/certification/ceus.aspx and click on “Arborist News Quizzes Online.”
If you need a login and password, send an e-mail to [email protected].
To receive continuing education unit (CEU) credit (1.0 CEU) for home study of this article, after you have read it, darken the
appropriate circles on the answer form of the insert card in this issue of Arborist News. (A photocopy of the answer form is not acceptable.)
A passing score for this test is 16 correct answers.
Next, complete the registration information, including your certification number, on the answer form and send it to ISA, P.O.
Box 3129, Champaign, IL 61826-3129. Answer forms for this test, Keep Your Tools Sharp! Hone Your Diagnostic Skills, may
be sent for the next 12 months.
If you do not pass the quiz, ISA will send you a retake answer sheet. You may take the quiz as often as necessary to pass. If you
pass, you will not be notified; rather, you will see the credit on your CEU report (available online). Processing CEUs takes 4 to 6 weeks.
1. Abiotic causes of plant injury include
a. insects
b. drought
c. mites
d. fungi
2. The least important skill of a diagnostician would be
a. ability to identify plants
b. recognizing abnormal leaf color
c. a high level of curiosity
d. ability to apply use tree injection
systems
3. Symptoms
a. always have a single cause
b. are the same as signs
c .may be caused by several factors
d. are not typically useful in
diagnostics
5. Which of the following is not a
structure of chewing mouthparts?
a. maxillae
b. antennae
c. mandible
d. labium
FEBRUARY 2010
7. Cicadas injure plants by
a. laying eggs in twigs
b. chewing leaves
c. webbing leaves together
d. mining leaves
8. Which of the following lack chewing
mouthparts?
a. caterpillars
b. beetle larvae
c. sawfly larvae
d. adelgids
9. Which of the following lack sucking
mouthparts?
a. aphids
b. psyllids
c. grubs
d. scales
10. Defoliation is
a. mostly likely cased by a large
caterpillar
b. a clear symptom of aphids
c. the result of cicada feeding
d. wax produced by scales
11. When tissue of the leaf blade is
removed leaving only veins behind,
the injury is called
a. shot holes
b. notching
c. gummosis
d. skeletonization
12. Notched leaf margins are usually
caused by
a. weevils
b. aphids
c. roundheaded borers
d. sawfly larvae
13. Which of the following groups lack
members that mine leaves?
a. sawflies
b. lace bugs
c. flies
d. beetles
14. Insects that cause distortion usually
attack
a. mature leaves
b. undifferentiated tissues
c. bark
d. ripened fruit
D
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17
U N I T
4. Which of the following is unlikely to
be a sign?
a. a gypsy moth egg mass
b. dieback of a branch
c. fecal spots of lace bugs
d. shed skins of aphids
6. In sucking mouthparts, where would
the salivary duct be found?
a. labrum
b. maxillae
c. mandible
d. labium
E D U C A T I O N
CEUs for this article apply to Certified Arborist, Utility Specialist, Municipal Specialist, Tree/Worker Climber, and the BCMA practice
category.
C O N T I N U I N G
cause little or no injury to plants other than their disagreeable appearance.
Pitch tubes, pitch masses, gummosis, and sap flow—
These clues are not directly produced by an insect. They
are the plant’s response to mechanical wounding and are
often closely associated with insect attack. Pine trees and
other conifers have pressurized resin canals as part of their
defensive arsenal. Upon entry, bark beetles puncture resin
canals, releasing resin that can entrap and physically expel
the invader. The resin accumulates and hardens to form
pitch tubes extending from the bark. Pitch tubes are good
indicators of attack by bark beetles. Pitch masses are common on branches and terminals of conifers and thick flows
of sap called gummosis are often seen on deciduous trees when
insects with jaws like caterpillars and beetle larvae attack.
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C O N T I N U I N G
15. Common gall formers include
aphids, sawflies, mites, and
a. adult beetles
b. caterpillars
c. tree hoppers
d. cynipid wasps
16. Which of the following is most likely
to cause dieback?
a. gyspy moth caterpillars consuming oak leaves
b. aphids on the leaf of a linden
c. boxwood psyllids feeding on the
terminals of boxwood
d. emerald ash borer feeding on
cambium of green ash
17. Honeydew is produced by
a. aphids
b. beetles
c. sawflies
d. leafminers
18. Frass is not produced by
a. emerald ash borer
b. gypsy moth
c. Asian longhorned beetle
d. armored scales
E D U C A T I O N
19. Silk is produced by caterpillars and
a. beetle larvae
b. adult flies
c. spider mites
d. aphids
20. Pitch tubes often indicate the
presence of
a. bark beetles
b. bagworms
c. leafminers
d. sawfly larvae
Guide for Plant
Appraisal,
9th Edition
Authored by the Council of Tree and
Landscape Appraisers, Guide for Plant
Appraisal, 9th Edition, is the professional plant appraiser’s how-to manual
for determining size, species, condition,
and location factors that influence the
value of plants. Not only is it an invaluable source for establishing the evaluation
of plant casualties, but the guide is
also a reference for real estate transactions, insurance purposes, plant
condemnation actions, and tree inventories. (Please note that special
ratings lists are available from local chapters.) © 2000, softcover, 143 pp.
#P1209 • Retail Price: $125.00 • Member Price: $75.00
Guide for Plant Appraisal Workbook
A highly recommended learning tool, this workbook is designed to
accompany appraisal methods. Use this workbook for practical
experience working through sample appraisal problems as well as
using calculations necessary for determining evaluations. © 2000, 12 pp.
#W1209 • Retail Price: $25.00 • Member Price: $15.00
TO ORDER, CALL 1-888-ISA-TREE
OR VISIT US ONLINE AT WWW.ISA-ARBOR.COM/STORE
TREE HEALTH • SAFETY • ROPES AND KNOTS • CLIMBING
Tree Climbers’ Guide
(3rd Edition)
By Sharon Lilly
U N I T
Written specifically from the tree climber’s perspective to learn safe climbing
and aerial tree work principles, this publication may be used as a basic text
for tree climbers as well as a study guide for the ISA Certified Tree Worker/
Climber Specialist exam. Each chapter includes a list of key terms and
concludes with a workbook section. The chapter topics, enhanced with more
than 200 color illustrations, include: Tree Health and Sciences, Safety, Ropes
and Knots, Climbing, Pruning, Rigging, Removal, and Cabling. The guide also
contains appendices with answers to the workbook questions, a glossary,
and resources listed for further reference. (©2005, softcover, 172 pp.,
glossary, appendices, index)
#P1230 (English) • #P1230S (Spanish)
Retail Price: $59.95 • ISA Member Price: $49.95
TO
ORDER, CALL
1-888-ISA-TREE
OR VISIT US ONLINE AT WWW.ISA-ARBOR.COM/STORE
TREE SCIENCES • PRUNING • IN ENGLISH OR SPANISH
18
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